Skip to main content
39 votes
Accepted

Ultimate fate of rocket propellant in space?

Presumably you are asking about engines that are used once a space vehicle has escaped the Earth's gravitational sphere of influence, or is close to that point. Rocket exhaust during launch becomes a ...
David Hammen's user avatar
23 votes

How does SpaceX plan to supply or recycle respiratory gasses?

How does SpaceX plan to supply or recycle respiratory gasses? As with most questions about SpaceX, the answer to this question is essentially that SpaceX is a private company, and unless either ...
Jörg W Mittag's user avatar
21 votes
Accepted

Can a rocket refuel on Mars from water?

It absolutely could! First of all, water can be split in to hydrogen and oxygen, which can be enough to launch a rocket. Hydrogen requires a very low temperature, and the rocket engine doesn't have as ...
PearsonArtPhoto's user avatar
  • 121k
17 votes
Accepted

Would a sufficiently deep cavern on Mars provide habitable temperature and atmospheric pressure? Was Dick Tracy wrong?

Looks like it's not possible: To get Earth-normal pressure we need 55km https://astronomy.stackexchange.com/questions/14871/at-what-depth-on-mars-would-the-atmosphere-have-equal-pressure-of-that-on-...
Loren Pechtel's user avatar
14 votes

Has trebuchet-based materials transport on the Moon been researched before?

It’s an interesting idea, but the problem will be accuracy. Depending on the conditions found on the ground, it might be difficult to produce uniform “ammunition” and an “engine” with a sufficiently ...
Slarty's user avatar
  • 9,560
13 votes
Accepted

Making propellants on Mars: Why not just LH2/LOX instead of methane?

Liquid Hydrogen is difficult to deal with. The temperature must be 33 K or lower. Liquid Oxygen requires 90K, and Liquid Methane is similar. The temperature requirements are far less as such. The ...
PearsonArtPhoto's user avatar
  • 121k
13 votes

Ultimate fate of rocket propellant in space?

No need to theorize. Astronomers have studied this problem for centuries, as there are natural objects that emit conspicuous plumes of rocket exhaust. We call them comets. The exhaust forms two "...
John Doty's user avatar
  • 3,364
12 votes

Most attractive resource on the Moon

First off almost all resource extraction in space is really only remotely close to cost effective if the resources themselves are used in space. The general number thrown around is ~$10,000 per ...
Josh King's user avatar
  • 2,429
11 votes

Has trebuchet-based materials transport on the Moon been researched before?

I'm not sure if a thrower-catcher system is a good solution. Some points: Getting a canon (or launcher of any sort) to fire accurately across four kilometers without precision machined shots or a ...
Dragongeek's user avatar
  • 19.1k
10 votes
Accepted

Sabatier reaction oxygen to methane ratio for Mars ascent propellant

It's a 4:1 ratio by mass. One molecule of methane masses 16 daltons, whereas one of dioxygen ($O_2$) masses 32, so two molecules of oxygen massed four times as as much as one of methane.
Steve Linton's user avatar
  • 19.6k
9 votes

Making propellants on Mars: Why not just LH2/LOX instead of methane?

As briefly mentioned in the previous answer, H2 is very tricky to deal with. The temperature is one thing, but what he didn't mention was its extremely low density. If I recall correctly the LH2 tanks ...
UIDAlexD's user avatar
  • 1,108
9 votes

Why didn't Apollo land on the Lunar poles?

The Apollo program contracted Bellcomm (a joint venture of AT&T Bell Labs and Western Electric) as technical advisors. It played a similar advisory role that the RAND Corporation often provided ...
DrSheldon's user avatar
  • 48k
8 votes
Accepted

What's the scientific evidence of water for return trip methalox on Mars?

There is an interesting podcast that I listen to - We Martians. Last Nov they had an episode that touches heavily on this. The episode is here: http://www.wemartians.com/home/015 and it goes into ...
jgalak's user avatar
  • 766
7 votes

Why didn't Apollo land on the Lunar poles?

Assuming the counterfactual situation that NASA knew (or expected) that there would be ice in the polar craters, the reason NASA wouldn't do a polar Apollo landing is lighting. In order for the crew ...
Mark's user avatar
  • 15.3k
7 votes
Accepted

How much land does a colony on Mars need to start off?

Of these, the only one that isn't well known is nitrogen. The nitrogen levels at Mars are somewhat unknown, but expected to be pretty low overall. Of course, nitrogen isn't required for a colony of ...
PearsonArtPhoto's user avatar
  • 121k
7 votes
Accepted

What specific impulse can I expect from iron powder produced from lunar regolith?

Figure 5 on page 23 of this paper shows the Isp of tri-propellants including iron, where the curve goes out to 95% Fe and 5% H2. Just eyeballing it, the curves might converge at around 190 seconds. On ...
Mark Adler's user avatar
  • 58.2k
7 votes

Can a rocket refuel on Mars from water?

Have a look at the wikipedia article for "In situ resource utilization". This is exactly what you're talking about, creating fuel on another planetary body. https://en.wikipedia.org/wiki/...
Freddie R's user avatar
  • 2,544
6 votes
Accepted

Manufacturing solar cells on the Moon

Perovskites may prevent the need for such complex manufacturing facilities. https://www.nasa.gov/feature/glenn/2019/building-solar-panels-in-space-might-be-as-easy-as-clicking-print Perovskites are ...
DJG's user avatar
  • 804
6 votes

Sabatier reaction oxygen to methane ratio for Mars ascent propellant

In practice, what you do is actually you start out with water to generate the $\mathrm{H_2}$, rather than just electrolysing the water that comes out of the Sabatier reaction. (Well, you'd probably do ...
leftaroundabout's user avatar
5 votes

Mining lunar thorium for building nuclear rockets on the Moon

Mining lunar thorium gains you nothing. Thorium is not fissile and cannot be used to fuel a nuclear rocket, power plant, or RTG. Designs for "Thorium" nuclear power plants use thorium as a fertile ...
Kengineer's user avatar
  • 1,748
5 votes

Are there proper ore bodies in Mars' crust?

It is not a given that all lunar meteorites are as scattered as the impactor of Barringer crater. Some meteorites strike as slowly as 3 to 4 km/s. And magnetic anomalies suggest rich metal deposits ...
HopDavid's user avatar
  • 15.8k
5 votes

Is Mars iron too oxidized to pick up with a magnet?

No, at least some of it will stick to a magnet. Here is an image of dust on the capture and filter magnets on the Opportunity rover on Mars.
Mark Adler's user avatar
  • 58.2k
5 votes
Accepted

How much equipment will be required to mine 600 tons of water ice on Mars?

Unknown This is very, very mission dependent. Where does it land? How long do they stay? What is the mission hoping to accomplish, beyond producing enough fuel to return? Add in all the other unknowns ...
codeMonkey's user avatar
  • 1,713
4 votes

Mining construction materials and other resources on Mars

You can make a kind of concrete from sulphur, although the idea of living in buildings made of a potentially poisonous material might not sound very attractive. There is also water which should ...
choeger's user avatar
  • 2,453
4 votes

Why didn't Apollo land on the Lunar poles?

If we go after lunar pole, there is one more subtlety. NASA reports that most of the known ice aroubd the South Pole, with only sparse distribution at the North Pole. The South Pole and its ...
Oscar Lanzi's user avatar
  • 8,525
4 votes

Manufacturing solar cells on the Moon

Lunar Reources Inc. proposes to manufacture solar panels in situ by electrolyzing the lunar regolith to seperate the various components (metals, silicon, oxygen, etc.) and vacuum-depositing material ...
f_n_lyre's user avatar
  • 101
4 votes

Methane internal combustion engines for rovers on Mars and Moon. Feasibility?

We only need to generate electricity. Even here on Earth, it is sometimes more practical to use the internal combustion engine to generate electricity and drive the wheels using electric motors than ...
Dean White's user avatar
4 votes

How much fuel is being consumed by all spacecrafts in orbit?

BOE: 1000 active satellites, launched with 3 tons of fuel+oxidizer each for an expected lifetime of 15 years is 3000/15=200 tons of fuel+oxidizer needed per year. Note: 3 tons is too much, as many ...
Hobbes's user avatar
  • 128k
4 votes

How to size Solar Array for Mars Surface

It is usually easier to first determine the energy required by your system. You have done that already - assuming that the ISRU plant needs to continuously operate at 10.1 kW per sol: $$ 10.1 \ [kW] * ...
Armadillo's user avatar
  • 1,426
4 votes

Most attractive resource on the Moon

Lunar ice may be of some importance for a different reason: its possible role in making iron and steel. On Earth, we commonly use carbon (coke) to smelt iron from its oxides, thus to make steel. But ...
Oscar Lanzi's user avatar
  • 8,525

Only top scored, non community-wiki answers of a minimum length are eligible