Is there a more complicated and sophisticated technological engineering project than a spacecraft? Maybe a particle accelerator or a fusion power project. But other than those two, the answer is probably no.
Spacecraft like the ESA’s JUICE don’t just pop out of the lab ready to go. Each spacecraft like JUICE is a singular design, and they require years—or even a decade or more—of work before they ever see a launch pad. With a scheduled launch date of 2022, JUICE is in the middle of all that work. Now its cameras are capturing images of Jupiter and its icy moons as part of its navigation calibration and fine-tuning.
When SpaceIL’s Beresheet lander crashed into the Moon, it was a bitter-sweet moment for Israel’s space exploration aspirations. The privately-built spacecraft was punching above its weight class by proceeding on its journey to the Moon. Unfortunately, it crashed, ending the dream.
But Beresheet carried some unusual passengers, as part of an unusual, yet visionary, sub-mission: tardigrades.
Jezero crater is the landing spot for NASA’s upcoming 2020 rover. The crater is a rich geological site, and the 45 km wide (28 mile) impact crater contains at least five different types of rock that the rover will sample. Some of the landform features in the crater are 3.6 billion years old, making the site an ideal place to look for signs of ancient habitability.
Back in Ye Olden Times, the job of astronomer was a pretty exclusive club. Either you needed to be so rich and so bored that you could design, build, and operate your own private observatory, or you needed to have a rich and bored friend who could finance your cosmic curiosity for you. By contrast, today’s modern observatories are much more democratic, offering of a wealth of juicy scientific info for researchers across the globe. But that ease of access comes with its own price: you don’t get the instrument all to yourself, and that’s a challenge for young scientists and their research.
When Elon Musk of SpaceX tweets something interesting, it generates a wave of excitement. So when he tweeted recently that SpaceX might be working on a way to retrieve upper stages of their rockets, it set off a chain of intrigued responses.
SpaceX will try to bring rocket upper stage back from orbital velocity using a giant party balloon
SpaceX has been retrieving and reusing their lower stages for some time now, and it’s lowered the cost of launching payloads into space. But this is the first hint that they may try to do the same with upper stages.
Twitter responders wanted to know exactly what SpaceX has in mind, and what a “giant party balloon” might be. Musk hasn’t elaborated yet, but one of his Twitter followers had something interesting to add.
If you're proposing what I think you are, an ultra low ballistic entry coefficient decelerator, then you and @SpaceX should come see what we have at the @UofMaryland . We've been working on this for awhile and just finished some testing pic.twitter.com/nJBvyUnzaK
Universe Today contacted Mr. Kupec to see if he could help us understand what Musk may have been getting at. But first, a little background.
An “ultra low ballistic entry coefficient decelerator” is a bit of a mouthful. The ballistic coefficient measures how well a vehicle can overcome air resistance in flight. A high ballistic coefficient means a re-entry vehicle would not lose velocity quickly, and would reach Earth at high speeds. An ultra low ballistic entry coefficient decelerator would lose speed quickly, meaning that a vehicle would be travelling at low, subsonic speeds before reaching the ground.
To recover an upper stage booster, low speeds are desirable, since they generate less heat. But according to Kupec, there’s another problem that must be overcome.
“What happens when these things slow down to landing velocities? If your center of gravity is offset significantly behind your center of drag, as would be the case with a returning upper stage, it can get unstable. If the center of gravity of the re-entry vehicle is too high, it can become inverted, which is obviously not desirable.”
So the trick is to lower the speed of the re-entry vehicle to the point where the heat generated by reentry isn’t damaging the booster, and to do it without causing the vehicle to invert or otherwise become unstable. This isn’t a problem for the main stage boosters that SpaceX now routinely recovers; they have their own retro-rockets to guide their descent and landing. But for the upper stage boosters, which reach orbital velocities, it’s an obstacle that has to be overcome.
“My research is specifically focused on how high you can push the center of gravity and still maintain the proper flight configuration,” said Kupec.
But what about the “giant party balloon” that Musk tweeted about?
Musk could be referring, in colorful terms, to what’s called a ballute. The word is a combination of the words balloon and parachute. They were invented in the 1950’s by Goodyear Aerospace. They can arrest the descent of entry vehicles and provide stability during the descent.
“…the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric…” – Professor Dave Akin, University of Maryland
Universe Today contacted Professor Dave Akin of the University of Maryland for some insight into Musk’s tweet. Professor Akin has been working on reentry systems for over 2 decades.
In an e-mail exchange, Professor Akin told us, “There have been concepts proposed for deploying a large balloon on a cable that is towed behind you on entry. The balloon lowers your ballistic coefficient, which means you decelerate higher in the atmosphere and the heat load is less.” So the key is to scrub your speed before you get closer to Earth, where the atmosphere is thicker and generates more heat.
But according to Professor Akin, this won’t necessarily be easy to do. “To get the two orders of magnitude reduction in ballistic coefficient that Elon has been talking about the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric, so it’s not going to be all that easy.”
But Musk’s track record shows he doesn’t shy away from things that aren’t easy.
Retrieving upper rocket stages isn’t all about lowering launch costs, it’s also about space junk. The European Space Agency estimates that there are over 29,000 pieces of space junk orbiting Earth, and some of that junk is spent upper stage boosters. There have been some collisions and accidents already, with some satellites being pushed into different orbits. In 2009, the Iridium 33 communications satellite and the defunct Russian Cosmos 2251 communications satellite collided with each other, destroying both. If SpaceX can develop a way to retrieve its upper stage boosters, that means less space junk, and fewer potential collisions.
There’s a clear precedent for using balloons to manage reentry. With people like Professor Akin and Quinn Kupec working on it, SpaceX won’t have to reinvent the wheel. But they’ll still have a lot of work to do.
Musk tweeted one other thing shortly after his “giant party balloon” tweet:
The microgravity in space causes a number of problems for astronauts, including bone density loss and muscle atrophy. But there’s another problem: weightlessness allows astronauts’ spines to expand, making them taller. The height gain is permanent while they’re in space, and causes back pain.
A new SkinSuit being tested in a study at King’s College in London may bring some relief. The study has not been published yet.
The constant 24 hour microgravity that astronauts live with in space is different from the natural 24 hour cycle that humans go through on Earth. Down here, the spine goes through a natural cycle associated with sleep.
Sleeping in a supine position allows the discs in the spine to expand with fluid. When we wake up in the morning, we’re at our tallest. As we go about our day, gravity compresses the spinal discs and we lose about 1.5 cm (0.6 inches) in height. Then we sleep again, and the spine expands again. But in space, astronauts spines have been known to grow up to 7 cm. (2.75 in.)
Study leader David A. Green explains it: “On Earth your spine is compressed by gravity as you’re on your feet, then you go to bed at night and your spine unloads – it’s a normal cyclic process.”
In microgravity, the spine of an astronaut is never compressed by gravity, and stays unloaded. The resulting expansion causes pain. As Green says, “In space there’s no gravitational loading. Thus the discs in your spine may continue to swell, the natural curves of the spine may be reduced and the supporting ligaments and muscles — no longer required to resist gravity – may become loose and weak.”
The SkinSuit being developed by the Space Medicine Office of ESA’s European Astronaut Centre and the King’s College in London is based on work done by the Massachusetts Institute of Technology (MIT). It’s a spandex-based garment that simulates gravity by squeezing the body from the shoulders to the feet.
The Skinsuits were tested on-board the International Space Station by ESA astronauts Andreas Mogensen and Thomas Pesquet. But they could only be worn for a short period of time. “The first concepts were really uncomfortable, providing some 80% equivalent gravity loading, and so could only be worn for a couple of hours,” said researcher Philip Carvil.
Back on Earth, the researchers worked on the suit to improve it. They used a waterbed half-filled with water rich in magnesium salts. This re-created the microgravity that astronauts face in space. The researchers were inspired by the Dead Sea, where the high salt content allows swimmers to float on the surface.
“During our longer trials we’ve seen similar increases in stature to those experienced in orbit, which suggests it is a valid representation of microgravity in terms of the effects on the spine,” explains researcher Philip Carvil.
Studies using students as test subjects have helped with the development of the SkinSuit. After lying on the microgravity-simulating waterbed both with and without the SkinSuit, subjects were scanned with MRI’s to test the SkinSuit’s effectiveness. The suit has gone through several design revisions to make it more comfortable, wearable, and effective. It’s now up to the Mark VI design.
“The Mark VI Skinsuit is extremely comfortable, to the point where it can be worn unobtrusively for long periods of normal activity or while sleeping,” say Carvil. “The Mk VI provides around 20% loading – slightly more than lunar gravity, which is enough to bring back forces similar to those that the spine is used to having.”
“The results have yet to be published, but it does look like the Mk VI Skinsuit is effective in mitigating spine lengthening,” says Philip. “In addition we’re learning more about the fundamental physiological processes involved, and the importance of reloading the spine for everyone.”
ESA scientists have found one additional image from the Rosetta spacecraft hiding in the telemetry. This new image was found in the last bits of data sent by Rosetta immediately before it shut down on the surface of Comet 67P/Churyumov–Gerasimenko last year.
Planetary astronomer Andy Rivkin noted on Twitter that for size context, he estimates the block just right of center looks to be about the size of a hat. That’s a fun comparison to have (not to mention thinking about hats on Comet 67P!)
The picture has a scale of 2 mm/pixel and measures about 1 m across. It’s a really ‘close’ close-up of Comet 67P.
“The last complete image transmitted from Rosetta was the final one that we saw arriving back on Earth in one piece moments before the touchdown at Sais,” said Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany. “Later, we found a few telemetry packets on our server and thought, wow, that could be another image.”
The team explains that the image data were put into telemetry ‘packets’ aboard Rosetta before they were transmitted to Earth, and the final images were split into six packets. However, for the very last image, the transmission was interrupted after only three full packets. The incomplete data was not recognized as an image by the automatic processing software, but later, the engineers in Göttingen could make sense of these data fragments to reconstruct the image.
You’ll notice it is rather blurry. The OSIRIS camera team says this image only has about 53% of the full data and “therefore represents an image with an effective compression ratio of 1:38 compared to the anticipated compression ratio of 1:20, meaning some of the finer detail was lost.”
That is, it gets a lot blurrier as you zoom in compared with a full-quality image. They compared it to compressing an image to send via email, versus an uncompressed version that you would print out and hang on your wall.
Rosetta’s final resting spot is in a region of active pits in the Ma’at region on the two-lobed, duck-shaped comet.
Launched in 2004, Rosetta traveled nearly 8 billion kilometers and its journey included three Earth flybys and one at Mars, and two asteroid encounters. It arrived at the comet in August 2014 after being in hibernation for 31 months.
After becoming the first spacecraft to orbit a comet, it deployed the Philae lander in November 2014. Philae sent back data for a few days before succumbing to a power loss after it unfortunately landed in a crevice and its solar panels couldn’t receive sunlight.
But Rosetta showed us unprecedented views of Comet 67P and monitored the comet’s evolution as it made its closest approach and then moved away from the Sun. However, Rosetta and the comet moved too far away from the Sun for the spacecraft to receive enough power to continue operations, so the mission plan was to set the spacecraft down on the comet’s surface.
And scientists have continued to sift through the data, and this new image was found. Who knows what else they’ll find, hiding the data?
The more that planetary astronomers study asteroids, they more they’re realizing just how varied and different they can be. Some, like 16 Psyche are made of solid nickel and iron, while others are made of rock. Some asteroids have been found with moons, rings, and some icy objects really blur the line between comet and asteroid. In order to truly understand their nature, it would take dozens or maybe hundreds of individual missions on the scale of Rosetta or New Horizons.
Or maybe not.
A team of researchers with the Finnish Meteorological Institute announced today that the best way to explore the varied objects in the asteroid belt would be with a fleet of tiny nanosatellites – 50 ought to do the trick to explore 300 separate asteroids, bringing the individual costs down to a few hundred thousand dollars per asteroid. During a presentation they made at the European Planetary Science Congress (EPSC) 2017 in Riga on Tuesday, the researchers showed how these tiny satellites could travel out to the asteroid belt, gather data on individual asteroids, and return to Earth to download their data.
The 50 satellites could be launched together in a single vehicle, and then separate once in space, or they could fill extra space in existing launches. The exact launch orbit doesn’t matter, as long as the spacecraft can get outside the Earth’s protective magnetosphere, where they can catch a ride on the solar wind.
Once in space, 5-kg spacecraft would deploy a 20 km-long wire tether that would catch the solar wind; the constantly flowing particles coming off the Sun, imparting a tiny thrust. This is known as an “E-sail” or electric sail. Unlike a solar sail, which depends on the momentum of photons coming from the Sun, electric sails harvest the momentum of charged protons.
Researchers are still figuring out if this is an effective propulsion system for spacecraft. An Estonian prototype satellite was launched back in 2015, but its onboard motor failed to reel out its tether. The Finnish Aalto-1 satellite launched in June, 2017, and will test out a prototype electric sail in addition to several other experiments over the course of the next year. Even more advanced versions have been proposed, such as Heliopause Electrostatic Rapid Transit System (or HERTS), a mission which could reach 100 astronomical units in 10-15 years by deploying a huge electrified net in space.
In the case of this asteroid mission, each satellite’s electric sail would only give it a change in velocity of only one millimeter per second, but over the course of a 3.2 year mission, it would allow the spacecraft to reach the asteroid belt and return to Earth.
In fact, the spacecraft would use their tethers to maneuver within the asteroid belt, flying past as many targets as they can with this minuscule thrust. Each satellite should be able to reach at least 6-7 numbers asteroids, and maybe even more smaller ones.
Each satellite would be equipped with a telescope with only a 40 mm aperture. That’s the size of a small spotting scope or half a pair of binoculars, but it would be enough to resolve features on the surface of an asteroid as large as 100 meters across from 1,000 km away. In addition to taking visual images of the asteroid targets, the spacecraft would be equipped with an infrared spectrometer to determine its meteorology.
Because the spacecraft are so small, they won’t be capable of carrying a transmitter to send their data back to Earth. Instead, they’d store all their scientific findings on a memory card, and then dump their data when their orbit brings them back close to Earth.
The researchers estimate that development of the mission would probably cost about 60 million Euros, or $70 million dollars, bringing the cost per asteroid down to about 200,000 Euros or $240,000.
During its long mission to Saturn, the Cassini spacecraft has given us image after spectacular image of Saturn, its rings, and Saturn’s moons. The images of Saturn’s moon Enceladus are of particular interest when it comes to the search for life.
At first glance, Enceladus appears similar to other icy moons in our Solar System. But Cassini has shown us that Enceladus could be a cradle for extra-terrestrial life.
Our search for life in the Solar System is centred on the presence of liquid water. Maybe we don’t know for sure if liquid H2O is required for life. But the Solar System is huge, and the effort required to explore it is immense. So starting our search for life with the search for liquid water is wise. And in the search for liquid water, Enceladus is a tantalizing target.
Though Enceladus looks every bit like a frozen, lifeless world on its surface, it’s what lies beneath its frigid crust that is exciting. Enceladus appears to have a subsurface ocean, at least in it’s south polar region. And that ocean may be up to 10 km. deep.
Before we dive into that, (sorry), here are a few basic facts about Enceladus:
Enceladus is Saturn’s sixth largest moon
Enceladus is about 500 km in diameter (Earth’s Moon is 3,474 km in diameter)
Enceladus was discovered in 1789 by William Herschel
Enceladus is one of the most reflective objects in our Solar System, due to its icy surface
In 2005, Cassini first spied plumes of frozen water vapor erupting from the southern polar region. Called cryovolcanoes, subsequent study of them determined that they are the likely source of Saturn’s E Ring. The existence of these plumes led scientists to suspect that their source was a sub-surface ocean under Enceladus’ ice crust.
Finding plumes of water erupting from a moon is one thing, but it’s not just water. It’s salt water. Further study showed that the plumes also contained simple organic compounds. This advanced the idea that Enceladus could harbor life.
The geysers aren’t the only evidence for a sub-surface ocean on Enceladus. The southern polar region has a smooth surface, unlike the rest of the moon which is marked with craters. Something must have smoothed that surface, since it is next to impossible that the south polar region would be free from impact craters.
In 2005, Cassini detected a warm region in the south, much warmer than could be caused by solar radiation. The only conclusion is that Enceladus has a source of internal heating. That internal heat would create enough geologic activity to erase impact craters.
So now, two conditions for the existence of life have been met: liquid water, and heat.
The source of the heat on Enceladus was the next question facing scientists. That question is far from settled, and there could be several sources of heat operating together. Among all the possible sources for the heat, two are most intriguing when it comes to the search for life: tidal heating, and radioactive heating.
Tidal heating is a result of rotational and orbital forces. In Enceladus’ case, these forces cause friction which is dissipated as heat. This heat keeps the sub-surface ocean in liquid form, but doesn’t prevent the surface from freezing solid.
Radioactive heating is caused by the decay of radioactive isotopes. If Enceladus started out as a rocky body, and if it contained enough short-lived isotopes, then an enormous amount of heat would be produced for several million years. That action would create a rocky core surrounded by ice.
Then, if enough long-lived radioactive isotopes were present, they would continue producing heat for a much longer period of time. However, radioactive heating isn’t enough on its own. There would have to be tidal heating also.
More evidence for a large, sub-surface ocean came in 2014. Cassini and the Deep Space Network provided gravitometric measurements showing that the ocean is there. Those measurements showed that there is likely a regional, if not global, ocean some 10 km thick. Measurements also showed that the ocean is under an ice layer 30 to 40 km thick.
The discovery of a warm, salty ocean containing organic molecules is very intriguing, and has expanded our idea of what the habitable zone might be in our Solar System, and in others. Enceladus is much too distant from the Sun to rely on solar energy to sustain life. If moons can provide their own heat through tidal heating or radioactive heating, then the habitable zone in any solar system wouldn’t be determined by proximity to the star or stars at the centre.
Cassini’s mission is nearing its end, and it won’t fly by Enceladus again. It’s told us all it can about Enceladus. It’s up to future missions to expand our understanding of Enceladus.
Numerous missions have been talked about, including two that suggest flying through the plumes and sampling them. One proposal has a sample of the plumes being returned to Earth for study. Landing on Enceladus and somehow drilling through the ice remains a far-off idea better left to science fiction, at least for now.
Whether or not Enceladus can or does harbor life is a question that won’t be answered for a long time. In fact, not all scientists agree that there is a liquid ocean there at all. But whether it does or doesn’t harbor life, Cassini has allowed us to enjoy the tantalizing beauty of that distant object.
The incredible HiRISE camera on board the Mars Reconnaissance Orbiter turned its eyes away from its usual target – Mars’ surface – and for calibration purposes only, took some amazing images of Earth and our Moon. Combined to create one image, this is a marvelous view of our home from about 127 million miles (205 million kilometers) away.
Alfred McEwen, principal investigator for HiRISE said the image is constructed from the best photo of Earth and the best photo of the Moon from four sets of images. Interestingly, this combined view retains the correct positions and sizes of the two bodies relative to each other. However, Earth and the Moon appear closer than they actually are in this image because the observation was planned for a time at which the Moon was almost directly behind Earth, from Mars’ point of view, to see the Earth-facing side of the Moon.
“Each is separately processed prior to combining (in correct relative positions and sizes), so that the Moon is bright enough to see,” McEwen wrote on the HiRISE website. “The Moon is much darker than Earth and would barely show up at all if shown at the same brightness scale as Earth. Because of this brightness difference, the Earth images are saturated in the best Moon images, and the Moon is very faint in the best (unsaturated) Earth image.”
Earth looks reddish because the HiRISE imaging team used color filters similar to the Landsat images where vegetation appears red.
“The image color bandpasses are infrared, red, and blue-green, displayed as red, green, and blue, respectively,” McEwen explained. “The reddish blob in the middle of the Earth image is Australia, with southeast Asia forming the reddish area (vegetation) near the top; Antarctica is the bright blob at bottom-left. Other bright areas are clouds. We see the western near-side of the Moon.”
HiRISE took these pictures on Nov. 20, 2016, and this is not the first time HiRISE has turned its eyes towards Earth.
Back in 2007, HiRISE took this image, below, from Mars’ orbit when it was just 88 million miles (142 million km) from Earth. This one is more like how future astronauts might see Earth and the Moon through a telescope from Mars’ orbit.
If you look closely, you can make out a few features on our planet. The west coast outline of South America is at lower right on Earth, although the clouds are the dominant features. In fact, the clouds were so bright, compared with the Moon, that they almost completely saturated the filters on the HiRISE camera. The people working on HiRISE say this image required a fair amount of processing to make such a nice-looking picture.
You can see an image from a previous Mars’ orbiter, the Mars Global Surveyor, that took a picture of Earth, the Moon and Jupiter — all in one shot — back in 2003 here.