# Tag Info

23

Apollo missions were on a free-return trajectory which limits your initial Lunar orbital insertion inclination close to the Earth-Moon plane. Any orbital inclination change is at that stage rather prohibitive in terms of required delta-v for the Lunar Module both on descent as well as later ascent phase to match Command Module's orbit:     &...

22

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 SpaceX or Elon Musk have made a public statement about this, the answer (IFF there is an answer at all, i.e. if they even have a plan), we simply do not know and ...

21

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 much thrust as other options out there, but it is the same fuel that ran the Space Shuttle main engine, among others. Water and carbon dioxide, easily ...

17

The total antimatter in the van Allen belts is estimated to be 160 nanograms. Annihilating that with matter would produce a whopping 8 kW-hr of energy. A quarter of a gallon of gasoline has that much energy. The star ship would be better off getting a quick spurt from a gas station pump before heading out.

16

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-earth But the deepest we can go looks like 7km What's the deepest a trench could theoretically be dug on Mars? And even if lava isn't a problem the rocks ...

14

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 reproducible throw. The catcher would also have to be a substantial structure capable of dealing with significant wear. I would use a cable car / chairlift ...

13

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 surface of Mars varies between 140K to 300K. The values for storing Methane/ Oxygen are much closer. Methane also requires less hydrogen than the LH2/LOX rocket. ...

12

This is a rather broad question, so I'll mostly try to point you in the right direction than directly answer it; First, Venusian atmosphere is highly dynamic and diverse environment both in constitution as well as ambient pressure, temperature and even weather. It forms many distinct layers at different altitudes, and its troposphere extends to about 100 km (...

11

To be somewhat more specific than @geoff that gave an overview, regarding MOXIE (Mars OXygen In situ resource utilization Experiment), according to brief notice in the NASA press release that accompanied the Mars 2020 Rover scientific payload announcement: The Mars Oxygen ISRU Experiment (MOXIE), an exploration technology investigation that will produce ...

11

To start off, literally everything can be used as rocket propellant. For a more practical approach though, water is a good resource for making hydrogen and oxygen. In the Inner solar system we have water on Mars, bound as ice on the poles, and buried just under the surface in some places. Ice on Mars Recent findings by the Clementine Lunar Orbiter ...

11

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 guidance system is going to be very, very difficult. Especially considering the lack of atmosphere which makes aerodynamic flight stability and control infeasible, ...

9

Is production of methane possible on Mars? Yes, via the Sabatier process. This has been proposed multiple times as a type of in-situ resource utilization on Mars. All that's needed is energy (e.g., sunlight), CO2, and hydrogen. The first two are easily obtainable. Except near the poles, the last is a bit of a challenge.

9

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 to the military. Part of Bellcomm's job was to participate in the selection of the Apollo landing sites. An entire issue (volume 51 number 5, 29 Mb, 176 pages) ...

9

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 on the shuttle require around 4-5 times the space of its LOX tanks, if not more. The volume and mass of the tank itself make them very difficult to deal with, ...

9

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.

8

There are several problems with this idea: Snagging the cable on a protrusion. You'd have to constantly monitor the cable to make sure it didn't snag, and/or be very careful when driving: always return along the same path you took to get somewhere. If you've ever tried to mow the lawn with an electric mower, you know how annoying this gets. Moon rock and ...

8

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 far more detail than I can, but here's a brief summary: The SHARAD (SHAllow RADar) instrument on the Mars Reconnaissance Orbiter used ground penetrating radar on ...

7

Old topic, but for those just showing up: 1) There are two leading candidates for the "unknown UV absorber" in Venus's atmosphere, and probably the most likely answer is some degree of both. One of these is elemental sulfur. The other? Ferrous chloride. Indeed, one of the Venera probes detected iron during its descent. All evidence points to there ...

7

Convective heat transfer within tenuous atmospheres wouldn't work, lunar exosphere is near vacuum, and it would be fairly limited on Mars with its average of ~ 0.6% mean sea-level Earth's atmospheric pressure, so yes, ICE blocks would have to be redesigned to either facilitate fuel and oxidizer also as a closed-loop liquid coolants (and also preheat them in ...

7

There are several issues at play here. Are the raw materials needed to be found on the moon? Can the raw materials be realistically harvested on the moon? Can the raw materials be processed into a rocket propellant on the moon? Are rocket engines which use this propellant feasible? Are there more suitable materials for this purpose to be found on the moon? ...

7

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 to have an easy time judging their height above ground and spotting obstacles, lunar landings were targeted and timed so that the Sun would be between 7 and 20 ...

7

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 the other hand, the curve might go to hell at 100%, with no light hydrogen for the heat of the burning iron to expel. Note that even at 5% H2 by weight, there ...

7

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/In_situ_resource_utilization Note that this is a fundamental part of "Mars Direct", one of the most popular ideas for a manned mission to Mars. https://en.wikipedia.org/...

6

In simplest terms: You find a chemical that is made of a mixture of oxygen and anything else, and then cause the molecules of that chemical to give up their oxygen (and thus becoming something else). 2 H₂O can be cracked into 2 H₂ + O₂ by electrolysis CO₂ can be cracked into C + O₂ by highly inefficient electrolysis, or via photosynthesis. 2 CO₂ can be ...

6

There are many proposed chemical processes that can lead to taking elements found commmonly on Mars, and using them to make more useful things for humans. The entire process is vaguely know as In Situ Resource Utilization (ISRU) That Wikipedia link nicely summarizes some of the likely approaches to be taken. There was a great Sci Fi book that looked at ...

6

I believe electrolyzing would take at least 286,000 joules per mole of water. See this Wikipedia article. A mole of water would give ~16 grams of oxygen and ~2 grams of hydrogen. So to make a million grams of propellent we'd need at least (1,000,000/18)*286,000 joules. That's about ~15,888,888,889 joules for a tonne of propellent. According to this NASA ...

6

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 made of Calcium, Titanium, and Oxygen, all of which have been found in significant quantities (>1%) on moon rocks (source). This source estimates the Moon's ...

6

Does all this make any sense? Part of it does. The idea of leaving the tanker as an orbital fuel depot in Martian orbit is OK (if you can reuse a spent upper stage for that), but it would be better to leave propellants themselves on the surface of Mars until you actually need them in orbit, to prevent propellants boil-off and risk of explosion due to ...

6

You need to make 550 liters of oxygen in 8 hours. On average in the paper provided they made about 400 milliliters of oxygen per hour (throwing out the high and low outliers). That's 3.2 liters per 8 hours. At that rate you'd need 171 times more equipment than they had for this test to make this work. They also burned through their electrodes quite often, ...

5

Martian meteorites suggest that the Martian crust has about twice as much iron as the earth's crust. Of course Mars is smaller than Earth, but most of Earth is covered in water. As a result, Mars has more available iron. Concentration is another matter, as Earth's water tends to collect iron in deposits. Still, Mars has hematite and olivine ores - it had ...

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