Posted on by Matt Williams

What are Cepheid Variables?

Hubble image of variable star RS Puppis (NASA, ESA, and the Hubble Heritage Team)

The Universe is a really, really big place. We’re talking… imperceptibly big! In fact, based on decades worth of observations, astronomers now believe that the observable Universe measures about 46 billion light years across. The key word there is observable, because when you take into account that which we cannot see, scientists think it’s actually more like 92 billion light years across.

The hardest part in all of this is making accurate measurements of the distances involved. But since the birth of modern astronomy, increasingly accurate methods have evolved. Aside from redshift and examining the light coming from distant stars and galaxies, astronomers also rely on a class of stars known as Cepheid Variables (CVs) to determine the distance of objects within and beyond our Galaxy.

Definition:

Variable stars are essentially stars that experience fluctuations in their brightness (aka. absolute luminosity). Cepheids Variables are special type of variable star in that they are hot and massive – five to twenty times as much mass as our Sun – and are known for their tendency to pulsate radially and vary in both diameter and temperature.

What’s more, these pulsations are directly related to their absolute luminosity, which occurs within well-defined and predictable time periods (ranging from 1 to 100 days). When plotted as a magnitude vs. period relationship, the shape of the Cephiad luminosity curve resembles that of a “shark fin” – do its sudden rise and peak, followed by a steadier decline.

The name is derived from Delta Cephei, a variable star in the Cepheus constellation that was the first CV to be identified. Analysis of this star’s spectrum suggests that CVs also undergo changes in terms of temperature (between 5500 – 66oo K) and diameter (~15%) during a pulsation period.

Use in Astronomy:

The relationship between the period of variability and the luminosity of CV stars makes them very useful in determining the distance of objects in our Universe. Once the period is measured, the luminosity can be determined, thus yielding accurate estimates of the star’s distance using distance modulus equation.

This equation states that: m – M = 5 log d – 5 – where m is the apparent magnitude of the object, M is the absolute magnitude of the object, and d is the distance to the object in parsecs. Cepheid variables can be seen and measured to a distance of about 20 million light years, compared to a maximum distance of about 65 light years for Earth-based parallax measurements and just over 326 light years for the ESA’s Hipparcos mission.

Calibrated Period-luminosity Relationship for Cepheids
Calibrated Period-luminosity Relationship for Cepheids. Credit: NASA

Because they are bright, and can be clearly seen million of light years away, they can be easily distinguished from other bright stars in their vicinity. Combined with the relationship between their variability and luminosity, this makes them highly useful tools in deducing the size and scale of our Universe.

Classes:

Cepheid variables are divided into two subclasses – Classical Cepheids and Type II Cepheids – based on differences in their masses, ages, and evolutionary histories. Classical Cepheids are Population I (metal-rich) variable stars that are 4-20 times more massive than the Sun and up to 100,000 times more luminous. They undergo pulsations with very regular periods on the order of days to months.

These Cepheids are typically yellow bright giants and supergiants (spectral class F6 – K2) and they experience radius changes in the millions of kilometers during a pulsation cycle. Classical Cepheids are used to determine distances to galaxies within the Local Group and beyond, and are a means by which the Hubble Constant can be established (see below).

Type II Cepheids are Population II (metal-poor) variable stars which pulsate with periods of typically between 1 and 50 days. Type II Cepheids are also older stars (~10 billion years) that have around half the mass of our Sun.

Type II Cepheids are also subdivided based on their period into the BL Her, W Virginis, and RV Tauri subclasses (named after specific examples) – which have periods of 1-4 days, 10-20 days, and more than 20 days, respectively. Type II Cepheids are used to establish the distance to the Galactic Center, globular clusters, and neighboring galaxies.

There are also those that do not fit into either category, which are known as Anomalous Cepheids. These variables have periods of less than 2 days (similar to RR Lyrae) but have higher luminosities. They also have higher masses than Type II Cepheids, and have unknown ages.

A small proportion of Cepheid variables have also been observed which pulsate in two modes at the same time, hence the name Double-mode Cepheids. A very small number pulsate in three modes, or an unusual combination of modes.

History of Observation:

The first Cepheid variable to be discovered was Eta Aquilae, which was observed on September 10th, 1784, by English astronomer Edward Pigott. Delta Cephei, for which this class of star is named, was discovered a few months later by amateur English astronomer John Goodricke.

Hubble image of variable star RS Puppis (NASA, ESA, and the Hubble Heritage Team)
Hubble image of variable star RS Puppis, one of the brightest known Cepheid variable stars in the Milky Way galaxy. Credit: NASA/ ESA/Hubble Heritage Team

In 1908, during an investigation of variable stars in the Magellanic Clouds, American astronomer Henrietta Swan Leavitt discovered the relationship between the period and luminosity of Classical Cepheids. After recording the periods of 25 different variables stars, she published her findings in 1912.

In the following years, several more astronomers would conduct research on Cepheids. By 1925, Edwin Hubble was able to establish the distance between the Milky Way and the Andromeda Galaxy based on Cepheid variables within the latter. These findings were pivotal, in that they settled the Great Debate, where astronomers sought to established whether or not the Milky Way was unique, or one of many galaxies in the Universe.

By gauging the distance between the Milky Way and several other galaxies, and combining it with Vesto Slipher’s measurements of their redshift, Hubble and Milton L. Humason were able to formulate Hubble’s Law. In short, they were able to prove that the Universe is in a state of expansion, something that had been suggested years prior.

Further developments during the 20th century included dividing Cepheids into different classes, which helped resolve issues in determining astronomical distances. This was done largely by Walter Baade, who in the 1940s recognized the difference between Classical and Type II Cepheids based on their size, age and luminosities.

Limitations:

Despite their value in determining astronomical distances, there are some limitations with this method. Chief among them is the fact that with Type II Cepheids, the relationship between period and luminosity can be effected by their lower metallicity, photometric contamination, and the changing and unknown effect that gas and dust have on the light they emit (stellar extinction).

These unresolved issues have resulted in different values being cited for Hubble’s Constant – which range between 60 km/s per 1 million parsecs (Mpc) and 80 km/s/Mpc. Resolving this discrepancy is one of the largest problems in modern cosmology, since the true size and rate of expansion of the Universe are linked.

However, improvements in instrumentation and methodology are increasing the accuracy with which Cepheid Variables are observed. In time, it is hoped that observations of these curious and unique stars will yield truly accurate values, thus removing a key source of doubt about our understanding of the Universe.

We have written many interesting articles about Cepheid Variables here at Universe Today. Here’s Astronomers Find New Way to Measure Cosmic Distances, Astronomers Use Light Echo to Measure the Distance to a Star, and Astronomers Closing in on Dark Energy with Refined Hubble Constant.

Astronomy Cast has an interesting episode that explains the differences between Population I and II stars – Episode 75: Stellar Populations.

Sources:

Posted on by Nancy Atkinson

New Shepard Defies The Odds And Sticks Landing

Screenshots of the ignition of the crew escape abort motor 45 seconds into the flight. Credit: Blue Origin/John Gardi.

Blue Origin successfully conducted an in-flight test of the New Shepard crew escape system on Wednesday. A live webcast featured stunning views of the crew capsule blasting away from the rocket booster 45 seconds into the flight with a two-second burn, and then parachuting safely back down to the ground. “We’re speechless right now and absolutely rightfully so,” said launch commentator Ariane Cornell.

Adding to the excitement, the rocket booster unexpectedly also survived the test, returning intact and making a successful vertical landing back at Blue Origin’s West Texas facility. So, yes, we were wrong about it ending in ‘fiery destruction.’ Blue Origin founder Jeff Bezos had said computer simulations showed a minimal chance the booster could survive the stresses of “70,000 pounds of off-axis force delivered by searing hot exhaust,” from the capsule escape motor, and then successfully return and land vertically as it’s done previously.

Bezos was pumped about the outcome, tweeting “That is one hell of a booster,” and included this Vine video of the event:

This is the fifth launch and landing of this rocket, the fourth made just this year. The successful landing of the booster means the intact rocket will find a place of honor – perhaps in a museum or even as a lawn ornament at Blue Origin, as SpaceX did.

Here’s the webcast:

This is the fifth launch and landing of this rocket, the fourth made just this year. The successful landing of the booster means the intact rocket will find a place of honor – perhaps in a museum or even as a lawn ornament at Blue Origin, as SpaceX did.

The escape system is designed to safely separate the New Shepherd crew capsule from the rocket booster in the event of an anomaly during flight, protecting a future crew. The abort system performed as expected, as about 45 seconds after liftoff, the escape motor ignited underneath the crew capsule. The motor burned for two seconds and shot the capsule up and away from the rocket booster. After a bit of tumbling – which would have given any occupants inside a fairly wild ride –the capsule’s parachutes deployed, allowing it to land safely. It will be interesting to hear followup on the tumbling from Blue Origin’s engineers, to see how unexpected that might be.

Cornel said this was a nominal test, providing an “exhilarating but safe ride.”

Screen capture of New Shepard booster touching down. Credit: Blue Origin.
Screen capture of New Shepard booster touching down. Credit: Blue Origin.

Once it was obvious the booster survived the blast from the escape system, it was fun and nail-biting to watch the booster reach the edge of space and then begin its descent. It used a series of braking maneuvers then just 8 minutes after launch as it approached the ground –still vertical — its BE-3 engine turned on and the landing legs deployed. The booster – looking only a little worse for wear — touched down gently.

Cornell said both the capsule and the booster will be retired, earning another turtle stencil.

Blue Origin stencils a tortoise on their vehicles after each successful flight. The tortoise is part of the company's Coat of Arms. Credit: Blue Origin.
Blue Origin stencils a tortoise on their vehicles after each successful flight. The tortoise is part of the company’s Coat of Arms. Credit: Blue Origin.

Blue Origin hopes to launch paying passengers into suborbital space by 2018 and today’s successful test means the company is on track to make it so.

Today’s successful test flight won praise from many in the industry. Eric Stallmer, presdient of the Commercial Spaceflight Federation congratulated the Blue Origin team and said, “Today’s fifth successful flight proved the New Shepard’s most critical safety features, innovative escape system technologies, and overall robustness of their system. It’s an exciting time to see these fantastic technological advancements and to witness the power of commercial industry.”

Screen capture of the New Shepard just before and after the abort motor ignition 45 seconds into the flight. Credit: Blue Origin/John Gardi.
Screen capture of the New Shepard just before and after the abort motor ignition 45 seconds into the flight. Credit: Blue Origin/John Gardi.
Posted on by David Dickinson

Seeing Double: Jupiter Returns at Dawn

double shadow transit
Io and Europa cast simultaneous shadows on Jupiter on March 22nd, 2016. Image credit and copyright: Andrew Symes.

Missing Jove? The largest planet in our solar system is currently on the far side of the Sun and just passed solar conjunction on September 26th, 2016. October now sees Jupiter slowly return to the dawn sky. Follow that gas giant, as an interesting set of double shadow transits transpires in late October leading in to early November.

This particular cycle of double shadow transits involves the large Jovian moons of Europa and Ganymede.

The scene on October 24th at 23:55 UT. Image credit: Created using Starry Night Education software.
The scene on October 24th at 23:55 UT. Image credit: Created using Starry Night Education software.

Europa and Ganymede double shadow transit season begins later this month, as both cast shadows on the Jovian cloud tops. This series of simultaneous shadow transits runs from October 17th to November 8th, and includes four weekly events.

The inner three large moons Io, Europa and Ganymede are in a 4:2:1 resonance. Europa orbits Jove once every 3.6 days and makes two circuits for Ganymede’s one. This means there’s a double shadow transit once every week in the current season:

The double shadow transit season of 2016. Created by author.
The double shadow transit season of 2016. Created by author.

When can you first spy Jupiter, post solar conjunction? Catching this particular series of double shadow transits is challenging this time around, owing to the planet’s position low in the dawn twilight. The first event on October 17th starts with Jupiter just 16 degrees west of the Sun, and the cycle ends with Jove 38 degrees west of the Sun on November 8th.

Keep in mind, it is possible to track Jupiter up in to the daytime sky, post sunrise. To do this, you’ll need a ‘scope with a solid equatorial mount and good sidereal tracking. The trick is to lock on to Jupiter before sunrise and track it up in to the dawn sky. Be sure to physically block that dazzling rising Sun out of view behind a hill or building, and NEVER aim your telescope at the Sun!

Using this method opens up the possibility of nabbing a given double shadow event to longitudes due east of the quoted locales above.

The waning crescent Moon also passes 1.4 degrees NNE of Jupiter on October 28th, offering another chance to spy the gas giant in the dawn sky, using the nearby crescent Moon as a guide.

The Moon and Jupiter in the daytime skies on Novemebr.
The Moon and Jupiter in the daytime skies on October 28th. Image credit: Stellarium.

And another interesting pairing is coming right up on the morning of Tuesday, October 11th, when Mercury passes just 0.8 degrees (48′) NNE of Jupiter. Both are only 12 degrees west of the Sun at closest approach, which occurs around 10:00 UT. Still, both will appear as an interesting pseudo-double star, with Mercury shining at magnitude -1.1 and Jupiter only half a magnitude fainter at -1.6.

You can even see Jupiter coming off of solar conjunction and headed toward dawn skies courtesy of SOHO’s LASCO C3 camera:

Jupiter (arrowed) exiting the 15 degree wide field of view of SOHO's LASCO C3 camera on October 5th. Image credit: NASA/ESA/SOHO.
Jupiter (arrowed) exiting the 15 degree wide field of view of SOHO’s LASCO C3 camera on October 5th. Image credit: NASA/ESA/SOHO.

Callisto, the outermost large moon of Jupiter, ceased casting its shadow on Jupiter earlier this year on September 1st 2016. Callisto is the only large moon that can ‘miss’ the gas giant’s cloud tops. Callisto must be involved for a triple shadow transit to occur, and the moon resumes regularly casting its shadow on Jove on December 4th, 2019.

Callisto can also experience total solar eclipses similar to those seen from the Earth during the mutual eclipse season for Jupiter’s moons, albeit shorter in duration:

And don ‘t forget: we’ve got a spacecraft currently exploring Jupiter for the next year and a half: NASA’s very own Juno.

Be sure to check out the Jovian action over the next month, gracing a dawn sky near you.

Posted on by Ken Kremer

NASA’s First SLS Mars Rocket Fuel Tank Completes Welding

Welding is complete on the largest piece of the core stage that will provide the fuel for the first flight of NASA's new rocket, the Space Launch System, with the Orion spacecraft in 2018. The core stage liquid hydrogen tank has completed welding on the Vertical Assembly Center at NASA's Michoud Assembly Facility in New Orleans. Credit: NASA/MAF/Steven Seipel
Welding is complete on the largest piece of the core stage that will provide the fuel for the first flight of NASA's new rocket, the Space Launch System, with the Orion spacecraft in 2018. The core stage liquid hydrogen tank has completed welding on the Vertical Assembly Center at NASA's Michoud Assembly Facility in New Orleans. Credit: NASA/MAF/Steven Seipel
Welding is complete on the largest piece of the core stage that will provide the fuel for the first flight of NASA’s new rocket, the Space Launch System, with the Orion spacecraft in 2018. The core stage liquid hydrogen tank has completed welding on the Vertical Assembly Center at NASA’s Michoud Assembly Facility in New Orleans. Credit: NASA/MAF/Steven Seipel

The first of the massive fuel tanks that will fly on the maiden launch of NASA’s SLS mega rocket in late 2018 has completed welding at the agency’s rocket manufacturing facility in New Orleans – marking a giant step forward for NASA’s goal of sending astronauts on a ‘Journey to Mars’ in the 2030s.

Technicians have just finished welding together the liquid hydrogen (LH2) fuel tank in the Vertical Assembly Center (VAC) welder at NASA’s Michoud Assembly Facility (MAF) in New Orleans. The VAC is the world’s largest welder.

Welding is nearly complete on the liquid hydrogen tank will provide the fuel for the first flight of NASA's new rocket, the Space Launch System, with the Orion spacecraft in 2018. The tank has now has now completed welding on the Vertical Assembly Center at NASA's Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com
Welding is nearly complete on the liquid hydrogen tank will provide the fuel for the first flight of NASA’s new rocket, the Space Launch System, with the Orion spacecraft in 2018. The tank has now has now completed welding on the Vertical Assembly Center at NASA’s Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com

This flight version of the hydrogen tank is the largest of the two fuel tanks making up the SLS core stage – the other being the liquid oxygen tank (LOX).

In fact the 130 foot tall hydrogen tank is the biggest cryogenic tank ever built for flight.

“Standing more than 130 feet tall, the liquid hydrogen tank is the largest cryogenic fuel tank for a rocket in the world,” according to NASA.

And it is truly huge – measuring also 27.6 feet (8.4 m) in diameter.

The liquid hydrogen tank qualification test article for NASA’s new Space Launch System (SLS) heavy lift rocket lies horizontally after final welding was completed at NASA’s Michoud Assembly Facility in New Orleans in July 2016. Credit: Ken Kremer/kenkremer.com
The liquid hydrogen tank qualification test article for NASA’s new Space Launch System (SLS) heavy lift rocket lies horizontally after final welding was completed at NASA’s Michoud Assembly Facility in New Orleans in July 2016. Credit: Ken Kremer/kenkremer.com

I recently visited MAF to see this giant tank when it was nearly finished welding in the VAC. I also saw the very first completed test tank version of the hydrogen tank, called the qualification tank which is virtually identical.

The precursor qualification tank was constructed to prove out all the manufacturing techniques and welding tools being utilized at Michoud.

The first liquid hydrogen tank, also called the qualification test article, for NASA's new Space Launch System (SLS) heavy lift rocket lies horizontally beside the Vertical Assembly Center robotic weld machine on July 22, 2016 after final welding was just completed at NASA’s Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com
The first liquid hydrogen tank, also called the qualification test article, for NASA’s new Space Launch System (SLS) heavy lift rocket lies horizontally beside the Vertical Assembly Center robotic weld machine on July 22, 2016 after final welding was just completed at NASA’s Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com

SLS is the most powerful booster the world has even seen and one day soon will propel NASA astronauts in the agency’s Orion crew capsule on exciting missions of exploration to deep space destinations including the Moon, Asteroids and Mars – venturing further out than humans ever have before!

NASA’s agency wide goal is to send humans to Mars by the 2030s with SLS and Orion.

The LH2 and LOX tanks sit on top of one another inside the SLS outer skin. Together the hold over 733,000 gallons of propellant.

The SLS core stage – or first stage – is mostly comprised of the liquid hydrogen and liquid oxygen cryogenic fuel storage tanks which store the rocket propellants at super chilled temperatures. Boeing is the prime contractor for the SLS core stage.

The SLS core stage stands some 212 feet tall.

The SLS core stage is comprised of five major structures: the forward skirt, the liquid oxygen tank (LOX), the intertank, the liquid hydrogen tank (LH2) and the engine section.

The LH2 and LOX tanks feed the cryogenic propellants into the first stage engine propulsion section which is powered by a quartet of RS-25 engines – modified space shuttle main engines (SSMEs) – and a pair of enhanced five segment solid rocket boosters (SRBs) also derived from the shuttles four segment boosters.

NASA engineers successfully conducted a development test of the RS-25 rocket engine Thursday, Aug. 18 at NASA’s Stennis Space Center near Bay St. Louis, Miss. The RS-25 will help power the core stage of the agency’s new Space Launch System (SLS) rocket for the journey to Mars. Credit: Ken Kremer/kenkremer.com
NASA engineers successfully conducted a development test of the RS-25 rocket engine Thursday, Aug. 18 at NASA’s Stennis Space Center near Bay St. Louis, Miss. The RS-25 will help power the core stage of the agency’s new Space Launch System (SLS) rocket for the journey to Mars. Credit: Ken Kremer/kenkremer.com

The vehicle’s four RS-25 engines will produce a total of 2 million pounds of thrust.

The tanks are assembled by joining previously manufactured dome, ring and barrel components together in the Vertical Assembly Center by a process known as friction stir welding. The rings connect and provide stiffness between the domes and barrels.

The LH2 tank is the largest major part of the SLS core stage. It holds 537,000 gallons of super chilled liquid hydrogen. It is comprised of 5 barrels, 2 domes, and 2 rings.

The LOX tank holds 196,000 pounds of liquid oxygen. It is assembled from 2 barrels, 2 domes, and 2 rings and measures over 50 feet long.

The maiden test flight of the SLS/Orion is targeted for no later than November 2018 and will be configured in its initial 70-metric-ton (77-ton) Block 1 configuration with a liftoff thrust of 8.4 million pounds – more powerful than NASA’s Saturn V moon landing rocket.

Although the SLS-1 flight in 2018 will be uncrewed, NASA plans to launch astronauts on the SLS-2/EM-2 mission slated for the 2021 to 2023 timeframe.

NASA’s Space Launch System (SLS) blasts off from launch pad 39B at the Kennedy Space Center in this artist rendering showing a view of the liftoff of the Block 1 70-metric-ton (77-ton) crew vehicle configuration. Credit: NASA/MSFC
NASA’s Space Launch System (SLS) blasts off from launch pad 39B at the Kennedy Space Center in this artist rendering showing a view of the liftoff of the Block 1 70-metric-ton (77-ton) crew vehicle configuration. Credit: NASA/MSFC

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

The newly assembled first liquid hydrogen tank, also called the qualification test article, for NASA's new Space Launch System (SLS) heavy lift rocket lies horizontally beside the Vertical Assembly Center robotic weld machine (blue) on July 22, 2016. It was lifted out of the welder (top) after final welding was just completed at NASA’s Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com
The newly assembled first liquid hydrogen tank, also called the qualification test article, for NASA’s new Space Launch System (SLS) heavy lift rocket lies horizontally beside the Vertical Assembly Center robotic weld machine (blue) on July 22, 2016. It was lifted out of the welder (top) after final welding was just completed at NASA’s Michoud Assembly Facility in New Orleans. Credit: Ken Kremer/kenkremer.com
Posted on by Evan Gough

Schiaparelli & The Problematic History Of Martian Landings

NASA's MSL Curiosity. NASA is the only agency to successfully place a lander on Mars. This self portrait shows Curiosity doing its thing on Mars. Image: NASA/JPL-Caltech/MSSS
NASA's MSL Curiosity. NASA is the only agency to successfully place a lander on Mars. This self portrait shows Curiosity doing its thing on Mars. Image: NASA/JPL-Caltech/MSSS

We may be living in the Golden Age of Mars Exploration. With multiple orbiters around Mars and two functioning rovers on the surface of the red planet, our knowledge of Mars is growing at an unprecedented rate. But it hasn’t always been this way. Getting a lander to Mars and safely onto the surface is a difficult challenge, and many landers sent to Mars have failed.

The joint ESA/Roscosmos Mars Express mission, and its Chiaparelli lander, is due at Mars in only 15 days. Now’s a good time to look at the challenges in getting a lander to Mars, and also to look back at the many failed attempts.

A model of the Schiaparelli lander. The lander is part of the ExoMars mission. By Pline - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26837226
A model of the Schiaparelli lander. The lander is part of the ExoMars mission. By Pline – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=26837226

For now, NASA has the bragging rights as the only organization to successfully land probes on Mars. And they’ve done it several times. But they weren’t the first ones to try. The Soviet Union tried first.

The USSR sent several probes to Mars starting back in the 1960s. They made their first attempt in 1962, but that mission failed to launch. That failure illustrates the first challenge in getting a craft to land on Mars: rocketry. We’re a lot better at rocketry than we were back in the 1960’s, but mishaps still happen.

Then in 1971, the Soviets sent a pair of probes to Mars called Mars 2 and Mars 3. They were both orbiters with detachable landers destined for the Martian surface. The fate of Mars 2 and Mars 3 provides other illustrative examples of the challenges in getting to Mars.

Mars 2 separated from its orbiter successfully, but crashed into the surface and was destroyed. The crash was likely caused by its angle of descent, which was too steep. This interrupted the descent sequence, which meant the parachute failed to deploy. So Mars 2 has the dubious distinction of being the first man-made object to reach Mars.

Mars 3 was exactly the same as Mars 2. The Soviets liked to do missions in pairs back then, for redundancy. Mars 3 separated from its orbiter and headed for the Martian surface, and through a combination of aerodynamic breaking, rockets, and parachutes, it became the first craft to make a soft landing on Mars. So it was a success, sort of.

A model of the Mars 3 lander with its petals open after landing. By NASA - http://nssdc.gsfc.nasa.gov/image/spacecraft/mars3_lander_vsm.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14634254
A model of the Mars 3 lander with its petals open after landing. By NASA – http://nssdc.gsfc.nasa.gov/image/spacecraft/mars3_lander_vsm.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=14634254

But after only 14.5 seconds of data transmission, it went quiet and was never heard from again. The cause was likely an intense dust storm. In an odd turn of events, NASA’s Mariner 9 orbiter reached Mars only days before Mars 2 and 3, becoming the first spacecraft to orbit another planet. It captured images of the planet-concealing dust storms, above which only the volcanic Olympus Mons could be seen. These images provided an explanation for the failure of Mars 3.

This image from the Mariner 9 orbiter shows Olympus Mons above the dust storms that concealed much of the planet when it arrived at Mars in 1971. Image: NASA
This image from the Mariner 9 orbiter shows Olympus Mons above the dust storms that concealed much of the planet when it arrived at Mars in 1971. Image: NASA

In 1973, the Soviets tried again. They sent four craft to Mars, two of which were landers, named Mars 6 and Mars 7. Mars 6 failed on impact, but Mars 7’s fate was perhaps a little more tragic. It missed Mars completely, by about 1300 km, and is in a helicentric orbit to this day. In our day and age, we just assume that our spacecraft will go where we want them to, but Mars 7 shows us that it can all go wrong. After all, Mars is a moving target.

In the 1970s, NASA was fresh off the success of their Apollo Program, and were setting their sites on Mars. They developed the Viking program which saw 2 landers, Viking 1 and Viking 2, sent to Mars. Both of them were probe/lander configurations, and both landers landed successfully on the surface of Mars. The Vikings sent back beautiful pictures of Mars that caused excitement around the world.

The Viking 2 lander captured this image of itself on the Martian surface. By NASA - NASA website; description,[1] high resolution image.[2], Public Domain, https://commons.wikimedia.org/w/index.php?curid=17624
The Viking 2 lander captured this image of itself on the Martian surface. By NASA – NASA website; description,[1] high resolution image.[2], Public Domain, https://commons.wikimedia.org/w/index.php?curid=17624

In 1997, NASA’s Martian Pathfinder made it to Mars and landed successfully. Pathfinder itself was stationary, but it brought a little rover called Sojourner with it. Sojourner explored the immediate landing area around Pathfinder. Sojourner became the first rover to operate on another planet.

Pathfinder was able to send back over 16,000 images of Mars, along with its scientific data. It was also a proof of concept mission for technologies such as automated obstacle avoidance and airbag mediated touchdown. Pathfinder helped lay the groundwork for the Mars Exploration Rover Mission. That means Spirit and Opportunity.

An artist's conception of Spirit/Opportunity working on Mars. By NASA/JPL/Cornell University, Maas Digital LLC - http://photojournal.jpl.nasa.gov/catalog/PIA04413 (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=565283
An artist’s conception of Spirit/Opportunity working on Mars. By NASA/JPL/Cornell University, Maas Digital LLC – http://photojournal.jpl.nasa.gov/catalog/PIA04413 (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=565283

But after Pathfinder, and before Spirit and Opportunity, came a time of failure for Martian landing attempts. Everybody took part in the failure, it seems, with Russia, Japan, the USA, and the European Space Agency all experiencing bitter failure. Rocket failures, engineering errors, and other terminal errors all contributed to the failure.

Japan’s Nozomi orbiter ran out of fuel before ever reaching Mars. NASA’s Mars Polar Lander failed its landing attempt. NASA’s Deep Space 2, part of the Polar Lander mission, failed its parachute-less landing and was never heard from. The ESA’s Beagle 2 lander made it to the surface, but two of its solar panels failed to deploy, ending its mission. Russian joined in the failure again, with its Phobos-Grunt mission, which was actually headed for the Martian moon Phobos, to retrieve a sample and send it back to Earth.

In one infamous failure, engineers mixed up the use of English units with Metric units, causing NASA’s Mars Climate Orbiter to burn up on entry. These failures show us that failure is not rare. It’s difficult and challenging to get to the surface of Mars.

After this period of failure, NASA’s Spirit and Opportunity rovers were both unprecedented successes. They landed on the Martian surface in January 2004. Both exceeded their planned mission length of three months, and Opportunity is still going strong now.

So where does that leave us now? NASA is the only one to have successfully landed a rover on Mars and have the rover complete its mission. But the ESA and Russia are determined to get there.

The Schiaparelli lander, as part of the ExoMars mission, is primarily a proof of technology mission. In fact, its full name is the Schiaparelli EDM lander, meaning Entry, Descent, and Landing Demonstrator Module.

It will have some small science capacity, but is really designed to demonstrate the ability to enter the Martian atmosphere, descend safely, and finally, to land on the surface. In fact, it has no solar panels or other power source, and will only carry enough battery power to survive for 2-8 days.

Schiaparelli faces the same challenges as other craft destined for Mars. Once launched successfully, which it was, it had to navigate its way to Mars. That took about 6 months, and since ExoMars is only 15 days away from arrival at Mars, it looks like it has successfully made its way their. But perhaps the trickiest part comes next: atmospheric entry.

Schiaparelli is like most Martian craft. It will make a ballistic entry into the Martian atmosphere, and this has to be done right. There is no room for error. The angle of entry is the key here. If the angle is too steep, Schiaparelli may overheat and burn up on entry. On the other hand, if the angle is too shallow, it could hit the atmosphere and bounce right back into space. There’ll be no second chance.

The entry and descent sequence is all pre-programmed. It will either work or it won’t. It would take way too long to send any commands to Schiaparelli when it is entering and descending to Mars.

If the entry is successful, the landing comes next. The exact landing location is imprecise, because of wind speed, turbulence, and other factors. Like other craft sent to Mars, Schiaparelli’s landing site is defined as an ellipse.

Schiaparelli will land somewhere in this defined ellipse on the surface of Mars. Image: IRSPS/TAS-I
Schiaparelli will land somewhere in this defined ellipse on the surface of Mars. Image: IRSPS/TAS-I

The lander will be travelling at over 21,000 km/h when it reaches Mars, and will have only 6 or 7 minutes to descend. At that speed, Schiaparelli will have to withstand extreme heating for 2 or 3 minutes. It’s heat shield will protect it, and will reach temperatures of several thousand degrees Celsius.

It will decelerate rapidly, and at about 10km altitude, it will have slowed to approximately 1700 km/h. At that point, a parachute will deploy, which will further slow the craft. After the parachute slows its descent, the heat shield will be jettisoned.

Schiaparelli's Descent and Landing Sequence. Image: ESA/ATG medialab
Schiaparelli’s Descent and Landing Sequence. Image: ESA/ATG medialab. Click here for larger image.

On Earth, a parachute would be enough to slow a descending craft. But with Mars’ less dense atmosphere, rockets are needed for the final descent. An onboard radar will monitor Schiaparelli’s altitude as it approaches the surface, and rockets will fire to slow it to a few meters per second in preparation for landing.

In the final moments, the rockets will stop firing, and a short free-fall will signal Schiaparelli’s arrival on Mars. If all goes according to plan, of course.

We won’t have much longer to wait. Soon we’ll know if the ESA and Russia will join NASA as the only agencies to successfully land a craft on Mars. Or, if they’ll add to the long list of failed attempts.

Posted on by Matt Williams

Was SpaceX’s Lost Falcon 9 The Victim Of Sabotage?

Rocket lifting from Space Launch Complex 40, located at Cape Canaveral Air Force Station in Florida. Credit: SpaceX

On Sept. 1st, 2016, aerospace giant SpaceX suffered a terrible setback when one of their Falcon 9 rockets inexplicably exploded during a fueling test. An investigation into the causes of the accident – which Musk described as being the “most difficult and complex failure” in the company’s history – was immediately mounted.

And while the focus of the investigation has been on potential mechanical failures – such as a possible breach In 2nd stage helium system – another line in inquiry also came to light recently. In this case, the focus was on the ongoing feud between SpaceX and its greatest competitor, United Launch Alliance (ULA), and whether or not that could have played a role.

Speculation about this possible connection began after three unnamed industry officials who were familiar with the accident shared details of an incident that happened a few weeks after the explosion. According to The Washington Post, these officials claimed that SpaceX had come across something suspicious during the course of their investigation.

On Sept. 1st, one of SpaceX's Falcon 9 rocket's exploded during a static firing test. The company is now facing a potential legal battle over the damage caused. Credit: SpaceX
On Sept. 1st, one of SpaceX’s Falcon 9 rocket’s exploded during a static firing test. The company is now facing a potential legal battle over the damage caused. Credit: SpaceX

After pouring over images and video from the explosion, SpaceX investigators noticed an odd shadow and then a white spot on the roof of building located close to their launch complex. The building is currently being leased by ULA to refurbish their Sensible Modular Autonomous Return Technology (SMART) rocket motors – a key component in the company’s new Vulcan rocket.

Located about one and half kilometers (1 mile) from SpaceX’s launch facilities, and has a clear line of sight on the launch pad. SpaceX dispatched an representative to check it out, who arrived at the building and requested access to the roof. A ULA representative denied them access and called Air Force investigators, who then inspected the roof themselves and determined that nothing of a suspicions nature was there.

While the incident proved to be inconclusive, it is the fact that it was not previously reported that is raising some eyebrows. And it is just another mysterious detail to come from an accident that remains largely unexplained. However, in all likelihood the incident was avoided to prevent embarrassment to either company, and to avoid fueling speculations about possible sabotage (which seems highly unlikely at this point).

In the meantime, SpaceX is still investigating the explosion with the help of NASA, the Federal Aviation Administration (FAA), the USAF’s 45th Space Wing. Musk commented on the ongoing investigation while attending the International Astronautical Congress in Guadalajara, Mexico.

Mangled SpaceX Falcon 9 strongback after prelaunch explosion destroyed the rocket and AMOS-6 payload and damaged the pad. Credit: Ken Kremer/kenkremer.com
Mangled SpaceX Falcon 9 strongback after prelaunch explosion destroyed the rocket and AMOS-6 payload and damaged the pad. Credit: Ken Kremer/kenkremer.com

In the midst of sharing the latest details of his vision to colonize Mars, Musk was quoted by The Washington Post as saying that the investigation is his company’s “absolute top priority.” As for the cause, he went on to say that they have “eliminated all of the obvious possibilities for what occurred there. So what remains are the less probable answers.”

Whether or not sabotage is a realistic possibility, this incident does serve to highlight the rivalry between SpaceX and ULA. Prior to 2014, ULA was the sole provider of launch services for the US Air Force, until a lawsuit from SpaceX compelled them to open the field to competition. Since then, both companies have been fighting – sometimes bitterly – to secure national security contracts.

It has also brought the issue of government oversight and accountability to the fore. On Sept. 29th, members of Congress Mike Coffman (R-Co) and Robert Aderholt (R-Al) sent a congressional letter to the heads of NASA, the US Air Force and the FAA expressing concerns about SpaceX’s recent accidents and the need for “assured access to space”.

In the letter, Coffman and Aderholt indicated that authority for investigating this and other accidents involving commercial space companies should be entrusted to the federal government:

“The investigative responses to both SpaceX failures raise serious concerns about the authority provided to commercial providers and the protection of national space assets. In both Falcon 9 explosions, NASA and the FAA granted primary responsibility for conducting the mishap investigation to SpaceX. Although subject to FAA oversight, it can be asserted the investigation lacked the openness taxpayers would expect before a return-to-flight.”

SpaceX Falcon 9 rocket explodes about 2 minutes after liftoff from Cape Canaveral Air Force Station in Florida on June 28, 2015. Credit: Ken Kremer/kenkremer.com
SpaceX Falcon 9 rocket explodes about 2 minutes after liftoff from Cape Canaveral Air Force Station in Florida on June 28, 2015. Credit: Ken Kremer/kenkremer.com

In other words, several Republican members of Congress hope to make SpaceX’s return to flight contingent on more stringent federal oversight. This may prove to be a source of inconvenience for SpaceX, which has stated that they intend to return to regular flights with their Falcon 9 rockets by November 1st.

Then again, increased federal oversight may also be beneficial in the long run. As is stated in the letter, both accidents involving SpaceX in the past few months occurred after the USAF signed off on the rockets involved:

“Both accidents occurred after the Air Force certified the Falcon 9 launch vehicle for U.S. national security launches, less than fifteen months ago. The certification, designed to subject the Falcon 9’s design and manufacturing process to a review of their technical and manufacturing rigor, appears to have fallen short of ensuring reliable assured US access to space for our most important payloads.”

Clearly, something is wrong if technical failures are not being caught in advance. But then again, space exploration is a hard business, and even the most routine checks can’t account for everything. Nevertheless, if there’s one thing that the Space Race taught us, it is that fierce competition can lead to mistakes, which can in turn cost lives.

As such, demanding that the federal authorities be on hand to ensure that safety standards are met, and that all competitors are being subjected to the same regulatory framework (without preference), might not be a bad idea.

Further Reading: The Washington Post

Posted on by Fraser Cain

What Happens When Black Holes Collide?

The sign of a truly great scientific theory is by the outcomes it predicts when you run experiments or perform observations. And one of the greatest theories ever proposed was the concept of Relativity, described by Albert Einstein in the beginning of the 20th century.

In addition to helping us understand that light is the ultimate speed limit of the Universe, Einstein described gravity itself as a warping of spacetime.

He did more than just provide a bunch of elaborate new explanations for the Universe, he proposed a series of tests that could be done to find out if his theories were correct.

One test, for example, completely explained why Mercury’s orbit didn’t match the predictions made by Newton. Other predictions could be tested with the scientific instruments of the day, like measuring time dilation with fast moving clocks.

Since gravity is actually a distortion of spacetime, Einstein predicted that massive objects moving through spacetime should generate ripples, like waves moving through the ocean.

The more massive the object, the more it distorts spacetime. Credit: LIGO/T. Pyle
The more massive the object, the more it distorts spacetime. Credit: LIGO/T. Pyle

Just by walking around, you leave a wake of gravitational waves that compress and expand space around you. However, these waves are incredibly tiny. Only the most energetic events in the entire Universe can produce waves we can detect.

It took over 100 years to finally be proven true, the direct detection of gravitational waves. In February, 2016, physicists with the Laser Interferometer Gravitational Wave Observatory, or LIGO announced the collision of two massive black holes more than a billion light-years away.

Any size of black hole can collide. Plain old stellar mass black holes or supermassive black holes. Same process, just on a completely different scale.

Colliding black holes. Credit: LIGO/A. Simonnet
Colliding black holes. Credit: LIGO/A. Simonnet

Let’s start with the stellar mass black holes. These, of course, form when a star with many times the mass of our Sun dies in a supernova. Just like regular stars, these massive stars can be in binary systems.

Imagine a stellar nebula where a pair of binary stars form. But unlike the Sun, each of these are monsters with many times the mass of the Sun, putting out thousands of times as much energy. The two stars will orbit one another for just a few million years, and then one will detonate as a supernova. Now you’ll have a massive star orbiting a black hole.  And then the second star explodes, and now you have two black holes orbiting around each other.

As the black holes zip around one another, they radiate gravitational waves which causes their orbit to decay. This is kind of mind-bending, actually. The black holes convert their momentum into gravitational waves.

As their angular momentum decreases, they spiral inward until they actually collide.  What should be one of the most energetic explosions in the known Universe is completely dark and silent, because nothing can escape a black hole. No radiation, no light, no particles, no screams, nothing. And if you mash two black holes together, you just get a more massive black hole.

The gravitational waves ripple out from this momentous collision like waves through the ocean, and it’s detectable across more than a billion light-years.

Arial view of LIGO Livingston. (Image credit: The LIGO Scientific Collaboration).
Arial view of LIGO Livingston. Credit: The LIGO Scientific Collaboration

This is exactly what happened earlier this year with the announcement from LIGO. This sensitive instrument detected the gravitational waves generated when two black holes with 30 solar masses collided about 1.3 billion light-years away.

This wasn’t a one-time event either, they detected another collision with two other stellar mass black holes.

Regular stellar mass black holes aren’t the only ones that can collide. Supermassive black holes can collide too.

From what we can tell, there’s a supermassive black hole at the heart of pretty much every galaxy in the Universe. The one in the Milky Way is more than 4.1 million times the mass of the Sun, and the one at the heart of Andromeda is thought to be 110 to 230 million times the mass of the Sun.

In a few billion years, the Milky Way and Andromeda are going to collide, and begin the process of merging together. Unless the Milky Way’s black hole gets kicked off into deep space, the two black holes are going to end up orbiting one another.

Just with the stellar mass black holes, they’re going to radiate away angular momentum in the form of gravitational waves, and spiral closer and closer together. Some point, in the distant future, the two black holes will merge into an even more supermassive black hole.

View of Milkdromeda from Earth "shortly" after the merger, around 3.85-3.9 billion years from now Credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger
View of Milkdromeda from Earth “shortly” after the merger, around 3.85-3.9 billion years from now. Credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger

The Milky Way and Andromeda will merge into Milkdromeda, and over the future billions of years, will continue to gather up new galaxies, extract their black holes and mashing them into the collective.

Black holes can absolutely collide. Einstein predicted the gravitational waves this would generate, and now LIGO has observed them for the first time. As better tools are developed, we should learn more and more about these extreme events.

Posted on by Nancy Atkinson

Odds Are Blue Origin Launch Test Will End In Fiery Destruction: Watch Live

New Shepard Pusher Escape System. Credit: Blue Origin.

The last time an in-flight escape system test for a crew capsule took place was during the Apollo program, in 1966. Now, you can watch live as Blue Origin tests the escape system for their New Shepard rocket on Wednesday, October 5, 2016 at 10:45 a.m. ET. The test was originally planned for today (Tuesday) but was postponed because of inclement weather.

You can watch live here:

As founder Jeff Bezos described the test, “Our next flight is going to be dramatic, no matter how it ends.” If all goes well, the crew capsule (empty, this time) should land rather gently. The likely end for the rocket booster, however, will be its destruction in a ball of flames.

Dramatic, indeed.

The New Shepard launching from its facility in West Texas. Image: Blue Origin
The New Shepard rocket launching from its facility in West Texas. Image: Blue Origin

Although the New Shepard has already launched successfully four times since November 2015, this fifth flight will test the system to protect future passengers from any anomaly during launch. Unlike the Apollo escape system that used an escape “tower” motor located on top of the capsule to ‘pull’ the crew cabin away from a failing booster, New Shepard’s escape system is mounted underneath the capsule, to ‘push’ the capsule away from a potentially exploding booster.

As the video below from Blue Origin explains, “Like the airbag in your car, this full envelope capsule escape system is always there if needed.” Bezos also described the test in an email:

About 45 seconds after liftoff at about 16,000 feet, we’ll intentionally command escape. Redundant separation systems will sever the crew capsule from the booster at the same time we ignite the escape motor. The escape motor will vector thrust to steer the capsule to the side, out of the booster’s path. The high acceleration portion of the escape lasts less than two seconds, but by then the capsule will be hundreds of feet away and diverging quickly. It will traverse twice through transonic velocities – the most difficult control region – during the acceleration burn and subsequent deceleration. The capsule will then coast, stabilized by reaction control thrusters, until it starts descending. Its three drogue parachutes will deploy near the top of its flight path, followed shortly thereafter by main parachutes.

While SpaceX successfully tested their escape system in May 2015, it wasn’t an in-flight test. The Crew Dragon spacecraft abort system was launched off a specially built platform at Cape Canaveral Air Force Station’s Space Launch Complex 40 in Florida. The engines fired for about six seconds, instantly producing about 15,000 pounds of thrust each and lifting the spacecraft out over the Atlantic Ocean and parachuting safely into the water.

Bezos said that while they’d really like to retire this New Shepard booster and put it in a museum, that’s probably not a possibility.

New Shepard comes in for a landing with drag brakes and landing gear deployed. Image: Blue Origin.
New Shepard comes in for a landing with drag brakes and landing gear deployed. Image: Blue Origin.

“It’s the first ever rocket booster to fly above the Karman line into space and then land vertically upon the Earth,” he said. “But the booster was never designed to survive an in-flight escape. The capsule escape motor will slam the booster with 70,000 pounds of off-axis force delivered by searing hot exhaust. The aerodynamic shape of the vehicle quickly changes from leading with the capsule to leading with the ring fin, and this all happens at maximum dynamic pressure.”

Monte Carlo simulations show there’s some chance the booster can survive those stresses and land vertically as it’s done previously. But probably not. There will still be propellant on board and if it lands hard, as expected, Bezos said “its impact with the desert floor will be most impressive.”

You can access the live feed on Blue Origin’s website.

Posted on by Matt Williams

When Will We Send Astronauts to Mars?

NASA astronauts exploring Mars on future missions starting perhaps in the 2030’s will require protection from long term exposure to the cancer causing space radiation environment. Credit: NASA.

History was made on July 20th, 1969, when Apollo 11 astronauts Neil Armstrong and Buzz Aldrin set foot on the surface of the Moon. The moment was the culmination of decades of hard work, research, development and sacrifice. And since that time, human beings have been waiting and wondering when we might achieve the next great astronomical milestone.

So really, when will we see a man or woman set foot on Mars? The prospect has been talked about for decades, back when NASA and the Soviets were still planning on setting foot on the Moon. It is the next logical step, after all. And at present, several plans are in development that could be coming to fruition in just a few decades time.

Original Proposals:

Werner Von Braun, the (in)famous former Nazi rocket scientist – and the man who helped spearhead NASA’s Project Mercury – was actually the first to develop a concept for a crewed mission to Mars. Titled The Mars Project (1952), his proposal called for ten spacecraft (7 passenger, 3 cargo) that would transport a crew of 70 astronauts to Mars.

In between launching V-2s in New Mexico and developing rockets at Redstone Arsenal, Von Braun had time to write Mars Projekt (1952) in which he outlined a mission to Mars delivering 70 explorers. Much has changed since that early vision but some of his concepts may still become a reality and solve the problem of sending SpaceX colonists to Mars. (Credit: Mars Project, Von Braun)
In between launching V-2s in New Mexico and developing rockets at Redstone Arsenal, Von Braun had time to write Mars Projekt (1952). Credit: Mars Project, Von Braun

His proposal was based in part on the large Antarctic expedition known as Operation Highjump (1946–1947), a US Navy program which took place a few years before he started penning his treatise. The plan called for the construction of the interplanetary spacecraft in around the Earth using a series of reusable space shuttles.

He also believed that, given the current pace of space exploration, such a mission could be mounted by 1965 (later revised to 1980) and would spend the next three years making the round trip mission. Once in Mars orbit, the crew would use telescopes to find a suitable site for their base camp near the equator.

A landing crew would then descend using a series of detachable winged aircraft (with ski landing struts) and glide down to land on the polar ice caps. A skeleton crew would remain with the ships in orbit as the surface crew would then travel 6,500 km overland using crawlers to the identified base camp site.

They would then build a landing strip which would allow the rest of the crew to descend from orbit in wheeled gliders. After spending a total of 443 days on Mars conducting surveys and research, the crew would use these same gliders as ascent craft to return to the mother ships.

Astronaut Eugene pollo 17 mission, 11 December 1972. Astronaut Eugene A. Cernan, commander, makes a short checkout of the Lunar Roving Vehicle (LRV)
Astronaut Eugene A. Cernan during the Apollo 17 mission, December 11th, 1972, shown conducting a checkout of the Lunar Roving Vehicle (LRV). Credit: NASA

Von Braun not only calculated the size and weight of each ship, but also how much fuel each would require for the round trip. He also computed the rocket burns necessary to perform the required maneuvers. Because of the detailed nature, calculations and planning in his proposal, The Mars Project remains one of the most influential books on human missions to the Red Planet.

Obviously, such a mission didn’t happen by 1965 (or 1980 for that matter). In fact, humans didn’t even return to the Moon after Eugene Cernan climbed out of the Apollo 17 capsule in 1972. With the winding down of the Space Race and the costs of sending astronauts to the Moon, plans to explore Mars were placed on the backburner until the last decade of the 20th century.

In 1990, a proposal called Mars Direct was developed by Robert Zubrin, founder of the Mars Society and fellow aerospace engineer David Baker. This plan envisioned a series of cost-effective mission to Mars using current technology, with the ultimate goal of colonization.

The initial missions would involve crews landing on the surface and leaving behind hab-structures, thus making subsequent missions easier to undertake. In time, the surface habs would give way to subsurface pressurized habitats built from locally-produced Martian brick. This would represent a first step in the development of in-situ resource utilization, and eventual human settlement.

Artist's rendering of Mars Semi-Direct/DRA 1.0: The Manned Habitat Unit is "docked" alongside a pre placed habitat that was sent ahead of the Earth Return Vehicle. Credit: NASA
Artist’s rendering Manned Habitat Units and Mars vehicles, part of the Mars Design Reference Mission 3.0. Credit: NASA

During and after this initial phase of habitat construction, hard-plastic radiation- and abrasion-resistant geodesic domes would be deployed to the surface for eventual habitation and crop growth. Local industries would begin to grow using indigenous resources, which would center around the manufacture of plastics, ceramics and glass out of Martian soil, sand and hydrocarbons.

While Zubrin acknowledged that Martian colonists would be partially Earth-dependent for centuries, he also stated that a Mars colony would also be able to create a viable economy. For one, Mars has large concentrations of precious metals that have not been subjected to millennia of human extracting. Second, the concentration of deuterium – a possible source for rocket fuel and nuclear fusion – is five times greater on Mars.

In 1993, NASA adopted a version of this plan for their “Mars Design Reference” mission, which went through five iterations between 1993 and 2009. And while it involved a great deal of thinking and planning, it failed to come up with any specific hardware or projects.

Current Proposals:

Things changed in the 21st century after two presidential administrations made fateful decisions regarding NASA. The first came in 2004 when President George W. Bush announced the “Vision for Space Exploration“. This involved retiring the Space Shuttle and developing a new class of launchers that could take humans back to the Moon by 2020 – known as the Constellation Program.

Then, in February of 2010, the Obama administration announced that it was cancelling the Constellation Program and passed the Authorization Act of 2010. Intrinsic to this plan was a Mars Direct mission concept, which called for the development of the necessary equipment and systems to mount a crewed mission to Mars by the 2030s.

In 2015, NASA’s Human Exploration and Operations Mission Directorate (HEOMD) presented the “Evolvable Mars Campaign”, which outlined their plans for their “Journey to Mars’ by the 2030s. Intrinsic to this plan was the use of the new Orion Multi-Purpose Crew Vehicle (MPCV) and the Space Launch System (SLS).

The proposed journey would involve Three Phases, which would involve a total of 32 SLS launches between 2018 and the 2030s. These missions would send all the necessary components to cis-lunar space and then onto near-Mars space before making crewed landings onto the surface.

Phase One (the “Earth Reliant Phase”) calls for long-term studies aboard the ISS until 2024, as well as testing the SLS and Orion Crew capsule. Currently, this involves the planned launch of Exploration Mission 1 (EM-1) in Sept. of 2018, which will be the first flight of the SLS and the second uncrewed test flight of the Orion spacecraft.

NASA's Journey to Mars. NASA is developing the capabilities needed to send humans to an asteroid by 2025 and Mars in the 2030s. Credit: NASA/JPL
NASA’s Journey to Mars. NASA is developing the capabilities needed to send humans to an asteroid by 2025 and Mars in the 2030s. Credit: NASA/JPL

NASA also plans to capture a near=Earth asteroid and bring it into lunar orbit, as a means of testing the capabilities and equipment for a Mars mission. Known as the Asteroid Redirect Mission, this mission is scheduled to take place in the 2020s and would primarily involve a robotic mission towing the asteroid and returning samples.

Exploration Mission 2 (EM-2), the first crewed flight using the Orion capsule, would conduct a flyby around the Moon and this asteroid between 2021 and 2023. At this point, NASA would be moving into Phase Two (“Proving Ground”) of the Journey to Mars, where the focus would move away from Earth and into cis-lunar space.

Multiple SLS launches would deliver the mission components during this time – including a habitat that would eventually be transported to Martian orbit, landing craft, and exploration vehicles for the surface of Mars. This phase also calls for the testing of key technologies, like Solar Electric Propulsion (aka. the ion engine).

By the early 2030s, Phase Three (“Earth Independent”) would begin. This calls for testing the entry, descent and landing techniques needed to get to the Martian surface, and the development of in-situ resource utilization. It also calls for the transferring of all mission components (and an exploration crew) to Martian orbit, from which the crews would eventually mount missions to designated “Exploration Zones” on the surface.

On Sept. 15th, 2016, the Senate Committee on Commerce, Science, and Transportation passed the NASA Transition Authorization Act of 2016, a measure designed to ensure short-term stability for the agency in the coming year.

The European Space Agency (ESA) has long-term plans to send humans to Mars, though they have yet to build a manned spacecraft. As part of the Aurora Program, this would involve a crewed mission to Mars in the 2030s using an Ariane M rocket. Other key points along that timeline include the ExoMars rover (2016-2020), a crewed mission to the Moon in 2024, and an automated mission to Mars in 2026.

Roscosmos, the Russian Federal Space Agency, is also planning a crewed mission to Mars, but doesn’t envision it happening until between 2040 and 2060. In the meantime, they have conducted simulations (called Mars-500), which wrapped up in Russia back in 2011. The Chinese space agency similarly has plans to mount a crewed mission to Mars between 2040 and 2060, but only after crewed missions to Mars take place.

In 2012, a group of Dutch entrepreneurs revealed plans for a crowdfunded campaign to establish a human Mars base, beginning in 2023. Known as MarsOne, the plan calls for a series of one-way missions to establish a permanent and expanding colony on Mars, which would be financed with the help of media participation.

Other details of the MarsOne plan include sending a telecom orbiter by 2018, a rover in 2020, and the base components and its settlers by 2023. The base would be powered by 3,000 square meters of solar panels and the SpaceX Falcon 9 Heavy rocket would be used to launch the hardware. The first crew of 4 astronauts would land on Mars in 2025; then, every two years, a new crew of 4 astronauts would arrive.

SpaceX and Tesla CEO Elon Musk has also announced plans to establish a colony on Mars in the coming decades. Intrinsic to this plan is the development of the Mars Colonial Transporter (MCT), a spaceflight system that would rely of reusable rocket engines, launch vehicles and space capsules to transport humans to Mars and return to Earth.

As of 2014, SpaceX has begun development of the large Raptor rocket engine for the Mars Colonial Transporter, and a successful test was announced in September of 2016. In January 2015, Musk said that he hoped to release details of the “completely new architecture” for the Mars transport system in late 2015.

In June 2016, Musk stated in the first unmanned flight of the MCT spacecraft would take place in 2022, followed by the first manned MCT Mars flight departing in 2024. In September 2016, during the 2016 International Astronautical Congress, Musk revealed further details of his plan, which included the design for an Interplanetary Transport System (ITS) – an upgraded version of the MCT.

According to Musk’s estimates, the ITS would cost $10 billion to develop and would be ready to ferry the first passengers to Mars as early as 2024. Each of the SpaceX vehicles would accommodate 100 passengers, with trips being made every 26 months (when Earth and Mars are closest). Musk also estimated that tickets would cost $500,000 per person, but would later drop to a third of that.

And while some people might have a hard time thinking of MarsOne’s volunteers or SpaceX’s passengers as astronauts, they would nevertheless be human beings setting foot on the Red Planet. And if they should make it there before any crewed missions by a federal space agency, are we really going to split hairs?

So the question remains, when will see people sent to Mars? The answer is, assuming all goes well, sometime in the next two decades. And while there are plenty who doubt the legitimacy of recent proposals, or the timetables they include, the fact that we are speaking about going to Mars a very real possibility shows just how far we’ve come since the Apollo era.

And does anyone need to be reminded that there were plenty of doubts during the “Race to the Moon” as well? At the time, there were plenty of people claiming the resources could be better spent elsewhere and those who doubted it could even be done. Once again, it seems that the late and great John F. Kennedy should have the last word on that:

“We choose to go to the Moon! … We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one we intend to win.”

We’ve written many articles about humans traveling to Mars. Here’s how new technology might slash the time to travel to Mars down to 39 days, and here’s an article about a team that did a simulated Mars mission.

If you’d like more information about humans traveling to Mars, check out the Mars Society’s homepage. And here’s a link to MarsDrive, and another group looking to send people to Mars.

We’ve also recorded several episodes of Astronomy Cast about missions to Mars. Listen here, Episode 94: Humans to Mars, Part 1

Sources:

Posted on by Matt Williams

What are CubeSats?

NanoRacks CubeSats photographed after deployment from the ISS by an Expedition 38 crew member. Credit: NASA

One of the defining characteristics of the modern era of space exploration is the open nature of it. In the past, space was a frontier that was accessible only to two federal space agencies – NASA and the Soviet space program. But thanks to the emergence of new technologies and cost-cutting measures, the private sector is now capable of providing their own launch services.

In addition, academic institutions and small countries are now capable of building their own satellites for the purposes of conducting atmospheric research, making observations of Earth, and testing new space technologies. It’s what is known as the CubeSat, a miniaturized satellite that is allowing for cost-effective space research.

Structure and Design:

Also known as nanosatellites, CubeSats are built to standard dimensions of 10 x 10 x 11 cm (1 U) and are shaped like cubes (hence the name). They are scalable, coming in versions that measure 1U, 2Us, 3Us, or 6Us on a side, and typically weigh less than 1.33 kg (3 lbs) per U. CubSats of 3Us or more are the largest, being composed of three units stacked lengthwise with a cylinder encasing them all.

A cubesat structure, 1U in size. Credit: Wikipedia Commons/Svobodat
A cubesat structure, 1U in size, without the outer skin. Credit: Wikipedia Commons/Svobodat

In recent years larger CubeSat platforms have been proposed, which include a 12U model (20 x 20 x 30 cm or 24 x 24 x 36 cm), that would extend the capabilities of CubeSats beyond academic research and testing new technologies, incorporating more complex science and national defense goals.

The main reason for miniaturizing satellites is to reduce the cost of deployment, and because they can be deployed in the excess capacity of a launch vehicle. This reduces the risks associated with missions where additional cargo has to be piggybacked to the launcher, and also allows for cargo changes on short notice.

They can also be made using commercial off-the-shelf (COTS) electronics components, which makes them comparably easy to create. Since CubeSats missions are often made to very Low Earth Orbits (LEO), and experience atmospheric reentry after just days or weeks, radiation can largely be ignored and standard consumer-grade electronics may be used.

CubeSats are built from four specific types of aluminum alloy to ensure that they have the same coefficient of thermal expansion as the launch vehicle. The satellites are also coated with a protective oxide layer along any surface that comes into contact with the launch vehicle to prevent them from being cold welded into place by extreme stress.

Components:

CubeSats often carry multiple on-board computers for the sake of carrying out research, as well providing for attitude control, thrusters, and communications. Typically, other on-board computers are included to ensure that the main computer is not overburdened by multiple data streams, but all other on-board computers must be capable of interfacing with it.

An example of a 3U cubesat - 3 1U cubes stacked. This cubesat size could function as the telescope of a two cubesat telescope system. It could be a simple 10 cm diameter optic system or use fancier folding optics to improve its resolving power. (Credit: LLNL)
An example of a 3U cubesat – 3 1U cubes stacked. This cubesat size could function as the telescope of a two cubesat telescope system. It could be a simple 10 cm diameter optic system or use fancier folding optics to improve its resolving power. Credit: LLNL

Typically, a primary computer is responsible for delegating tasks to other computers – such as attitude control, calculations for orbital maneuvers, and scheduling tasks. Still, the primary computer may be used for payload-related tasks, like image processing, data analysis, and data compression.

Miniaturized components provide attitude control, usually consisting of reaction wheels, magnetorquers, thrusters, star trackers, Sun and Earth sensors, angular rate sensors, and GPS receivers and antennas. Many of these systems are often used in combination in order to compensate for shortcomings, and to provide levels of redundancy.

Sun and star sensors are used to provide directional pointing, while sensing the Earth and its horizon is essential for conducting Earth and atmospheric studies. Sun sensors are also useful in ensuring that the CubsSat is able to maximize its access to solar energy, which is the primary means of powering a CubeSat – where solar panels are incorporated into the satellites outer casing.

Meanwhile, propulsion can come in a number of forms, all of which involve miniaturized thrusters providing small amounts of specific impulse. Satellites are also subject to radiative heating from the Sun, Earth, and reflected sunlight, not to mention the heat generated by their components.

Will cubesats develop a new technological branch of astronomy? Goddard engineers are taking the necessary steps to make cubesat sized telescopes a reality. (Credit: NASA, UniverseToday/TRR)
Will cubesats develop a new technological branch of astronomy? Goddard engineers are taking the necessary steps to make cubesat sized telescopes a reality. (Credit: NASA, UniverseToday/TRR)

As such, CubeSat’s also come with insulation layers and heaters to ensure that their components do not exceed their temperature ranges, and that excess heat can be dissipated. Temperature sensors are often included to monitor for dangerous temperature increases or drops.

For communications, CubeSat’s can rely on antennae that work in the VHF, UHF, or L-, S-, C- and X-bands. These are mostly limited to 2W of power due to the CubeSat’s small size and limited capacity. They can be helical, dipole, or monodirection monopole antennas, though more sophisticated models are being developed.

Propulsion:

CubeSats rely on many different methods of propulsion, which has in turn led to advancements in many technologies. The most common methods includes cold gas, chemical, electrical propulsion, and solar sails. A cold gas thruster relies on inert gas (like nitrogen) which is stored in a tank and released through a nozzle to generate thrust.

As propulsion methods go, it is the simplest and most useful system a CubeSat can use. It is also one of the safest too, since most cold gases are neither volatile nor corrosive. However, they have limited performance and cannot achieve high impulse maneuvers. Hence why they are generally used in attitude control systems, and not as main thrusters.

This prototype 13-kilowatt Hall thruster was tested at NASA's Glenn Research Center in Cleveland and will be used by industry to develop high-power solar electric propulsion into a flight-qualified system. Credits: NASA
Miniaturized ion engines are a method of choice for providing thrust control for CubeSats. Credits: NASA

Chemical propulsion systems rely on chemical reactions to produce high-pressure, high-temperature gas which is then directed through a nozzle to create thrust. They can be liquid, solid, or a hybrid, and usually come down to the combination of chemicals combined with a catalysts or an oxidizer. These thrusters are simple (and can therefore be miniaturized easily), have low power requirements, and are very reliable.

Electric propulsion relies on electrical energy to accelerate charged particles to high speeds – aka. Hall-effect thrusters, ion thrusters, pulsed plasma thrusters, etc. This method is beneficial since it combines high specific-impulse with high-efficiency, and the components can be easily miniaturized. A disadvantage is that they require additional power, which means either larger solar cells, larger batteries, and more complex power systems.

Solar sails are also used as a method for propulsion, which is beneficial because it requires no propellant. Solar sails can also be scaled to the CubSat’s own dimensions, and the satellite’s small mass results in the greater acceleration for a given solar sail’s area.

However, solar sails still need to be quite large compared to the satellite, which makes mechanical complexity an added source of potential failure. At this time, few CubeSats have employed a solar sail, but it remains an area of potential development since it is the only method that needs no propellant or involves hazardous materials.

The Planetary Society's LightSail-1 solar sailing spacecraft is scheduled to ride a SpaceX Falcon Heavy rocket to orbit in 2016 with its parent satellite, Prox-1. Credit: Josh Spradling/The Planetary Society.
The Planetary Society’s LightSail-1 is one of the few concepts where a CubeSat relied on a solar sail. Credit: Josh Spradling/The Planetary Society.

Because the thrusters are miniaturized, they create several technical challenges and limitations. For instance, thrust vectoring (i.e. gimbals) is impossible with smaller thrusters. As such, vectoring must instead be achieved by using multiple nozzles to thrust asymmetrically or using actuated components to change the center of mass relative to the CubeSat’s geometry.

History:

Beginning in 1999, California Polytechnic State University and Stanford University developed  the CubeSat specifications to help universities worldwide to perform space science and exploration. The term “CubeSat” was coined to denote nano-satellites that adhere to the standards described in the CubeSat design specifications.

These were laid out by aerospace engineering professor Jordi Puig-Suari and Bob Twiggs, from the Department of Aeronautics & Astronautics at Stanford University. It has since grown to become an international partnership of over 40 institutes that are developing nano-satellites containing scientific payloads.

Initially, despite their small size, academic institutions were limited in that they were forced to wait, sometimes years, for a launch opportunity. This was remedied to an extent by the development of the Poly-PicoSatellite Orbital Deployer (otherwise known as the P-POD), by California Polytechnic. P-PODs are mounted to a launch vehicle and carry CubeSats into orbit and deploy them once the proper signal is received from the launch vehicle.

The BisonSat is one example of a CubeSat mission launched by NASA’s CubeSat Launch Initiative on Oct. 8, 2015. The BisonSat is an Earth science mission that will demonstrate the acquisition of 100-meter or better resolution visible light imagery of Earth using passive magnetic stabilization from a CubeSat. The science data, 69-by-52 kilometer color images with a resolution of 43 meters per pixel, a few of which will be images of the Flathead Indian Reservation in northwest Montana, will be used primarily for engaging tribal college students and tribal communities in NASA’s mission. BisonSat is the first CubeSat designed, built, tested, and operated by tribal college students. Credits: Salish Kootenai College
The BisonSat is one example of a CubeSat mission launched by NASA’s CubeSat Launch Initiative on Oct. 8, 2015. Credits: Salish Kootenai College

The purpose of this, according to JordiPuig-Suari, was “to reduce the satellite development time to the time frame of a college student’s career and leverage launch opportunities with a large number of satellites.” In short, P-PODs ensure that many CubeSats can be launched at any given time.

Several companies have built CubeSats, including large-satellite-maker Boeing. However, the majority of development comes from academia, with a mixed record of successfully orbited CubeSats and failed missions. Since their inception, CubeSats have been used for countless applications.

For example, they have been used to deploy Automatic Identification Systems (AIS) to monitor marine vessels, deploy Earth remote sensors, to test the long term viability of space tethers, as well as conducting biological and radiological experiments.

Within the academic and scientific community, these results are shared and resources are made available by communicating directly with other developers and attending CubeSat workshops. In addition, the CubeSat program benefits private firms and governments by providing a low-cost way of flying payloads in space.

An artist's rendering of MarCO A and B during the descent of InSight. NASA/JPL-Caltech
An artist’s rendering of MarCO A and B during the descent of InSight. NASA/JPL-Caltech

In 2010, NASA created the “CubeSat Launch Initiative“, which aims to provide launch services for educational institutions and non-profit organizations so they can get their CubeSats into space. In 2015, NASA initiated its Cube Quest Challenge as part of their Centennial Challenges Programs.

With a prize purse of $5 million, this incentive-competition aimed to foster the creation of small satellites capable of operating beyond low Earth orbit – specifically in lunar orbit or deep space. At the end of the competition, up to three teams will be selected to launch their CubeSat design aboard the SLS-EM1 mission in 2018.

NASA’s InSight lander mission (scheduled to launch in 2018), will also include two CubeSats. These will conduct a flyby of Mars and provide additional relay communications to Earth during the lander’s entry and landing.

Designated Mars Cube One (MarCO), this experimental 6U-sized CubeSat will will be the first deep-space mission to rely on CubeSat technology. It will use a high-gain, flat-paneled X-band antenna to transmit data to NASA’s Mars Reconnaissance Orbiter (MRO) – which will then relay it to Earth.

Engineers for NASA's MarCO technology demonstration check out a full-scale mechanical mock-up of the small craft in development as part of NASA's next mission to Mars. Mechanical engineer Joel Steinkraus and systems engineer Farah Alibay are on the team at NASA's Jet Propulsion Laboratory. Image credit: NASA/JPL-Caltech
NASA engineers Joel Steinkraus and Farah Alibay demonstrate a full-scale mechanical mock-up of a MarCo CubeSat. Credit: NASA/JPL-Caltech

Making space systems smaller and more affordable is one of the hallmarks of the era of renewed space exploration. It’s also one of the main reasons the NewSpace industry has been growing by leaps and bounds in recent years. And with greater levels of participation, we are seeing greater returns when it comes to research, development and exploration.

We have written many articles about CubeSat for Universe Today. Here’s Planetary Society to Launch Three Separate Solar Sails, First Interplanetary CubeSats to Launch on NASA’s 2016 InSight Mars Lander, Making CubeSats do Astronomy, What Can You Do With a Cubesat?, These Cubesats Could Use Plasma Thrusters to Leave Our Solar System.

If you’d like more info on the CubeSat, check out CubeSat’s official homepage.

We’ve recorded an episode of Astronomy Cast all about the Space Shuttle. Listen here, Episode 127: The US Space Shuttle.

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