NASA Unveils Two New Missions To Study Truly Strange Asteroids (space.com)

An anonymous reader quotes a report from Space.com: NASA's next low-cost planetary missions will attempt to unravel the mysteries of some seriously bizarre asteroids. The space agency has selected projects called Lucy and Psyche via its Discovery Program, which funds highly focused space missions to destinations throughout the solar system. The Lucy project will investigate the Trojan asteroids, which share an orbit with Jupiter, while Psyche will journey to the asteroid belt to study a huge, metallic asteroid named 16 Psyche that resides there. Lucy is scheduled to launch in October 2021. If all goes according to plan, the probe will visit an asteroid in the main asteroid belt -- located between Mars and Jupiter -- in 2025, and then go on to study six Trojan asteroids between 2027 and 2033, NASA officials said. There are two streams of Trojan asteroids. One trails Jupiter, and the other leads the giant planet around the sun. Scientists think both streams may be planetary building blocks that formed far from the sun before being captured into their current orbits by Jupiter's powerful gravity. Psyche will explore one of the oddest objects in the solar system -- a 130-mile-wide (210 kilometers) metallic asteroid that may be the core of an ancient, Mars-size planet. Violent collisions billions of years ago might have stripped away the layers of rock that once lay atop this metallic object, scientists say. Psyche is scheduled to launch in October 2023 and arrive at the asteroid in 2030, NASA officials said.

Comments

Re:This is truly great news!

[michelcolman]

Asteroids trailing and leading Jupiter? Does that mean Jupiter hasn't cleared its orbit? I guess Jupiter is a dwarf planet then!

And NEOCam is on Life Support

[mbone]

The asteroid finding satellite NEOCam was one of the candidates that didn't get selected, but it has strong institutional support at NASA. Jim Green announced that NEOCam would get one year of additional "Phase A" (i.e., life support) funding, presumably as they try and find a way to fund it.

Re:And NEOCam is on Life Support

[Rei]

I was never really feeling NEOCam. It's not looking for earth-killers, just Tunguska-sized impactors. We've got LSST coming online in the early 2020s which will greatly increase our detection rate, and there will be more in the future. If anything, LSST is significantly better than NEOCam (p.38). A 5-10 years setback (counting for the complimentary nature of the two approaches - NEOCam is IR, LSST visible) is extremely unlikely to equate to "losing New York city" or anything of that nature. A Tunguska-scale impactor is a roughly one-in-400 year event, and overwhelmingly likely to impact few to no people. The odds of one hitting a major metropolitan area in that timeframe, which we could have stopped had we known about it, are one in millions. NeoCAM costs $500m. The delay seems acceptable to me, in an area where space budgets are tight.

If there is an imminent earth-killer out there, it's not in the inner solar system. It's a comet. And neither NEOCam nor LSST would likely see it until it was well on its way toward us. Smaller but still devastating comets? Even later. Hence, defense against large impactors has to be nuclear - as large of warhead(s) as possible, mounted to a storable rocket that can achieve significant delta-V. Nothing else but nuclear has the energy density to deflect in such a short time period, and you don't have the time to engineer your deflection craft from scratch and integrate it onto a stack when time is that short. So if we're serious about planetary defense, that's an approach we need to take.

All of this said: I do kind of look forward to the day when we know the orbits of a large chunk of the ~30-40m impactors and a fair minority of the ~20m (Chelyabinsk-sized) impactors. Because those hit often enough somewhere on the planet (generally very remote) that people could actually travel to see them, like people do with eclipses. And that would be a really neat experience :) And I can totally imagine meteorite hunters prepositioning hardware near the likely strewn field.

Re:And NEOCam is on Life Support

[Rei]

There is no shockwave. Instead, the energy remains predominantly X-rays. These penetrate into the surface and rapidly convert it to plasma, which sends a powerful burst of plasma, gas and debris in one direction and a powerful shockwave through the object, shattering it and imparting momentum to the fragments.

There's a common myth (sometimes even promoted by scientists who haven't worked on the issue of asteroid deflection) that using a nuclear warhead against an asteroid means that you'll just split it into pieces that are even more destructive than it was before. This is not in accordance with the actual peer-reviewed literature on the subject. There've been a number of projects to do supercomputer simulations, and the results of nuclear deflection - both through standoff "pushing" or direct high-intensity surface impact - are better than even hoped. With very reasonable sized nuclear weapons (compared to the size of the body) you can break asteroids into pieces that tend to be very small, moving at velocities well too fast for it to recoalesce. You can also very readily impart an impulse to significantly change the asteroid's trajectory, whether you destroy it or not.

And even if this wasn't the case, researchers in the field are far from in agreement that one large impactor is worse than multiple smaller impactors; smaller impactors aren't as good at excavating material, and the fact that they're spaced out in time reduces the peak heating for the most "survivable" areas. And of course pieces below a certain size suffer a great deal of ablation and/or decleration and excavate nothing. Larger pieces that airburst, while they flash a large area, usually airburst high enough that surface damage can be limited in the damage zone (see, for example, Chelyabinsk - was that really worse than detonating a 500kT bomb at the surface?), and likewise excavate little to no material.

Re:And NEOCam is on Life Support

[johannesg]

All of this makes me think we most definitely need to run a few experiments on changing asteroid orbits. First, and most importantly, because it gives us experience with doing so that may one day prove absolutely vital to our survival. And second, because setting of nukes in space and messing with the orbits of celestial bodies is just totally awesome.

Re:And NEOCam is on Life Support

[necro81]

I was under the impression that setting off a nuke on an impactor only works in movies. In reality there is no atmosphere, therefore almost no shockwave, and the object continues approaching on the same vector and with the same mass.

The people who developed Project Orion would beg to differ. A nuclear blast in proximity to a solid object can definitely provide impulse.

Re:This is truly great news!

[Rei]

The "cleared" term is generally understood to have been poorly worded, with most preferring "gravitationally dominant" to be better. The Trojans are trapped in their location specifically because of Jupiter, not in spite of it.

Then again, if we want to get nitpicky, Jupiter fails the planet definition because the point it orbits (the Sun-Jupiter barycentre) is not inside the sun. They corotate an empty point in space rather than Jupiter simply "orbiting the sun" as the definition requires ;)

But that's being nitpicky. I have much bigger complaints with the planet definition than that.

Give me some steel working Men!

[Invisible Now]

Psyche 16 is a heavy mass of iron. Already well out of the gravity well of the Sun. Give me a few resourceful and creative engineers (The challenge will be way too demanding for AI and Too far away from earth for near real-time robotics) and all I need is an energy source. With our minds and Promethean effort Iwe can craft an iron or steel (using easily scavenged local carbon )space ship forged in space). Then we’ll use the energy source, magnetism from the conductive iron and Iron ions to create an impulse drive to power our beautiful large Beam and Plate habitat on an epic voyage !. It’s all straight forward conventional physics Steel water tanks we’ll fill on the fly from Ice we find drifting out there like cometary space icebergs.. atmosphere by electrolysis. Calling on all you brave sons of Pittsburg! Imagine what we can do! We’ll make the Martian look like the dirt farmer he was!

Contrary to the artist illustrations...

[Rei]

I fully expect the surface to be pitted and covered in regolith/debris.

Which IMHO would actually be a good thing. If we're ever to engage in asteroid mining, the last thing you want is to be having to fracture and pulverize everything yourself; you just want to have to load it (which is hard enough in microgravity) into a mold, sinter it into an ideal reentry shape, and electromagnetically eject it onto an ideal Earth-crossing trajectory for controlled aerobrake/aerocapture (either one-stage: aerocapture straight to the surface, with a larger landing ellipse - or two stage: aerobrake to LEO, then do a timed burn to land within a very narrow ellipse). The latter requires a docking or disposable thruster(s) for each return, while the former can be a simple unguided projectile - so there's a tradeoff between how much land you have to allocate for your returns, and how much those returns cost per unit mass.

A landing ellipse on land doesn't need to be empty of people, but it needs to be able to be emptied of people; returns would arrive in waves, not at an even rate, so it'd be fine to continue using the land for farming, grazing, etc in the interim. An alternative would be to sinter enough voids into the reentry bodies so that they float, then land them in open ocean in a place where currents will concentrate them.

Asteroid mining is anything but a short term option. But it's interesting for the long term. You've got some very high concentrations of precious metals (and some gemstones, like peridot), concentrations that rival or exceed the best mines on Earth, with zero overburden. And products made from them would command a premium on the market - a huge premium in the early days.

Re:Contrary to the artist illustrations...

[Rei]

The value of things mined from asteroids at present is zero. There is zero market. There is, however, a market for precious metals and gemstones here. Particularly if they're "exotic"

ISRU is something that could be very useful in the future, but first you have to develop the market for it. Meanwhile, in order to develop that market, people are working to undercut launch costs. Which undercuts the value of said resources being in space.

And ISRU is not nearly as simple as people like to think of it. Let's forget about some sort of "spacedocks" welding together spaceships out of asteroid nickel-iron for now, let's stick to the "easy" stuff, like water for a Marsbound spacecraft. Let's say that what you sinter together is only rock on the outside,but mined permafrost on the inside, so the rock can ablate and protect the sandy ice inside for aerocapture at Earth. Let's ignore how this is harder than just sintering regolith alone. How do you make use of what arrives at Earth? First you have to maneuver a spacecraft to dock with each chunk in LEO (after detecting them with radar), then drag it back to where you're assembling your spacecraft. You then need to drill/cut into each one in space. You then need to put it into a boiler to vaporize out the ice. The boiler needs to maintain a high enough internal pressure that water can exist in a liquid state (otherwise it'll just freeze out as ice and cause you difficulty in getting it into your tanks). So you have a condenser, and pumps connected to your tanks, and you fill them that way. If there's any other volatile chemicals in there that were in the rock (organics, ammonia, etc), you'll need to run your water through reverse osmosis or similar. And of course, any humans involved in this process have to be supported during all this time with consumables from Earth.

Or, you could save yourself all of the time, engineering expense, hardware launches, etc, and just simply launch the water to begin with.

When faced with such decisions, people usually choose the latter.

When it comes to sending mined material to the surface of the Earth, however, the situation is a bit different. Your asteroid still needs a regolith/rock gathering rover, a sinterer, a coilgun, and a power source, all delivered to an asteroid's surface. A project that's probably on the order of a few billion dollars when all is said and done. But all of your other costs are normal Earth costs, everything done on the surface of the planet. You have a chunk of land or sea where precious metal-rich rocks rain down from the sky every X months in a storm of fireballs. Radar tells you where they came in (yes, you actually can see meteors on radar!). A first generation mining operation (whether the landing site would be at land or on sea) would probably work with rocks that weigh just a tonne or less each, and would involve taking them back to a processing facility; however more advanced operations might involve rocks massing hundreds or even thousands of tonnes, and mobile processing facilities. It's not clear what the upper bound on survivable sizes would be, or whether there even really is one. Natural (aka, not optimally shaped, not optimally targeted) meteorites found on Earth get up into the dozens of tonnes each. And you can always include more void space into the sintered shape to increase your surface area to mass ratio and thus entry survivability

Re:Insert snarky slashdot comment here

[Anonymous Coward]

You should post in every thread.

We already learned to walk...

[tlambert]

It is important to learn to walk before you attempt to run. In case you cannot wait, we'd be happy to strap your ass to rocket and send you to the nearest star. Please write often, we'd love to hear how it is going.

We already learned to walk... you're probably a millennial who was not there on July 20th, 1969 when we took our first steps. That almost 50 years ago this year. Guess what we were learning to do in 1919, 50 years before that? We had just completed the first non-stop transatlantic flight.

50 years before that, the biggest deal in 1869 was closing on the funding for the Beach Pneumatic railway... and it was 10 years before Edison demonstrated his electric light bulb in Menlo Park.

We are sitting around these days, mostly staring at our belly button lint. But we are proud of ourselves, for using robots to do it. It turns out it's the same belly button lint that was there in 1969.

We seem to be saddled with an overabundance of one of:

1. Caution
2. Roboticists, sucking the funding out of everything interesting
3. People with sticks up their asses

Pick one, but we should have a colony on the moon already, if not Mars (at least a Phobos base for the asteroid mining fleet).