In a recent study submitted to Earth and Planetary Astrophysics, an international team of researchers discuss the various mission design options for reaching a hypothetical Planet 9, also known as “Planet X”, which state-of-the-art models currently estimate to possess a semi-major axis of approximately 400 astronomical units (AU). The researchers postulate that sending a spacecraft to Planet 9 could pose scientific benefits much like when NASA’s New Horizons spacecraft visited Pluto in 2015. But does Planet 9 actually exist?
Mining asteroids might be necessary for humanity to expand into the Solar System. But what effect would asteroid mining have on the world's economy? Credit: ESA.
Humanity seems destined to expand into the Solar System. What exactly that looks like, and how difficult and tumultuous the endeavour might be, is wide open to speculation. But there are some undeniable facts attached to the prospect.
We need materials to build infrastructure, and getting it all into space from Earth is not realistic. (Be quiet, space elevator people.)
New research suggests that Mercury is still contracting and shrinking. Credits: NASA/JHUAPL/Carnegie Institution of Washington/USGS/Arizona State University
BepiColombo made a quick visit to Venus in August and is on to its next rendezvous. On October 1st it’ll perform a flyby of Mercury, the spacecraft’s eventual destination. This visit is just a little flirtation—one of six—ahead of its eventual orbital link-up with Mercury in late 2025.
The quick visit will yield some scientific results, though, and they’ll be just a taste of what’s ahead in BepiColumbo’s one-year mission to Mercury.
An artist's illustration of the NEO Surveyor, a space telescope designed to detect and catalogue NEOs. Image Credit: NASA/JPL
A lot of the threats humanity faces come from ourselves. If we were listing them, we’d include tribalism, greed, and the fact that we’re evolved primates, and our brains have a lot in common with animal brains. Our animalistic brains subject us to many of the same destructive emotions and impulses that animals are subject to. We wage war and become embroiled in intergenerational conflicts. There are genocides, pogroms, doomed boatloads of migrants, and horrible mashups of all three.
Isn’t humanity fun?
But not all of the threats we face are as intractable as our internal ones. Some threats are external, and we can leverage our technologies and our knowledge of nature in the struggle against them. Case in point: asteroids.
First image of the star chosen as target for CHEOPS after cover opening. The star, at the centre of the image, is located at a distance of 150 light-years from us, in the constellation of Cancer. Image Credit:ESA/Airbus/CHEOPS Mission Consortium
The CHEOPS spacecraft is taking the first tentative steps in its mission. Back on January 29th, the spacecraft opened the cover on its lens. Now, we have the first images from CHEOPS.
Artist's impression of the Voyager 2 space probe. Credit: NASA
NASA’s Voyager 2 spacecraft went into fault protection mode on Tuesday January 28th. The fault protection routines automatically protect the spacecraft in harmful conditions. Both Voyagers have these routines programmed into their systems.
After it happened, NASA engineers were still in communication with the spacecraft and receiving telemetry.
The CHEOPS (CHaracterising ExOPlanets Satellite) spacecraft just opened the cover on its telescope. The spacecraft was launched on December 18th 2019 and has so far performed flawlessly. In one or two weeks we could get our first images from the instrument.
This scanning electron micrograph shows the crater left by the impact of a 10-micrometer particle traveling at more than 1 kilometer per second. Impacts at that speed produce some melting and erosion of the surface, as revealed by this research. Credit: MIT/Hassani-Gangaraj et al.
If there’s one thing that decades of operating in Low Earth Orbit (LEO) has taught us, it is that space is full of hazards. In addition to solar flares and cosmic radiation, one of the greatest dangers comes from space debris. While the largest bits of junk (which measure more than 10 cm in diameter) are certainly a threat, the real concern is the more than 166 million objects that range in size from 1 mm to 1 cm in diameter.
While tiny, these bits of junk can reach speeds of up to 56,000 km/h (34,800 mph) and are impossible to track using current methods. Because of their speed, what happens at the moment of impact has never been clearly understood. However, a research team from MIT recently conducted the first detailed high-speed imaging and analysis of the microparticle impact process, which will come in handy when developing space debris mitigation strategies. Continue reading “Micrometeorite Damage Under the Microscope”
Within the realm of physics, there are certain barriers that human beings have come to recognize. The most well-known is the speed of light, the maximum speed at which all conventional matter and all forms of information in the Universe can travel. This is a barrier that humanity may never be able to push past, mainly because doing so violate one of the most fundamental laws of physics – Einstein’s Theory of General Relativity.
But what about the speed of sound? This is another barrier in physics, but one which humanity has been able to break (several times over in fact). And when it comes to breaking this barrier, scientists use what is known as a Mach Number to represent the flow boundary past the local speed of sound. In other words, pushing past the sound barrier is defined as Mach 1. So how fast do you have to be going to do that?
Definition:
When we hear the term Mach 1 it is easy to assume it is the speed of sound through Earth’s atmosphere. However this term is more loaded than you might think. The truth is that a Mach Number is a ratio rather than an actual direct measurement of speed. And this ratio is due to the fact that the speed of sound varies from one location to the next, owing to differences in temperature and air density.
An F-22 Raptor reaching a velocity high enough to achieve a sonic boom. Credit: strangesounds.org
Mathematically, this can be defined as M = u/c, where M is the Mach number, u is the local flow velocity with respect to the boundaries (i.e. the speed of the object moving through the medium), and c is the speed of sound in that particular medium (i.e. local atmosphere, water, etc).
When the speed of sound is broken, this results in what is known as a “sonic boom”. This is the loud, cracking sound that is associated with the shock waves that are created by an object traveling faster than the local speed of sound. Examples range an aircraft breaking the sound barrier to miniature booms caused by bullets flying by, or the crack of a bullwhip.
Speed of Sound:
Basically, the speed of sound is the distance traveled in a certain amount of time by a sound wave as it propagates through an elastic medium. As already noted, this is not a universal value, but comes down to the composition of the medium and the conditions of that medium. When we talk of the speed of sound, we refer to the speed of sound in Earth’s atmosphere. But even that is subject to variation.
However, scientists tend to rely on the speed of sound as measured in dry air (i.e. low humidity) and at a temperature of 20 °C (68 °F) as the standard. Under these conditions, the local speed of sound is 343 meters per second (1,235 km/h; 767 mph) – or 1 kilometer in 2.91 s and 1 mile in 4.69 s.
Classifications:
As with most ratios, there are approximations and categories that are used to measure the speed of the object in relation to the sound barrier. This gives us the categories of subsonic, transonic, supersonic, and hypersonic. This categorization system is often used to classify aircraft or spacecraft, the minimum requirement being that most of the craft classified have the ability to approach or exceed the speed of sound.
The Cessna 172, a commercial, propeller-driven aircraft that is classified as subsonic. Credit: Wikipedia Commons/Adrian Pingstone
For aircraft or any object that flies at a speed below the sound barrier, the classification of subsonic applies. This category includes most commuter jets and small commercial aircraft, though some exceptions have been noted (i.e. supersonic commercial jets like the Concorde).
Since these craft never meet or exceed the speed of sound, they will have a Mach number that is less than one and therefore expressed in decimal form – i.e. less than Mach 0.8 (273 m/s; 980 km/h; 609 mph). Typically, these aircraft are propeller-driven and tend to have high aspect-ratio (slender) wings and rounded features.
The designation of transonic applies to a condition of flight where a range of airflow velocities exist around and past the aircraft. These speeds are concurrently below, at, and above the speed of sound, ranging from Mach 0.8 to 1.2 (273-409 m/s; 980-1,470 km/h; 609-914 mph). Transonic aircraft nearly always have swept wings, causing the delay of drag-divergence, and are driven by jet engines.
The next category is supersonic aircraft. These are craft that can move beyond the compression of air that is the “sound barrier.” These craft generally have a Mach number of between 1 and 5 (410–1,702 m/s; 1,470–6,126 km/h; 915-3,806 mph). Aircraft designed to fly at supersonic speeds show large differences in their aerodynamic design because of the radical differences in the behavior of flows above Mach 1.
These include sharp edges, thin wing sections, and tail stabilizers (aka. fins) or canards (forewings) that are capable of adjusting. Craft that typically have this designation include modern fighter jets, spy planes (like the SR-71 Blackbird) and the aforementioned Concorde.
The last category is hypersonic, which applies to aircraft that can exceed the speed of Mach 5 and can achieve speeds as high as Mach 10 (1,702–3,403 m/s; 6,126–12,251 km/h; 3,806–7,680 mph). Very few aircraft can move at such speeds, and tend to be rocket-powered (like the X-15), scramjets (like the X-43, or HyperX), or spacecraft that are in the process of leaving Earth’s atmosphere.
Another example is objects entering the Earth’s atmosphere. These can take the form of spacecraft performing re-entry, or meteorites that have passed through and broken up in Earth’s atmosphere. For example, the meteor that entered the skies above the above the small town of Chelyabinsk, Russia, in February of 2013 was traveling at a speed of about 19.16 ± 0.15 km/s (68,436 – 69,516 km/h; 42,524 – 43,195 mph).
In other words, the meteorite was traveling between Mach 55 and 56 when it hit our atmosphere! Given its tremendous speed, when the meteor reached the skies above Chelyabinsk, it created a sonic boom so powerful that it caused extensive damage to thousand of building in six cities across the region. This damage, which included a lot of exploding windows, resulted in 1,500 people being injured.
So how fast is Mach One? The short answer is that it depends on where you are. But in general, it is a speed that exceeds about 1200 km/h or 750 mph. If you’re capable of going this fast, you will be breaking the sound barrier, and people for miles around will be hearing about it!
I look forward to all the future missions that NASA is going to be sending out in the Solar System. Here, check this out. You can use NASA’s website to show you all the future missions. Here’s everything planned for the future, here’s everything going to Mars.
Now, let’s look and see what missions are planned for the outer planets of the Solar System, especially Uranus and Neptune. Oh, that’s so sad… there’s nothing.
Uranus, seen by Voyager 2. Image credit: NASA/JPL
It’s been decades since humanity had an up close look at Uranus and Neptune. For Uranus, it was Voyager 2, which swept through the system in 1986. We got just a few tantalizing photographs of the ice giant planet and it’s moons.
Mosaic of the four highest-resolution images of Ariel taken by the Voyager 2 space probe during its 1986 flyby of Uranus. Credit: NASA/JPL
What’s that?
Oberon, as imaged by the Voyager 2 probe during its flyby on Jan. 24, 1986. Credit: NASA
What’s going on there?
Color composite of the Uranian satellite Miranda, taken by Voyager 2 on Jan. 24, 1986, from a distance of 147,000 km (91,000 mi). Credit: NASA/JPL
What are those strange features? Sorry, insufficient data.
And then Voyager 2 did the same, zipping past Neptune in 1989.
Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL
Check this out.
Neptune’s largest moon Triton photographed on August 25, 1989 by Voyager 2. Credit: NASA
What’s going here on Triton? Wouldn’t you like to know more? Well, too bad! You can’t it’s done, that’s all you get.
Don’t get me wrong, I’m glad we’ve studied all these other worlds. I’m glad we’ve had orbiters at Mercury, Venus, everything at Mars, Jupiter, and especially Saturn. We’ve seen Ceres and Vesta, and the Moon up close. We even got a flyby of Pluto and Charon.
It’s time to go back to Uranus and Neptune, this time to stay.
And I’m not the only one who feels this way.
Scientists at NASA recently published a report called the Ice Giant Mission Study, and it’s all about various missions that could be sent to explore Uranus, Neptune and their fascinating moons.
The team of scientists who worked on the study considered a range of potential missions to the ice giants, and in the end settled on four potential missions; three that could go to Uranus, and one headed for Neptune. Each of them would cost roughly $2 billion.
Uranus is closer, easier to get to, and the obvious first destination of a targeted mission. For Uranus, NASA considered three probes.
The first idea is a flyby mission, which will sweep past Uranus gathering as much science as it can. This is what Voyager 2 did, and more recently what NASA’s New Horizons did at Pluto. In addition, it would have a separate probe, like the Cassini and Galileo missions, that would detach and go into the atmosphere to sample the composition below the cloudtops. The mission would be heavy and require an Atlas V rocket with the same configuration that sent Curiosity to Mars. The flight time would take 10 years.
NASA’s Curiosity Mars Science Laboratory (MSL) rover blasts off for Mars atop a stunningly beautiful Atlas V rocket. Credit: Ken Kremer – kenkremer.com
The main science goal of this mission would be to study the composition of Uranus. It would make some other measurements of the system as it passed through, but it would just be a glimpse. Better than Voyager, but nothing like Cassini’s decade plus observations of Saturn.
I like where this is going, but I’m going to hold out for something better.
The next idea is an orbiter. Now we’re talking! It would have all the same instruments as the flyby and the detachable probe. But because it would be an orbiter, it would require much more propellant. It would have triple the launch mass of the flyby mission, which means a heavier Atlas V rocket. And a slightly longer flight time; 12 years instead of 10 for the flyby.
Because it would remain at Uranus for at least 3 years, it would be able to do an extensive analysis of the planet and its rings and moons. But because of the atmospheric probe, it wouldn’t have enough mass for more instruments. It would have more time at Uranus, but not a much better set of tools to study it with.
Okay, let’s keep going. The next idea is an orbiter, but without the detachable probe. Instead, it’ll have the full suite of 15 scientific instruments, to study Uranus from every angle. We’re talking visible, doppler, infrared, ultraviolet, thermal, dust, and a fancy wide angle camera to give us those sweet planetary pictures we like to see.
Study Uranus? Yes please. But while we’re at it, let’s also sent a spacecraft to Neptune.
The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into a equivalent 95 minute exposure, and the ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).
As part of the Ice Giants Study, the researchers looked at what kind of missions would be possible. In this case, they settled on a single recommended mission. A huge orbiter with an additional atmospheric probe. This mission would be almost twice as massive as the heaviest Uranus mission, so it would need a Delta IV Heavy rocket to even get out to Neptune.
As it approached Neptune, the mission would release an atmospheric probe to descend beneath the cloudtops and sample what’s down there. The orbiter would then spend an additional 2 years in the environment of Neptune, studying the planet and its moons and rings. It would give us a chance to see its fascinating moon Triton up close, which seems to be a captured Kuiper Belt Object.
Unfortunately there’s no perfect grand tour trajectory available to us any more, where a single spacecraft could visit all the large planets in the Solar System. Missions to Uranus and Neptune will have to be separate, however, if NASA’s Space Launch System gets going, it could carry probes for both destinations and launch them together.
The goal of these missions is the science. We want to understand the ice giants of the outer Solar System, which are quite different from both the inner terrestrial planets and the gas giants Jupiter and Saturn.
The Solar System. Credit: NASA
The gas giants are mostly hydrogen and helium, like the Sun. But the ice giants are 65% water and other ices made from methane and ammonia. But it’s not like they’re big blobs of water, or even frozen water. Because of their huge gravity, the ice giants crush this material with enormous pressure and temperature.
What happens when you crush water under this much pressure? It would all depend on the temperature and pressure. There could be different types of ice down there. At one level, it could be an electrically conductive soup of hydrogen and oxygen, and then further down, you might get crystallized oxygen with hydrogen ions running through it.
Hailstones made of diamond could form out of the carbon-rich methane and fall down through the layers of the planets, settling within a molten carbon core. What I’m saying is, it could be pretty strange down there.
We know that ice giants are common in the galaxy, in fact, they’ve made up the majority of the extrasolar planets discovered so far. By better understanding the ones we have right here in our own Solar System, we can get a sense of the distant extrasolar planets turning up. We’ll be better able to distinguish between the super earths and mini-neptunes.
Artist’s impression of the Milky Way’s 100 billion exoplanets. Credit: NASA, ESA, and M. Kornmesser (ESO)
Another big question is how these planets formed in the first place. In their current models, most planetary astronomers think these planets had very short time windows to form. They needed to have massive enough cores to scoop up all that material before the newly forming Sun’s solar wind blasted it all out into space. And yet, why are these kinds of planets so common in the Universe?
The NASA mission planners developed a total of 12 science objectives for these missions, focusing on the composition of the planets and their atmospheres. And if there’s time, they’d like to know about how heat moves around, their constellations of rings and moons. They’d especially like to investigate Neptune’s moons Triton, which looks like a captured Kuiper Belt Object, as it orbits in the reverse direction from all the other moons in the Solar System.
In terms of science, the two worlds are very similar. But because Neptune has Triton. If I had to choose, I’d go with a Neptune mission.
Neptune and its large moon Triton as seen by Voyager 2 on August 28th, 1989. (Credit: NASA).
Are you excited? I’m excited. Here’s the bad news. According to NASA, the best launch windows for these missions would be 2029 or 2034. And that’s just the launch time, the flight time is an additional decade or more on top of that. In other words, the first photos from a Uranus flyby could happen in 2039 or 2035, while orbiters could arrive at either planet in the 2040s. I’m sure my future grandchildren will enjoy watching these missions arrive.
But then, we have to keep everything in perspective. NASA’s Cassini mission was under development in the 1980s. It didn’t launch until 1997, and it didn’t get to Saturn until 2004. It’s been almost 20 years since that launch, and almost 40 years since they started working on it.
I guess we need to be more patient. I can be patient.
