Colonization Discussion Thread (split from SpaceX)

[sevenperforce]

15 minutes ago, DAL59 said:

It uses the air itself to make fuel.  Thats not a risk, and their prepositioning two BFRs in advance anyway.  

Air can be used to make LOX, but you need to get mine ice for the H₂O to crack into methane.

[DAL59]

You can just take the hydrogen with you, every kg of h2 can be used to produce several kgs of methane and oxygen.  You can also get water from the 100% humidity air.

[DAL59]

5 minutes ago, sevenperforce said:

Also, the atmosphere is so low in water vapor that you're looking at thousands of cubic meters of air per liter of extracted water.

They have 500 days.

[Hannu2]

11 hours ago, DAL59 said:

The sabatier reaction has been done for decades.  

It is very different to do things on another celestial bodies. Sabatier reaction and following refining stages have been made in huge industrial plants under possibility of immediate service if problems arise. It is obviously impossible option on first Mars trips. Reactor and purification stages must be developed to very lightweight, compact and sturdy package which is possible to transport on Mars. And it must be able to produce and store tens of tonnes of fuel without any service. Any problem means mission failure. It is huge engineering problem which takes decades time and billions of dollars before we can even talk realistically about manned missions.

And it is only one small part of whole Mars mission. There are as large and even larger problems in another sectors. Propulsion, habitats, crafts etc. must be developed. We may know at scientific level what they need but all actual devices must be funded, planned, built, tested and certified to use. We know about the history of space tech that it will be very hard and time consuming task.

 

[Hannu2]

17 hours ago, sevenperforce said:

Upthread, I was discussed a reduced-complexity ISRU system, where the ascent vehicle carries its own hydrazine and merely needs to manufacture LOX to fill tanks which were used for descent. A gallium-phosphide semiconductor, combined with a nickel-based alloyed catalyst, can be used to crack CO₂ into CO and O₂ using solar power. So all you need is the solar array, a compressor/collector which can work in a 600-Pa atmosphere, and a gas liquefaction system with a small centrifuge.

This could be tested in LEO on Dragon 1. Send up the Dragon 1 and have it vent to vacuum. It would have a canister filled with 96% CO₂, 2% argon, and 2% N₂, attached to a valve. The valve would release gas at such a rate as to maintain a constant internal capsule pressure of 600 Pa, and then the Dragon 1 would use its thrusters to put itself into a steady tumble to simulate Martian gravity. The ISRU system would kick on and test everything.

Oxidizer is the majority of the propellant mass of an ascent vehicle, so if you can crack it from the atmosphere, you've cut your starting mass down considerably. 

You'd need to test it in LEO, then send a small version with a working filtration system to Mars on a Falcon Heavy for testing (this would be a good time for a Mars Sample Return mission), then send a full-scale ascent vehicle for testing, and THEN you can do your flags-and-footprints landing.

Yes, but at the same time, you do need as much mission safety and redundancy as possible.

The TMI needs to put you on a free-return, so that even if EVERYTHING goes wrong, you can still make it home as long as your life support remains functional and your entry capsule is intact. The orbiter cannot rely on ISRU fuel; it needs to carry enough propellant to brake in and out of low Martian orbit on its own. 

I do not see great value of testing that kind of process in LEO instead of laboratory on Earth. LEO environment simulates only low gravity, but as far as I know (however, I am not expert on that area) gravity is not significant in reactions of gases. Effects of smaller gravity would be easy to calculate. Effects of actual Mars atmosphere, its weather and other variations, dust and other surface phenomena are much harder to predict without tests.

It is true what you say about redundancy. But it is very hard to predict better than guessing what will be chosen strategy. We are so far from it. I am sure that when tests begin they give many surprises which affect the mission and all current ideas will be changed. Is it better to make direct landing and make all fuel for ascent on Mars, or should we use separate landing and ascent module and maybe utilize only local oxygen as you suggest?

11 hours ago, DAL59 said:

 

You can just take the hydrogen with you, every kg of h2 can be used to produce several kgs of methane and oxygen.  You can also get water from the 100% humidity air.

Unfortunately hydrogen is almost impossible to store for long periods. It boils off in few hours if tanks are not refrigerated continuously and there is not practical refrigeration technology suitable for space.

[Green Baron]

I think we are running in circles in the various threads an Mars. We have the enthusiasts like the Mars society who play around with their Pickup trucks, tarps and scaffolds and canned nutrition as well as innumerable others in their backyards or the desert behind the house. If i just think about the fact that they can go to the doctor any time they want it becomes clear to me that this is just playing in the sand box. Nothing against playing :-).

On the other hand there is next to 0 real data even to answer the question where is water, in which form and how can we obtain it. It is all "this looks like", "this may be", "if we assume that ...". Not that that means that our expectations on Marsian soil and atmosphere are completely wrong, but deducting from the sparse data that we just take a couple of black boxes labeled "fuel", "air", "water" and everything is fine is premature.

There are only very few experiments (i know of one, greenhouse in Antarctica at Niemeyer Station, more ?) that were or are undertaken in a controlled environment with at least a scientific background. Relevance is still open. So, in the end, if you want to believe Zubrin et. al. you could just go there, use ready made technology and everything will be fine. In this case it is good that atm there is no vehicle capable of bringing people there, it'll probably end in a disaster.

 

I find it really nice that SpaceX now has a rocket with a significant payload capacity.

Next hype train stations: the first real commercial missions to space with that rocket, human rating of a capsule and subsequently, 2019+ if it is happening at all, the "billionaires around the moon" thing. I am was looking forward to that. Until cancellation ?.

 

Edit: corrections applied, thanks @sh1pman :-) Looks like i wasn't up to date on SpaceX marketing activities

Edited February 13, 2018 by Green Baron

[sh1pman]

6 minutes ago, Green Baron said:

Next hype train stations: the first real commercial missions to space with that rocket, human rating of a capsule and subsequently - 2019+ if it is happening at all, the "billionaires around the moon" thing. I am looking forward to that. Until cancellation ?

"Billionaires around the Moon" was cancelled in favor of BFR.

[sevenperforce]

6 hours ago, CatastrophicFailure said:

I wonder about that a bit. Given that this is rocket science, don’t they know like down to the gram how much TEA-TEB they’re going to need for x amount of relights, or is it a dynamic number that the engine computer has to constantly adjust during startup, making it unpredictable?

The general discussion consensus (which is still speculative) is that the TEA-TEB "valve" is opened and allowed to run continuously until the engine starts. If a particular engine takes longer than usual to start (for example, perhaps because it's coming nozzle-first into the atmosphere at high-hypersonic velocities), more ignition fluid will be consumed.

That's about as much as we'll ever know, I think.

4 hours ago, sh1pman said:

"Billionaires around the Moon" was cancelled in favor of BFR.

Musk was not exactly clear. I believe the contract for a cislunar tourist trip still exists but is planned to be satisfied with BFR rather than FH.

Easier for SpaceX if they don't have to man-rate FH. Reminds me of Constellation, actually. The one good thing about Constellation was the idea to man-rate a smaller vehicle and not the heavy lifter.

5 hours ago, Hannu2 said:

I do not see great value of testing that kind of process in LEO instead of laboratory on Earth. LEO environment simulates only low gravity, but as far as I know (however, I am not expert on that area) gravity is not significant in reactions of gases. Effects of smaller gravity would be easy to calculate. Effects of actual Mars atmosphere, its weather and other variations, dust and other surface phenomena are much harder to predict without tests.

Doing it in lowered gravity would avoid any unforeseen impacts. Centrifuges can be pretty sensitive machines.

5 hours ago, Hannu2 said:

It is true what you say about redundancy. But it is very hard to predict better than guessing what will be chosen strategy. We are so far from it. I am sure that when tests begin they give many surprises which affect the mission and all current ideas will be changed. Is it better to make direct landing and make all fuel for ascent on Mars, or should we use separate landing and ascent module and maybe utilize only local oxygen as you suggest?

Yeah, what are we optimizing for? Are we more concerned about what we can build as fast as possible, or about the lowest mass to TMI, or the highest level of safety/redundancy?

[PB666]

1 hour ago, sevenperforce said:

Doing it in lowered gravity would avoid any unforeseen impacts. Centrifuges can be pretty sensitive machines.

Centrifuges generate alot of heat. Particularly during the initial startup. Even at martian pressures centrifuges generate alot of internal heat. In general a centrifuge would benefit from lower gravity because the stress along the vector of angular momentum is less, but having said that you can have frictionless bearings and take that out. The radius of bearings for centrifuges are intentionally made small for that reason. Within the centrifuge you have a manifold that at some point has a maximum radius (in which is a mass which conducts heat but if the bearing is small net conduction is tiny) it is at the manifold maximum radius that you have collisions at speeds from 10s of meters per second to 100s of meters per second.

The centrifuges we had in our group that were refridgerated required a magnitude more expenditure on issues dealing with vacuum pumps and refrigeration (essentially vacuum pump is part of the cooling system as it lowers the mass flow of gas around rotors)

There are two or more ways to centrifuge a livable object. You could spin the entire object (this includes things that are inductively tied to another object but do not allow passive exchange between inhabitants). The other way is to use a manifold within or extended along another object. The sealing mechanism for end-attached systems is complicated, likely to loose gas mass over time and provide friction. Another way is to put the vessel to be turned inside another vessel, then just collect lost gas and return it to the first. This results in less friction an no net-losses. For example, with a minimal neoprene/teflon bearing you could use a light weight oil (such as found in a torque converter) to hold the gas in the system. On Mars or the moon its not too much of a problem because you can torque against the moon. In space its a problem if you want the shell to have zero angular momentum because as friction accumulates the shell will turn and you will constantly be needing to add thrust to stop it, so ignoring that you have a navigation system that compensates for the gyration. Also rotating space craft do not steer as non-rotating craft, so there are times when you might want friction just to kill the rotation and neutralize rotation of the shell.

While I doubt we need to apply such technology on Mars, you could test it on the Lunar surface. But, IMO, if you are continually going to be hauling people back and forth to Mars, then its better to have such a system in a interplanetary cycler that has protection from GCR and provide artificial gravity. In this case BFR is not going to be a useful thing for travel to Mars, since at most it just going to transfer passengers between 450km LEO and some equally high Martain orbit. And then they transfer again for a lander (one-way) to Mars. One option to deal with the increased mass is to send them to L1 or L2, then refuel the ships and redirect to LMO. A third option is to have a tiny device with two airlocks that only fit 2 people, they stay in the device for a few hours each day doing say 20 minutes of stress exercises. Then the device can be mounted on a spindle and spun up with ION drives or whatever. Alternatively NASA could find better solutions for dealing with space-flight, like prosthetic devices that simulate some effects of standing on the cardiovascular system. Assuming 100 days in transit, I don't see why this is a terrible problem, particularly when they get to Mars g force is only 0.39. Bottom line is if the system is going to be used in IP crew transfers, then it needs to be tested in orbit.
 

 

[kerbiloid]

Spoiler

20 hours ago, DAL59 said:

 

In principle, the scheme is ready

 

[sevenperforce]

2 hours ago, PB666 said:

Centrifuges generate alot of heat. Particularly during the initial startup. Even at martian pressures centrifuges generate alot of internal heat. In general a centrifuge would benefit from lower gravity because the stress along the vector of angular momentum is less, but having said that you can have frictionless bearings and take that out. The radius of bearings for centrifuges are intentionally made small for that reason. Within the centrifuge you have a manifold that at some point has a maximum radius (in which is a mass which conducts heat but if the bearing is small net conduction is tiny) it is at the manifold maximum radius that you have collisions at speeds from 10s of meters per second to 100s of meters per second.

The centrifuges we had in our group that were refridgerated required a magnitude more expenditure on issues dealing with vacuum pumps and refrigeration (essentially vacuum pump is part of the cooling system as it lowers the mass flow of gas around rotors)

Sorry for the confusion. The centrifuge was for fractional separation of LOX from the Martian atmosphere, not for living in.

1 hour ago, kerbiloid said:

  Hide contents

In principle, the scheme is ready

 

Hah!

[Green Baron]

39 minutes ago, sevenperforce said:

Sorry for the confusion. The centrifuge was for fractional separation of LOX from the Martian atmosphere, not for living in.

Is it possible to separate the O from the CO/CO2 with a centrifuge ?

Edit, i mean, maybe one can increase the concentration a little gravitationally ...

Also, the O will not be liquid, you'd need to cool it, and that will be difficult with a heat exchanger to cool it to -180°C or so in such a thin atmosphere. You'd probably have to dig. What other methods are there to cool something ?

Edited February 13, 2018 by Green Baron

[PB666]

36 minutes ago, Green Baron said:

Is it possible to separate the O from the CO/CO2 with a centrifuge ?

Edit, i mean, maybe one can increase the concentration a little gravitationally ...

Also, the O will not be liquid, you'd need to cool it, and that will be difficult with a heat exchanger to cool it to -180°C or so in such a thin atmosphere. You'd probably have to dig. What other methods are there to cool something ?

Lowering the temperature of CO2 and increasing the pressure gives dry ice, separates from O2. Exactly at 520 kPa (5.15 ATM) and -56.3'C Dry Ice will separate from O2.
Carbon monoxide has a triple point of 68.10 K (−205.05 °C)15.37 kPa 
Oxygen has triple point of 54.361 K (−218.79 °C), 0.1463 kPa. 
Therefore you can precipitate out CO2, the CO, leaving O2
The remaining CO in O2 can be catalyzed to CO2 and recrystallize by passing oxygen through passing through an electrified glass tube creating ozone, this will lower the combustion temperature (I believe this requires a paladium catalyst and some pressure). Or in the presence of NO can be converted with UV light to CO2 and 0_3^. NO2 can be hydrated to nitric acid and removed by reacting it with the urine waste stream and used as a fertilizer. 

 

[kerbiloid]

1 hour ago, Green Baron said:

What other methods are there to cool something ?

https://en.wikipedia.org/wiki/Turboexpander

It's big.

[Green Baron]

Cool

[DAL59]

3 hours ago, kerbiloid said:

  Hide contents

In principle, the scheme is ready

 

Fusion is not comparable to the Sabatier reaction.  The sabatier reaction has been done successfully for 100 years!

[Bill Phil]

3 hours ago, DAL59 said:

Fusion is not comparable to the Sabatier reaction.  The sabatier reaction has been done successfully for 100 years!

And we can build fusors in our garages.

[kerbiloid]

7 hours ago, DAL59 said:

The sabatier reaction has been done successfully for 100 years!

I mean that your picture represents just the common principles of the first stage of methane production.
Required purity makes the difference between "methane-rich gas" and "rocket-quality methane", especially when you have the only chance to practically test it returning from Mars.

Also do not forget that both methane and oxygen are way much more cryogenic than Mars climate, and you have to place there heavy cryostats to keep them for years.
Otherwise: Buran had special stirring tanks for LO2 to keep it for two  weeks up to one month. This is more or less how long would the lander trip last, so unlikely they can have a methane or oxygen deposit before landing.

Edited February 14, 2018 by kerbiloid

[Green Baron]

13 hours ago, PB666 said:

Lowering the temperature of CO2 and increasing the pressure gives dry ice, separates from O2. Exactly at 520 kPa (5.15 ATM) and -56.3'C Dry Ice will separate from O2.
Carbon monoxide has a triple point of 68.10 K (−205.05 °C)15.37 kPa 
Oxygen has triple point of 54.361 K (−218.79 °C), 0.1463 kPa. 
Therefore you can precipitate out CO2, the CO, leaving O2
The remaining CO in O2 can be catalyzed to CO2 and recrystallize by passing oxygen through passing through an electrified glass tube creating ozone, this will lower the combustion temperature (I believe this requires a paladium catalyst and some pressure). Or in the presence of NO can be converted with UV light to CO2 and 0_3^. NO2 can be hydrated to nitric acid and removed by reacting it with the urine waste stream and used as a fertilizer. 

 

Morning :-)

But that doesn't involve a centrifuge ? Increasing pressure would be better done with a compressor ...

 

Well, one could feed the CO2 to plants in green houses, probably easier and much more efficient in the long term and when done in large scales. And with beneficial side effects. But that is faaaar away in an uncertain future, probably needs materials and construction techniques we don't have.

 

Edited February 14, 2018 by Green Baron

[PB666]

9 hours ago, Green Baron said:

Morning :-)

But that doesn't involve a centrifuge ? Increasing pressure would be better done with a compressor ...

 

Well, one could feed the CO2 to plants in green houses, probably easier and much more efficient in the long term and when done in large scales. And with beneficial side effects. But that is faaaar away in an uncertain future, probably needs materials and construction techniques we don't have.

 

Yes I assume that greenhouse would be an alternative, but under the following circumstances.
1. A genetically engineered crop that is suited for growth under red LED [blue LED fade quickly at high intensity], at elevated biomass accumulation rates
2. the crop is specifically designed to accumulate aliphatic carbon -(CH₂)_n- (as opposed to (CHO)_n)  for example palm oil versus cellulose. More O₂
3. That some source of H2 production.
4. That access to power is infinite.

Again, something I keep repeating, these projects are doable, but feasible as a human endeavor only after sub-terrestrial architecture is in place. If the human isolation projects have shown us anything, its very difficult just to provide enough solar power on Earth to support humans, let alone grow stuff for fuel. So that metric needs to change. ISS works OK if humans are supplied with fuel and food, the second these run out the task involved in getting the ISS to create just its food is a daunting task. Greenhouses, fuel and all this stuff are on a big long IV-fluid feed going back to Earth . . . . . .So who is designing the highly efficient circulator that carries these supplies back and forth to mars (Not ISP 375 but ISP 9000)?

Pressure pumps are easier to take care of than centrifuges, and on Mars at night you can use the atmosphere as a low temperature heat sink, not efficient but you can at least produce Dry Ice. There is not enough O2 in the martian atmosphere to waste the effort on, crack the CO2 with H20 or H2 or greenhouses. I actually wouldn't worry about CO, Just find a crop that is tolerant to it and use that crop and greenhouse to remediate it. Aside from that if you have a power supply that gets you into the 'water' zone of Mars, the poles, you can pickup frozen chlatrates of dry-ice water right off the ground. 

This gets me to a peeve about some Mars logics, some of the posters are treating Mars like a gigantic invisible ocean of Water and Air. Its not, water will be hard to get, and any air you want to use for fuel or living needs to be manufactured. Its much much easier to deal with the pressures, control the temperatures and avoid the HCR-GCR when the living facility is underground, easier to stabilize the water pools.

[magnemoe]

3 hours ago, PB666 said:

This gets me to a peeve about some Mars logics, some of the posters are treating Mars like a gigantic invisible ocean of Water and Air. Its not, water will be hard to get, and any air you want to use for fuel or living needs to be manufactured. Its much much easier to deal with the pressures, control the temperatures and avoid the HCR-GCR when the living facility is underground, easier to stabilize the water pools.

We do not know how much permafrost it is on Mars, this is critical for methane production. 
Note that drilling rigs are heavy and not very automated, yes you get self loading ones, they jam far more often than self automatic guns of low quality. 
This is not an major issue on earth as you have an guy operating it, it will be an major issue for an robotic mission to Mars. 

[PB666]

Fr

25 minutes ago, magnemoe said:

We do not know how much permafrost it is on Mars, this is critical for methane production. 
Note that drilling rigs are heavy and not very automated, yes you get self loading ones, they jam far more often than self automatic guns of low quality. 
This is not an major issue on earth as you have an guy operating it, it will be an major issue for an robotic mission to Mars. 

From what I understand the expose outcrops of non-igneous material are generally less densely packed than on Earth, given the presense of large amounts of alkaline oxides its probably not that difficult to drill through them. If you could use High pressure water injection you could remove alot of the binding salts and use rather low tech techniques to debulk. There are forseable problems.

1. The outcroppings are generally not that high in elevation.
2. So you would end up having do dig down, again 10 meters at least if you want 10 meters of protection from GCR and HCR you need to excavate breccia and lose soil, then dig down into the rock, and finally dig sideways.
3. Preferable you want a tunnel 3 to 4 minimal meters in diameter, thats a pretty big tunneling device, very dense and difficult to land on Mars.

At least you need a repair station and probably some sort of ultrasonic washing station to get the fine glass off the machine, haul it into a pressurized workshop and then pressurize do that workmen could efficiently repair it safely.

[kerbiloid]

7 hours ago, magnemoe said:

Note that drilling rigs are heavy and not very automated, yes you get self loading ones, they jam far more often than self automatic guns of low quality. 

That's why that's what should be done on Mars asap.

Spoiler

 

[Kerbal7]

I can't see any realistic Colonization taking place out into the solar system unless the deep space radiation problem gets solved. From what I've read this is a show stopping hurdle that has yet to find a solution. Even a flag and footprint mission to Mars runs into this deadly problem.

[Bill Phil]

6 minutes ago, Kerbal7 said:

I can't see any realistic Colonization taking place out into the solar system unless the deep space radiation problem gets solved. From what I've read this is a show stopping hurdle that has yet to find a solution. Even a flag and footprint mission to Mars runs into this deadly problem.

Most colonization proposals have a dedicated shield for radiation. Mars and Lunar colonies generally use the local dirt to shield from radiation. Orbital colonies generally propose using large amounts of mass for shielding, sourced from asteroids/the Moon. 

Radiation shielding is mostly a matter of mass. It's a problem on flags and footprints missions due to the stringent margins and low payload mass fractions for the vehicle. Colonies won't suffer nearly so much. 

The only thing that makes it a show stopper is the sheer mass that has to be moved. For orbital colonies, this is easily 95% of the total system mass. There are ways around this by using active radiation shielding, but that needs to be developed first. Even on Mars or the Moon you need to cover your colony to shield it, unles you build underground.