Colonization Discussion Thread (split from SpaceX)

[Wjolcz]

11 minutes ago, kerbiloid said:

Why at all that methane?
Martian atmosphere contains 6% of nitrogen to make ammonia.
Ammonia is liquid at -70..-30°C, so during almost full Martian day (-100..+30°C) with lesser effort than methane's -160°С. It's easier to store it.
It's a well-known rocket fuel. Ammolox ISP*g ~3200 m/s.
It can be easily combined with hydrogen to make an ammohydrolox engine (as Martian atmosphere is puny, so hydrogen has high ISP even at surface).
It's useful to produce and store UDMH, NTO, hydrazine hydrate.
It doesn't crap pipes and tubes. You can easily convert it into different things.

Methanol (can be produced out of the same CO2 and H2O) + hydrazinehydrate+ water is C-Stoff. Together with HTP it's a famous German jets propellant from WWII.
It's a natural cheap fuel for drills and other high-power plants without carrying reactor  on your rover.

Methane is not needed.

6% is not much though. How much time does it take to make ammonia and how much time does it take to make methane?

Besides, isn't methane easier to make anyway?

[kerbiloid]

8 minutes ago, Wjolcz said:

How much time does it take to make ammonia and how much time does it take to make methane?

Besides, isn't methane easier to make anyway?

Methane. CO2 + 4H2 → CH4 + 2H2O + remains of CO2 + parasite CO, then keep it at -160 permanently cooling at replacing the boil-off losses.
Ammonia. N2 + 3H2 → 2 NH3. Insulate the tank. You can use the NH3 itself as a cooling agent, not so cryogenic like methane. Density is 730 (A) vs 660 (M) kg/m³.

Edited June 16, 2018 by kerbiloid

[ment18]

4 hours ago, kerbiloid said:

Why at all that methane?
Martian atmosphere contains 6% of nitrogen to make ammonia.
Ammonia is liquid at -70..-30°C, so during almost full Martian day (-100..+30°C) with lesser effort than methane's -160°С. It's easier to store it.
It's a well-known rocket fuel. Ammolox ISP*g ~3200 m/s.
It can be easily combined with hydrogen to make an ammohydrolox engine (as Martian atmosphere is puny, so hydrogen has high ISP even at surface).
It's useful to produce and store UDMH, NTO, hydrazine hydrate.
It doesn't crap pipes and tubes. You can easily convert it into different things.

Methanol (can be produced out of the same CO2 and H2O) + hydrazinehydrate+ water is C-Stoff. Together with HTP it's a famous German jets propellant from WWII.
It's a natural cheap fuel for drills and other high-power plants without carrying reactor  on your rover.

Methane is not needed.

 

4 hours ago, kerbiloid said:

Methane. CO2 + 4H2 → CH4 + 2H2O + remains of CO2 + parasite CO, then keep it at -160 permanently cooling at replacing the boil-off losses.
Ammonia. N2 + 3H2 → 2 NH3. Insulate the tank. You can use the NH3 itself as a cooling agent, not so cryogenic like methane. Density is 730 (A) vs 660 (M) kg/m³.

-Martian Atmosphere 95% CO2, its super thin to begin with

-Methane and LOX have very similar temp ranges (methane freezes at -182 and LOX boils at -183, tanks do not need to be badly insulated from each other.)  They already have to be cryogenic for LOX

-Better ISP, I can't find good number but Methalox is probably 20 or 30s better then ammolox.

-Not using hydrogen in long duration spaceflight, tri-propellant engines are not easy.

-Can ammonia do autogenous pressurization?

-Why would you want hydrazine.  The point is to have as few propellants as possible.  Make everything simple.

-It just has lower performance.  WW2 jet propellants are garbage specific impulse.  Everything is super mass limited, need maximum mass efficiency from propellant.

-Methane cars exists, it is easy rover fuel, a specific CO/O2 engine would far outperform any other propellant combo on Mars surface.  Nobody even cares about reactors on rovers between fuel cells and batteries.

-Already have to do electrolysis to get hydrogen, the water is easily dealt with.

Edited June 16, 2018 by ment18

[kerbiloid]

1 hour ago, ment18 said:

Martian Atmosphere 95% CO2

Yes, my fault, nitrogen is ~3%.

1 hour ago, ment18 said:

-Methane and LOX have very similar temp ranges (methane freezes at -182 and LOX boils at -183, tanks do not need to be badly insulated from each other.)  They already have to be cryogenic for LOX

And it's hard to store both, as their boiling point is far below the Martian -100°C night temperature.
While ammonia has an intermediate temperature between LOX and Mars, and it's almost always inside/near the liquid temperature range.
It's itself like an insulation and cooling agent at once.

To make methane you have to electrolyze water.
Then you store the oxygen and use hydrogen to reduce carbon dioxide. Then you have to purify the resulting gas mixture.
This 1) causes the hydrogen losses; 2) decreases the fuel processing rate compared to oxidizer. So, you always have a disbalance of fuel:oxidizer ratio until both tanks are full.
Then you have to hold two highly cryogenic liquids continously producing both of them to recover the losses.
So, keeping this process running for months, you would mostly be venting the product out. Or spend a lot of energy cooling the tank.

Ammonia is not so cryogenic, it's easier to store it for long time.
So, you can first produce fuel, storing as much oxygen as appears, but not paying much attention on it. Then if necessary produce more oxygen to recover its loss.

Nitrogen can be easily separated from the Martian atmosphere, as its boiling point differs a lot from carbon dioxide (unlike the Earth air, where N and O have almost similar temperature.).
Getting pure nitrogen and pure electrolytic hydrogen, you can simplify the purifying procedure, as don't need to separate a bunch of carbon compounds.
In fact on Mars you get the last phase of ammonia producing on Earth, when already purified nitrogen and hydrogen get pumped into the reactor.
 

1 hour ago, ment18 said:

Better ISP, I can't find good number but Methalox is probably 20 or 30s better then ammolox.

Better density. 730 vs 660.
Also combining with hydrogen, you can vary thrust and ISP, selecting optimal ratio. Density anyway stays better.
Lighter tank insulation, as less cryogenic. Mars for liquid ammonia is a "room temperature".
Lighter cooling system for the same reason.

1 hour ago, ment18 said:

Can ammonia do autogenous pressurization?

Don't know, should search.

1 hour ago, ment18 said:

Not using hydrogen in long duration spaceflight, tri-propellant engines are not easy.

In long-duration spaceflight it's easier to store ammonia, unless you cross the asteroid belt.
Again, lesser ISP, but lighter tanks and cooling system.

1 hour ago, ment18 said:

Why would you want hydrazine.  The point is to have as few propellants as possible.  Make everything simple.

Because hydrazines have enough high ISP and arer very storable. ICBM are fueled for tens years with no problems.
"As few propellants as possib;e" keyword is "as possible". After getting to Mars you have to operate on it, otherwise why to fly.

Hydrazines allow to:

• have a ready to launch ship to evacuate
• have hoppers/fliers to fly here and there, delivering people and rovers (look at the Martian rover wheels after 40 km of slow walk, don't forget, it's abrasive chemically active crap instead of ground)
• have more heavy quadrocopters than with a single webcam.
• produce fuel as slow as required, as the fuel doesn't boil off. You can make a kilogram per day and still have a tonne 1000 days later.
• they are not cryogenic, you can drop a barrel in a camp, and it will be still there a year later (well, maybe not so literally, as you have to heat it, but a little heater is much easier than a big cooler);
  recall the  Antarctic expeditions: they would never reach the pole if they couldn't make a chain of magazines along the route.
• RCS needs fuel, and methalox is not the best choice for it, while hydrazines are
• methanol can be produced from the same CO2 and H2 as methane, it's non-cryogenic storable; together with hydrazine hydrate (requires ammonia to be produced) it's a cheaper and less toxic alternative than pure UDMH, you can make a lot of it and easily store;

You can use ammonia to produce several storable types of dense and hypergolic rocket fuel.
With methane you anyway won't be making kerosene or plastic.
Methane is just a poorly storable fuel. Ammonia was used , though has better alternatives on Earth, so irl used in tests only. Methane still never used in real rockets except modern (also still test) designs.

As well as a fuel for ground devices and explosives (astrolite) for geological needs and rock shaping.

1 hour ago, ment18 said:

It just has lower performance.  WW2 jet propellants are garbage specific impulse.

That's exactly why I've mentioned it not as a rocket propellant, but as a cheap fuel for ground devices having a forced mode.

Solar panels on roof for easy riding. a magnetohydrodynamic generator or so for the forced mode (drilling/pushing/pullling/bulldozing/etc).
Unless you are going to cover hectares of ground with portable solar panels and repeat this every 500 m while working.
Unless you want to have a portable reactor on your rover to power the drill.
(Don't forget, you are doing this in 20 km from base, so can't have electric cables from there).

Fuel cells usually give watts-kilowatts. A typical drill has a power of a tank engine, up to MW.
No cells, no panels are even close. Either a rocket engine, or a nuclear plant.

Btw, this is also a solution to "how to broom the territory after a sandstorm".
Like in an airport. Have a C-Stoff fueled rocket engine on a rover and use it as a vacuum cleaner, together with carbon dioxide pump. Just on Earth you do this with kerosene.

1 hour ago, ment18 said:

Methane cars exists

Earth air does not. This is Mars, any air you have to have in a tank.

Edited June 16, 2018 by kerbiloid

[AVaughan]

6 hours ago, Wjolcz said:

Ammolox ISP*g ~3200 m/s.

So that would mean that an Ammolox engine would have around 320 ISP?  According to wikipedia the Methane/Lox vacuum engine SpaceX is developing has a vacuum ISP of 375.  So even is Ammolox is easier to make and store, Methane/Lox is a more efficient rocket fuel.  

[Mad Rocket Scientist]

I think methane was chosen because carbon, hydrogen, and oxygen are readily available almost everywhere in the solar system, while ammonia is relatively rare.

Edited June 16, 2018 by Mad Rocket Scientist

[Wjolcz]

4 minutes ago, Mad Rocket Scientist said:

I think methane was chosen because carbon, hydrogen, and oxygen are readily available almost everywhere in the solar system, while ammonia is relatively rare.

I have the same feeling. Not sure from where you would get carbon on Europa though.

[IncongruousGoat]

1 hour ago, Wjolcz said:

I have the same feeling. Not sure from where you would get carbon on Europa though.

Or the Moon, for that matter. In-situ methane synthesis is only really practicable on Earth (duh), on Mars, in the asteroid belt (carbonaceous chondrites provide everything you need), and on Titan. For now, though, Musk only cares about Mars, and methane synthesis makes sense for Mars. Colonization efforts directed at other bodies will almost certainly use a different, and presumably more sophisticated, transport infrastructure. Who knows, by then we might have enough infrastructure in place to permit fully non-atmospheric transfer craft. Now that would be something.

[StrandedonEarth]

Methane doesn't have to be refrigerated to be a liquid; it can also be stored as a liquid under high pressure (see LNG tankers). Yes, that requires heavier tanks, but thinner tanks can be buried to provide more strength. Also, since Mars is colder than Earth, the vapor pressure of methane will be lower. The methane can then be refrigerated to load into the BFS

[Ultimate Steve]

5 hours ago, IncongruousGoat said:

Or the Moon, for that matter. In-situ methane synthesis is only really practicable on Earth (duh), on Mars, in the asteroid belt (carbonaceous chondrites provide everything you need), and on Titan. For now, though, Musk only cares about Mars, and methane synthesis makes sense for Mars. Colonization efforts directed at other bodies will almost certainly use a different, and presumably more sophisticated, transport infrastructure. Who knows, by then we might have enough infrastructure in place to permit fully non-atmospheric transfer craft. Now that would be something.

This makes me a bit more hyped for the day when nuclear rockets come into widespread use - you can use literally almost any liquid as a reaction mass and you can basically refuel anywhere you want.

[zolotiyeruki]

15 minutes ago, StrandedonEarth said:

Methane doesn't have to be refrigerated to be a liquid; it can also be stored as a liquid under high pressure (see LNG tankers). Yes, that requires heavier tanks, but thinner tanks can be buried to provide more strength. Also, since Mars is colder than Earth, the vapor pressure of methane will be lower. The methane can then be refrigerated to load into the BFS

Actually, LNG tankers ship refrigerated methane at atmospheric pressure.  The size of the ships means that the ratio of surface area to total volume is pretty low, so the losses to evaporation are pretty small.  That boil-off gas doesn't have to be vented or flared, either--they can use it in the ship's engines.

[StrandedonEarth]

21 minutes ago, zolotiyeruki said:

Actually, LNG tankers ship refrigerated methane at atmospheric pressure.  The size of the ships means that the ratio of surface area to total volume is pretty low, so the losses to evaporation are pretty small.  That boil-off gas doesn't have to be vented or flared, either--they can use it in the ship's engines.

I stand corrected

[IncongruousGoat]

59 minutes ago, Ultimate Steve said:

This makes me a bit more hyped for the day when nuclear rockets come into widespread use - you can use literally almost any liquid as a reaction mass and you can basically refuel anywhere you want.

Well, I wouldn't go quite that far. You could very easily run into heating and plumbing problems if, say, you tried to feed ammonia into an engine designed to take hydrogen. It might (in principle) be possible to design an engine that could take anything that will flow as a propellant, but the cooling and pump mechanisms would have to operate on a separate cycle from the fuel (so no turbopumps or regenerative cooling), and engineering such a thing would be tricky, to say the least. Not impossible, but not trivial either.

[LordFerret]

In the news today:
Apparently retired Canadian astronaut Chris Hadfield feels that neither Space-X nor NASA nor Blue Origin spacecraft will ever make it to Mars, as things stand today. Why? 'Because the safety risks are too great.' I think he might be right; So far, all we've seen is a publicity stunt... save probes and rovers.

Note: The video(s) with both of these articles is either blocked or removed or suppressed or ... you get (don't get) the picture.

This Retired Astronaut Says SpaceX and NASA Rockets 'Will Never Go to Mars'

Retired Astronaut Believes That NASA, SpaceX And Blue Origin Rockets Could Not Transport Humans To Mars

[NSEP]

7 minutes ago, LordFerret said:

In the news today:
Apparently retired Canadian astronaut Chris Hadfield feels that neither Space-X nor NASA nor Blue Origin spacecraft will ever make it to Mars, as things stand today. Why? 'Because the safety risks are too great.' I think he might be right; So far, all we've seen is a publicity stunt... save probes and rovers.

Note: The video(s) with both of these articles is either blocked or removed or suppressed or ... you get (don't get) the picture.

This Retired Astronaut Says SpaceX and NASA Rockets 'Will Never Go to Mars'

Retired Astronaut Believes That NASA, SpaceX And Blue Origin Rockets Could Not Transport Humans To Mars

Videos don't work for me too.

So bassicly what he is saying is that chemical propulsion is too risky for interplanetary travel? Makes sense, actually, but i think we will have to see. If both cargo BFSpaceships explode during their transfer to Mars, we will have our answer.

[StrandedonEarth]

Sometimes I think society has gotten too risk-averse (especially given the perception of overpopulation), which will paralyze human space exploration and colonization. 

If someone wants to go to the Moon or Mars, have them sign a waiver acknowledging that it may be a one-way trip (if they get there at all) and light that candle!

Edited June 18, 2018 by StrandedonEarth

[sevenperforce]

30 minutes ago, StrandedonEarth said:

Sometimes I think society has gotten too risk-averse (especially given the perception of overpopulation), which will paralyze human space exploration and colonization. 

If someone wants to go to the Moon or Mars, have them sign a waiver acknowledging that it may be a one-way trip (if they get there at all) and light that candle!

I know Chris is an STS guy, but good grief, I'd sure as hell rather ride a Falcon or BFR to Mars than strap into the Shuttle.

We need to think of going to Mars like we did during Mercury and Apollo, not in terms of Skylab and riding Soyuz to the ISS.

[ment18]

Its ridiculous how society is willing to accept thousands of deaths in many areas, but none in space travel.  

[Bill Phil]

1 hour ago, ment18 said:

Its ridiculous how society is willing to accept thousands of deaths in many areas, but none in space travel.  

Publicity. 

A space mission will be highly publicized. Tens of thousands of deaths in car accidents is something local news handles on an individual  basis (and barely), not global news.

That's the underlying issue. Any deaths in a major space mission will be highly publicized. See Challenger, Columbia, and the high risk of losing Apollo 13. This then leads to the program suffering even more than just losing people. 

Same with nuclear reactors. The risks and consequences of improper management are highly publicized. Safe operation isn't news worthy. Meanwhile we have major industries and systems that cause thousands of deaths when operating exactly as designed.

Edited June 18, 2018 by Bill Phil

[wumpus]

20 minutes ago, Bill Phil said:

Publicity. 

A space mission will be highly publicized. Tens of thousands of deaths in car accidents is something local news handles on an individual  basis (and barely), not global news.

That's the underlying issue. Any deaths in a major space mission will be highly publicized. See Challenger, Columbia, and the high risk of losing Apollo 13. This then leads to the program suffering even more than just losing people. 

Same with nuclear reactors. The risks and consequences of improper management are highly publicized. Safe operation isn't news worthy. Meanwhile we have major industries and systems that cause thousands of deaths when operating exactly as designed.

I'd say the issue is more like driving vs. flying.  The drive to the airport and back might be the biggest danger you face while flying on a commercial airliner, but people are convinced that they are dangerous because they see every crash on the news.

- Basically anything on the news isn't a danger, otherwise it wouldn't be "news" it would be "business as usual".  PS: crime peaked in the US around 1980 and has steadily gone down since, but they keep selling it as "more dangerous than before".

[Bill Phil]

9 minutes ago, wumpus said:

I'd say the issue is more like driving vs. flying.  The drive to the airport and back might be the biggest danger you face while flying on a commercial airliner, but people are convinced that they are dangerous because they see every crash on the news.

- Basically anything on the news isn't a danger, otherwise it wouldn't be "news" it would be "business as usual".  PS: crime peaked in the US around 1980 and has steadily gone down since, but they keep selling it as "more dangerous than before".

Yeah. And there was one year where the news reported loads about shark attacks but shark attacks weren't very high that year.

Ratings.

[NSEP]

Dying on my way to Mars is the best way to die to be honest. Sacrificing yourself for the future. Cool!

Im not afraid of death in general, im afraid of dying for no good reason.

Okay, this is getting a little too dark.

[sh1pman]

6 minutes ago, NSEP said:

 

 Dying on my way to Mars is the best way to die to be honest. Sacrificing yourself for the future. Cool!

 

Your family may think otherwise. They’ll want you to return back home safely. Can you tell your wife and children that you're going on a suicide mission, and there’s a good chance you’ll die (for science and progress)? I don’t think I can.

[NSEP]

7 minutes ago, sh1pman said:

Your family may think otherwise. They’ll want you to return back home safely. Can you tell your wife and children that you're going on a suicide mission, and there’s a good chance you’ll die (for science and progress)? I don’t think I can.

Heck, i might just not have a wife and kids at all to begin with.

Im ending it here, its getting off-topic and wayyyy too much in the sensitve zone.

[IncongruousGoat]

1 hour ago, Bill Phil said:

Yeah. And there was one year where the news reported loads about shark attacks but shark attacks weren't very high that year.

Ratings.

But reporting by general media won't really matter, especially in the beginning. There are more than enough people in the world do understand the technology and the risks, and who will be willing to make the journey regardless. Remember, we don't need to get everyone to think it's safe, or even most people. Just enough people to start the colony going. It's not like buying a one-way ticket to Mars is illegal, especially if SpaceX are operating their own launch site and range. In any case, SpaceX will be highly motivated to make the trip as safe as possible, so I don't see this becoming a problem in the first place. Additionally, humans have shown the ability to fix things if stuff starts breaking - case in point, Apollo 13. As long as SpaceX builds a modicum of redundancy into the BFS (which they seem to be doing), things should be just fine. Space travel is hard, but by no means impossible, and engineers have proven really, really good at doing hard things.

Edited June 18, 2018 by IncongruousGoat