TransAstra's Asteroid Mining Proposal

[RuBisCO]

This company is further along in developing asteroid mining then any other company I have seen. They even have spent a few million dollars in developing a 250 kg prototype to be placed in orbit with a synthetic baskball size asteroid to "mine". Utilizing sunlight with as few energy conversions as possible asteroid material is heated to boil out all the water, water is collected and again with solarthermal power is used as steam with an engine capable of up to 360 s of Isp. The goal seems to be to aim an NEO to be capture into high earth orbit via a lunar gravity capture. Once in earth orbit the remaining water can be used as propellant for spaceships and the asteroid slag can be refined into metals and what not.  The biggist version of their mining ship they propose can barely fit inside as Starship but could mine a 30 m wide asteroid of ~35,000 tons, extracting 3500~7000 tons of water. With two 30 m wide mirrors it has over 1 megawatt of solarthermal power to work with. 

[Spacescifi]

19 minutes ago, RuBisCO said:

This company is further along in developing asteroid mining then any other company I have seen. They even have spent a few million dollars in developing a 250 kg prototype to be placed in orbit with a synthetic baskball size asteroid to "mine". Utilizing sunlight with as few energy conversions as possible asteroid material is heated to boil out all the water, water is collected and again with solarthermal power is used as steam with an engine capable of up to 360 s of Isp. The goal seems to be to aim an NEO to be capture into high earth orbit via a lunar gravity capture. Once in earth orbit the remaining water can be used as propellant for spaceships and the asteroid slag can be refined into metals and what not.  The biggist version of their mining ship they propose can barely fit inside as Starship but could mine a 30 m wide asteroid of ~35,000 tons, extracting 3500~7000 tons of water. With two 30 m wide mirrors it has over 1 megawatt of solarthermal power to work with. 

 

The future looks like a lot of mirrors in space.

Why not? Free energy! Use it.

If KSP taught me anything it is that spacecraft need to be as low mass as you can manage.

Going heavy like starship makes trying to land the thing a good deal harder.

Edited January 3, 2021 by Spacescifi

[Shpaget]

45 minutes ago, RuBisCO said:

solarthermal power is used as steam with an engine capable of up to 360 s of Isp.

360 s sounds a bit high for steam rocket.

45 minutes ago, RuBisCO said:

With two 30 m wide mirrors it has over 1 megawatt of solarthermal power to work with. 

In Earth orbit. In main belt they'll provide only about 10% of that.

[RuBisCO]

3 minutes ago, Spacescifi said:

 

The future looks like a lot of mirrors in space.

Why not? Free energy! Use it.

If KSP taught me anything it is that spacecraft need to be as low mass as you can manage.

Going heavy like starship makes trying to land the thing a good deal harder.

Yes if this was to be done electrically instead of solar thermal then you have the conversion loses of sun light to electricity (40% max efficency so 60% loss) then conversion to grinders and laser and heater to cook the asteroid material. There is advantage to going solar electric over solar thermal in that potentially asteroid material could be much further refined. Using hydrogen or carbon monoxide reduction asteroid material could be refined and even seperated into metal types, but electrolysis cells are requires to recycling the water and CO2 produced, but oxygen would be produced in such abundance it could be used as fuel in a ion engine. This would allow for almost all the water to be retained (hydrogen) while reducing asteroid material further to metal, but the energy cost would be an order of magnitude more and yet for the same array area only a fraction as much energy would be provided, plus the mass of electrolysis cells, radiators, ovens, and all the added problems that technology provides.

13 minutes ago, Shpaget said:

360 s sounds a bit high for steam rocket.

In Earth orbit. In main belt they'll provide only about 10% of that.

360 s at over 2500 K is perfectly viable, even under performing likely because of low pressures. They are going to NEO that is in earth like orbits with earth like distances from the sun. 

https://www.transastracorp.com/deep-space-propulsion.html

[YNM]

2 hours ago, RuBisCO said:

30 m wide asteroid of ~35,000 tons, extracting 3500~7000 tons of water.

Seems like they'd have to scout around for a water-rich asteroid then. C-type asteroid 101955 Bennu (sampled by OSIRIS-REx) is at least only 1% water by weight from close-range spectroscopic measurements, while S-type 25143 Itokawa is about .051% water from sample analysis. C-type is the ones that are expected to have more water in general (and indeed up to 12% water by weight have been predicted) but they're found more on the outer parts of the Main Asteroid Belt.

[kerbiloid]

(Melancholically looks at the famous 16 Psyche average density (~4.2) comparing it to the really deserving that mining actinoids, platinoids, and lantanoids (10 .. 20)).

[YNM]

It's way more massive than the 30 m capture horn, so no.

 

1998 KY26 is about 30 m in diameter, and is somewhat water-rich (X-type), would be visited by Hayabusa2 (extended mission) in July 2031. Sample from Bennu is returning in September 2023, so maybe we'll have to see if the water content expectations are realistic or not.

Edited January 3, 2021 by YNM

[RuBisCO]

1 hour ago, YNM said:

Seems like they'd have to scout around for a water-rich asteroid then. C-type asteroid 101955 Bennu (sampled by OSIRIS-REx) is at least only 1% water by weight from close-range spectroscopic measurements, while S-type 25143 Itokawa is about .051% water from sample analysis. C-type is the ones that are expected to have more water in general (and indeed up to 12% water by weight have been predicted) but they're found more on the outer parts of the Main Asteroid Belt.

They claim they will use a C-type asteroid of 10%~20% water in hydrates. NEO of such are still get knocked in from jupiter from time to time.

[YNM]

10 hours ago, RuBisCO said:

They claim they will use a C-type asteroid of 10%~20% water in hydrates. NEO of such are still get knocked in from jupiter from time to time.

Do they currently have any candidates, or a program to scout potential objects ? If they did found one, would they send a sampling mission (or just a close-observation probe in general) to it to examine the feasibility ?

 

I'm asking all these because they will have to rely a lot on the amount of water they can get out of the captured object. If it turns out that the kind of bodies that they're seeking is really hard to find, then one might call the architecture unworkable. One would need to worry what exactly they will be able to mine as well (given the high-water-content asteroids all usually have more organics on it than metals - that might actually be more desirable in outer space), but if the mission design remains to rely on water then the water content is mission-critical.

Edited January 4, 2021 by YNM

[RuBisCO]

7 hours ago, YNM said:

Do they currently have any candidates, or a program to scout potential objects ? If they did found one, would they send a sampling mission (or just a close-observation probe in general) to it to examine the feasibility ?

 

I'm asking all these because they will have to rely a lot on the amount of water they can get out of the captured object. If it turns out that the kind of bodies that they're seeking is really hard to find, then one might call the architecture unworkable. One would need to worry what exactly they will be able to mine as well (given the high-water-content asteroids all usually have more organics on it than metals - that might actually be more desirable in outer space), but if the mission design remains to rely on water then the water content is mission-critical.

There present candidate is an asteroid simulant they launch with their tiny prototype:

I agree that what they are proposing is limited to asteroids of high water content if they plan to return asteroid material to earth orbit, but to implement and more advance system that used hydrogen or CO recycling with electrolysis cells and and oxygen ion engines, etc, would take many more years of research and money. For the mean time they claim there are ~600 "economically viable" asteroids of >5 m in NEO for them, if you wish to make a counter study disproving this that would be great. 

 

[YNM]

5 hours ago, RuBisCO said:

For the mean time they claim there are ~600 "economically viable" asteroids of >5 m in NEO for them, if you wish to make a counter study disproving this that would be great. 

Lol XD I was just hoping if they did mention a plan to do more scouting - and they did ! The model they use to simulate the dV expenditure uses 4000 "synthetic low-dV target which will have to be discovered". The "~600 candidates" are out of this modelling. Plus they're working closely with NASA so I suppose they know well what they're doing.

At the very least this means that they're aware that they (probably more on NASA's part) need to do a lot of the groundwork, namely to observe and discover lots of small NEAs/NEOs. And another positive thing is that this might mean in both increased vigilance on PHAs, as well as (maybe) increased asteroid sample return missions... I'd definitely wait for us to collect more pristine samples than a mere 65 g of loose medium-sized gravel !

Edited January 4, 2021 by YNM

[Clamp-o-Tron]

They can improve their thruster performance and decrease required propellant (and therefore water content required in their NEO candidates) by using the microwave electro-thermal thruster, using water vapor as reaction mass, getting ~800 seconds of Isp with current engineering levels, at 50 kW. 50 kW is really a lot, so I suspect that steam propulsion would probably be better if they didn't want to put massive solar panels on their bees.

[RuBisCO]

3 hours ago, YNM said:

Lol XD I was just hoping if they did mention a plan to do more scouting - and they did ! The model they use to simulate the dV expenditure uses 4000 "synthetic low-dV target which will have to be discovered". Plus they're working closely with NASA so I suppose they know well what they're doing.

At the very least this means that they're aware that they (probably more on NASA's part) need to do a lot of the groundwork, namely to observe and discover lots of small NEAs/NEOs. And another positive thing is that this might mean in both increased vigilance on PHAs, as well as (maybe) increased asteroid sample return missions... I'd definitely wait for us to collect more pristine samples than a mere 65 g of loose medium-sized gravel !

They might also get defense funding because their data could also double in detecting impactors before impact. Remember even the little ones can still level a city, 2013 Chelyabinsk meteor was just 20 m wide and did 500 kiloton blast!

[YNM]

12 hours ago, RuBisCO said:

Remember even the little ones can still level a city, 2013 Chelyabinsk meteor was just 20 m wide and did 500 kiloton blast!

Yep, and currently we may as well be totally blind to those objects.

12 hours ago, Clamp-o-Tron said:

They can improve their thruster performance and decrease required propellant (and therefore water content required in their NEO candidates) by using the microwave electro-thermal thruster, using water vapor as reaction mass, getting ~800 seconds of Isp with current engineering levels, at 50 kW.

Huh, so basically like ion engines but for water, and instead of an ion-plasma generator it's an open-end microwave...

Honestly I was wondering why they didn't propose to use a variation of ion engine or such. It is low thrust but you would do near-constant thrusting in some way anyway I suppose...

Edited January 5, 2021 by YNM

[RuBisCO]

1 minute ago, YNM said:

Huh, so basically like ion engines but for water, and instead of an ion-plasma generator it's an open-end microwave...

Honestly I was wondering why they didn't propose to use a variation of ion engine or such. It is low Isp but you would do near-constant thrusting in some way anyway I suppose...

Solar to electric is a major conversion loss of energy, but if they are going to go that route, which I think eventually is best, I would think solar-themal-electric would be best so they can still use solar heat for extraction and reforming while also using it to drive brayton cycle generators, which would power electrolysis for recycling hydrogen and carbon monoxide for reducing and reforming asteroid materials into metals, in the process excess oxygen would be the by-product that could then be used in a ~1500 s Isp ion engine.

The next problem is thrust to weight: lets say you have 30000 tons of miner and asteroid, and 1 Megawatt solar thermal to work with, a 350 s Isp thermal rocket with 50% efficiency could do 291 N of thrust, and accelerate the whole thing 1 m/s in 1.2 days while consuming 7334 kg of propellant. If an ion engine is used, lets say with solar thermal to electricity efficiency of 35% and Ion engine efficiency of 70% (thus a total of 24.5% efficiency) it would take 10.4 days to accelerate 1 m/s but only use 196 kg of oxygen.

I did not add in the added cost of making that oxygen, we need electrolysis cells of at best 75% efficiency using electricity and solar heating in a solid oxide reverse fuel cell, we need to not only boil the asteroid material but melt it in hydrogen gas at 1000 to 2000 K to reduce it to metals and extract much of the oxygen. Lets assume 5% total efficiency cracking oxygen out of asteroid material, that means 2832 MJ/kg for oxygen or 6.4 days needed to make enough oxygen, so 10.4+6.4=16.8 days for 1 m/s acceleration.

The biggest problem though is making a complex solar thermal-electro-chemical processing facility that can operate autonomously millions of kilometers away from human operators. These systems will break down a lot especially with god only knows what hydrogen sulfide, ammonia, chloride, protomolecule, etc, content in the asteroid it is chewing up. The pure solar thermal option transastra is working on removes that complexity and thus improves reliability.

[Clamp-o-Tron]

11 minutes ago, YNM said:

Huh, so basically like ion engines but for water, and instead of an ion-plasma generator it's an open-end microwave...

Honestly I was wondering why they didn't propose to use a variation of ion engine or such. It is low Isp but you would do near-constant thrusting in some way anyway I suppose...

Yeah, ion thrusters would be a good idea. Using ~360 Isp steam thrusters will need 1.3 tonnes of propellant to get 1 km/s on the 4 tonne initial prospector, but less than 100 kg of Xenon with the performance of the NEXT ion thruster. If they want to stick to water and have a good power source for the MET, 550 kg of water should be good.

As for required thrust, just about any amount will work. The only time when (relatively, we're talking about blistering, spine-crushing forces of MULTIPLE NEWTONS!) high thrust would be required would be capture into Lunar or high Earth orbit, which could just be done by exploiting n-body weirdness with a gravitational capture. For the rest of the time, multi-month burns would be just fine for maneuvering in heliocentric orbit.

[kerbiloid]

15 hours ago, RuBisCO said:

For the mean time they claim there are ~600 "economically viable" asteroids of >5 m in NEO for them, if you wish to make a counter study disproving this that would be great. 

Spoiler

It's just one of metallurgical quarries, and it's 500 meters deep.

How many of 5-m  potentially minable asteroids can be placed inside?

And it has air, water, and electricity right now.

[YNM]

11 hours ago, RuBisCO said:

The biggest problem though is making a complex solar thermal-electro-chemical processing facility that can operate autonomously millions of kilometers away from human operators.

Think the Parker Solar Probe and OSIRIS-REx is capable of some advanced autonomous operations (that means that it was not pre-programmed, and it's more than stationkeeping).

2 hours ago, kerbiloid said:

It's just one of metallurgical quarries, and it's 500 meters deep.

In outer space, organic materials might be the one of relatively rare materials, so organic-containing asteroids would be the one that they seek more. (Barring just skipping to the gas giant's moons, of course.)

[kerbiloid]

2 hours ago, YNM said:

In outer space, organic materials might be the one of relatively rare materials, so organic-containing asteroids would be the one that they seek more.

But to reach that asteroid they should spend more organics than get from there to any another planet.

While Mars has its own C,H,N, and Titan does. Probably Triton and Pluto, too. 

At the Jupiter they should better mine this on Io or somewhere else than import from asteroids.
And anyway, delta-V required to deliver solid carbon in bricks from Earth or Mars to anywhere still makes them more reliable source of organics than asteroids.

[YNM]

1 hour ago, kerbiloid said:

But to reach that asteroid they should spend more organics than get from there to any another planet.

Well, that's the idea of why they want to use the water in the asteroids itself. The amount of CH required to do the initial capture is much smaller compared to the amount one would need to take the materials back.

Also I'm thinking that the target bodies to be served are for, say, a moon outpost, or an orbiting station (still think that it's much better for mobility compared to planetary surface bases). Plus the technology could become usable once we get to the gas giants to capture smaller objects (which does exist, given dust rings).

[RuBisCO]

On 1/5/2021 at 1:46 AM, YNM said:

Think the Parker Solar Probe and OSIRIS-REx is capable of some advanced autonomous operations (that means that it was not pre-programmed, and it's more than stationkeeping).

In outer space, organic materials might be the one of relatively rare materials, so organic-containing asteroids would be the one that they seek more. (Barring just skipping to the gas giant's moons, of course.)

Well the problem is that electrolysis cells are going to get gunched up, thermal cycling is going to cause things to break, contaminates are going to corrode pipes and channels, etc, someone or something smart enough to do complex repairs is required on station at all times to keep things running. 

I agree that storing and utilizing the carbon and hydrogen is preferable to dumping it overboard as propellant in a ~350 isp solarthermal engine. Oxygen will be the biggest by-product from reducing asteroid material, while not as oxidize as earth rock up to 25% of an asteroid is oxygen, a few percent of that oxygen in Hall Effect Thrusters of ~1500 isp would provide all the attitude control and orbital tuning to put asteroids in high earth orbit via a lunar gravity assist capture, while wasting none of the more precious water and carbon.

[YNM]

8 minutes ago, RuBisCO said:

someone or something smart enough to do complex repairs is required on station at all times to keep things running. 

We've got machines that'll assemble things without a human, we've got machines that will disassemble anything without a human, but we haven't got a repairing machine that isn't controlled in each step by a human, indeed.

Part of the reason why these days they don't really like the idea of repairing stuff... otherwise their machine investment is going to go nowhere.

Edited January 8, 2021 by YNM

[radonek]

If this is viable, can they even be allowed to actually use it? Like, on a real rock? Because pushing actual asteroid onto near-earth trajectory does have certain implications.

[YNM]

6 hours ago, radonek said:

pushing actual asteroid onto near-earth trajectory does have certain implications.

They're planning to use NEAs exclusively. Their simulations involve "4000 random low delta-V targets" and they determined that 600 of them could be in a viable position. A lot of the bodies will have to be discovered first I presume.

[radonek]

3 hours ago, YNM said:

They're planning to use NEAs exclusively. Their simulations involve "4000 random low delta-V targets" and they determined that 600 of them could be in a viable position. A lot of the bodies will have to be discovered first I presume.

I am not talking about target selection. I am talking about weaponization. Anyone who can move rock to Earth orbit can also push it to collision course. Much less potentially destructive industries are heavily regulated everywhere and for a good reason.