# Tag Info

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 ...
• 23.7k

### Why do $\text{CH}_4$ (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 ...
• 11.7k

### Why do $\text{CH}_4$ (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 ...
• 733

### 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 ...
• 12.4k
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 ...
• 75.7k
Accepted

### 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 ...
• 7,089
Accepted

### 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 ...
• 9,854
Accepted

### 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 ...
• 162k
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 ...
• 286

### 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 ...
• 57.9k

### Can the higher oxides of nitrogen, like nitrogen pentoxide, be used as oxidisers in rocket engines?

Not likely N2O5 Well, the stuff IS a very strong oxidizer. But considering that the solid form is a hard white salt-like substance, and it melts at 41 °C, and boils at 47 °C, so it can be a wee bit ...

### 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 ...
• 15.2k
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 ...
• 162k

• 317
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 ...
• 119k
Accepted

### What are the odds of finding a lifeless planet with breathable air?

It's actually not that far-fetched, but non-biological processes involved with creation of such breathable atmospheres likely wouldn't be sustainable for a very long time. Let's imagine a largely ...
• 75.7k

### 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 ...
• 1,704
Accepted

### 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 ...
• 13.5k