38 votes
Accepted

Do things get dirty in space?

Spooky This one is subjective. To some, just finding an abandoned spaceship would be spooky. I'll say there's probably not a lot that has to happen to evoke this feeling. Rusted Actually, unless ...
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  • 23.5k
28 votes

Why do CH4 (Raptor) engines produce less soot than RP-1 (Merlin) engines?

As GandalfDDI notes, you always run your engine fuel-rich so it doesn't start running engine-rich. This results in incomplete combustion of the fuel. Methane is a single carbon atom bonded to four ...
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  • 11.5k
24 votes

Why do CH4 (Raptor) engines produce less soot than RP-1 (Merlin) engines?

As explained to me (carefully and fully) by a Rocketdyne engineer you ALWAYS run rocket engines fuel rich. If you run lean the oxidizer looks at the metal parts of the engine (remember the engines are ...
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19 votes

Have light gases like hydrogen or helium been explored for ion propulsion?

(Top edit: The Question asserts "Xenon and krypton are popular despite their heavy mass" and asks about exploring H or He ion propellants for improved Isp. This answer shows that lighter is not ...
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  • 12.3k
16 votes
Accepted

Could aluminum undergo a thermite reaction with Martian dust?

Probably not any more likely than on Earth. Actually, Curiosity's (MSL) rover's wheels are made out of aluminum and they've been grinding through iron oxide rust that gives Martian regolith and the ...
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  • 75.3k
15 votes
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What is meant by 'Organics' when discussing space exploration?

'Organics' usually refer to organic compounds. From Wikipedia: http://en.wikipedia.org/wiki/Organic_compound There is no single "official" definition of an organic compound. Some textbooks ...
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  • 7,078
14 votes
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Rock flipping operation

This took a fair bit of investigation! Arm Strength The Mars Science Laboratory Robotic Arm (RA) is 2.2m in length, is made of two arm sections (an upper arm and a forearm) and is controlled by 5 ...
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  • 9,834
14 votes
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How did the kerosene-burning Black Arrow have transparent exhaust? (seems to just "hover" in photos)

Typically, kerosene-LOX engines run fuel-rich, with an oxidizer:fuel mass ratio of about 2.5:1 (as compared to 3.5:1 for complete combustion), leaving significant amounts of unburned carbon soot in ...
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12 votes
Accepted

What mitigation procedures are in place in space systems to prevent whisker growth?

Often, electrical systems prone to whisker growth are coated with a 2-3 millimeter layer of polymer (called a conformal coat); this not only prevents growth of whiskers, but also prevents any loose ...
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  • 286
12 votes

What does burnt Aerozine-50/N2O4 smell like?

No, I don't think so. Combusted hydrazine smells like ammonia, because it is ammonia, plus nitrogen and hydrogen. Unburnt hydrazine also smells like ammonia, but has a sharp sting to it that, if you ...
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  • 57.5k
11 votes

Would it be more viable to process moon rocks into Helium-3 on the Moon than doing so on Earth?

Two big ifs here. IF we achieved viable commercial fusion power (other than the sun) and IF Helium-3 was an indispensable part of this process. But for the sake of argument, let's say Helium-3 is the ...
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  • 15.1k
11 votes
Accepted

Is there a maximum Isp for "exothermic chemical reaction rockets"?

450-455s Isp is typical of H2/O2; according to the Huzel and Huang data, a hydrogen-beryllium mix combusted with oxygen can hit ~540s. The numbers in that table are for moderate chamber pressure and ...
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11 votes

Is there a maximum Isp for "exothermic chemical reaction rockets"?

The theoretical limit is set by the specific energy of the reaction of combustion of the propellant. Knowing specific energy $e$ of given substance, we can put a cap on obtainable specific impulse $...
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  • 52.4k
11 votes

How hard is the hardest ice in the solar system? Is it in Pluto's ice mountains?

1. Diamond. Its hardness is legendary. That it appears in liquid form on Uranus or Neptune hasn't been directly measured (no recent probes), but lab measurements in 2009 and 2010 of diamond's phase ...
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10 votes

What is meant by 'Organics' when discussing space exploration?

What is meant by 'Organics' when discussing space exploration? It means compounds that contain carbon, except possibly for some simple carbon compounds such as CO2, carbonates and cyanides that ...
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  • 62.9k
10 votes
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What causes the green flash during Falcon 9's ignition?

The Merlin engines are ignited with a mixture of triethylaluminium and triethylborane (TEA-TEB); according to Wikipedia: Triethylborane is strongly pyrophoric, igniting spontaneously in air, burning ...
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10 votes
Accepted

Can I make my own RP1?

I'm going to start off with a warning: if you want to get started with model rocketry, it is about a thousand times safer and easier to start with off-the-shelf solid rockets. Don't even consider ...
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10 votes

Removing perchlorate from Mars surface soil

Perchlorate contamination is a problem on Earth. Essentially, there is a series of water treatments and bioremediation, the process of using biological systems to fix the problem. Here is a detailed ...
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9 votes
Accepted

Is there salt in space?

Chlorine is a relatively rare element, so the concentrations of it is not going to be high anywhere. It is also very reactive, so all of it is likely to only occur as a part of different chemical ...
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9 votes
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What is the cause of the blue light from LH2/LOX rocket engines?

As pointed out by @Thomas, this nice thesis Radiation from High Pressure Hydrogen-Oxygen Flames and its Use in Assessing Rocket Combustion Instability - Ph. D. Thesis, Fiala, T., 2015 discusses this ...
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  • 148k
9 votes

Which scientific articles together give proof of all the chemical elements found on Mars?

From Mars Fact Sheet: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), argon (Ar), neon (Ne), krypton (Kr), xenon (Xe). From Inorganic analysis of martian surface samples at the viking landing ...
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  • 7,052
9 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.
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  • 18.9k
9 votes

How did the kerosene-burning Black Arrow have transparent exhaust? (seems to just "hover" in photos)

I think Wikipedia's Bristol Siddeley Gamma; Advantages of kerosene / peroxide engines can shed some light on the missing light. The combustion formula of kerosene and hydrogen peroxide is $$\mathrm{...
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  • 317
8 votes
Accepted

Would it be more viable to process moon rocks into Helium-3 on the Moon than doing so on Earth?

The Moon would be a much better place most likely. As you said, 220 pounds of Helium-3 in a mass of many many tons of rock, makes it so that even a few tons of equipment to be dropped on the Moon ...
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  • 118k
8 votes
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Meteor color hints at chemistry

Absolutely, it's the same as heating up metals with a blowtorch. The colour of the flame tells you what is present. Wikipedia actually has a handy list giving an indication of the significant elements ...
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  • 13.4k
8 votes

Removing perchlorate from Mars surface soil

Apart from perchlorate treatment mentioned in @Chris's answer, there are some other methods which could be able to remove the perchlorate from the martian soil: Rinsing the soil with water. ...
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8 votes

Are rocket fuels and LOX pure or are there additives?

Non-hypergolic liquid fuels i.e.: LH2, LOX, Methane etc are all kept as pure as possible. One of the major advantages of these is that they burn clean. Any additions are potentially problematic: ...
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  • 3,382
7 votes

What mitigation procedures are in place in space systems to prevent whisker growth?

Conformal coatings mostly, just like on Earth. A thin polymer layer impedes problematic whiskers principally by confining them to the inside of the coating. Theses links confirm that NASA has a large ...
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  • 2,131
7 votes

What is required to produce rocket quality methane fuel and oxygen from Mars' atmosphere?

That is the beauty of rocket engines, you can put almost whatever you want into them, and they still kinda work. (That said, I see that as beauty, engineers just scream in terror.) Joking aside, ...
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7 votes

What limits burning speed of solid propellant?

If we have a pressure shock front travelling very fast through the material it is an explosion. The reaction inside the explosive is started by the sudden pressure rise, not by a temperature rise. But ...
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