37
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 ...
- 23.8k
33
votes
Accepted
Why are nitric acid and hydrogen combinations not used as rocket fuel?
"Kilojoules per mole" is not the most important measure of a rocket fuel's effectiveness. The most important is effective exhaust velocity, often expressed as "specific impulse".
...
- 15.4k
28
votes
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 ...
- 15.4k
25
votes
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 ...
- 923
21
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 ...
- 12.7k
14
votes
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 ...
- 9,966
14
votes
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 ...
- 170k
12
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 $...
- 55.1k
12
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 ...
- 170k
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 ...
- 286
12
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 ...
- 12.2k
12
votes
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 ...
12
votes
Why are nitric acid and hydrogen combinations not used as rocket fuel?
The "why not this combination" answer: in Ignition! it's mentioned that the main drive for using RFNA as a propellant is that it's an oxidizer that's liquid at outdoor temperatures (say, -40 ...
- 605
11
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 ...
- 2,267
11
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 ...
- 7,535
10
votes
Accepted
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 ...
- 170k
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 ...
- 170k
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.
- 19.6k
9
votes
Accepted
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 ...
- 149k
9
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. ...
- 1,022
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{...
- 327
8
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 ...
- 1,714
8
votes
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 ...
- 13.6k
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: ...
- 3,442
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 ...
- 2,157
7
votes
What is the process to produce a chemical composition spectrum of a celestial body?
The spectrum you show from Titan was taken using the IRIS spectrometer aboard Voyager 1. Of course Voyager 2 had one as well. A huge amount of work went into developing and optimizing the design in ...
- 149k
7
votes
Accepted
What would a "water" landing on Titan be like? How viscous is the liquid?
According to NASA's article "Rainbows on Titan":
The density of liquid methane is only about half the density of water. This is something, say, a boat builder on Titan would need to take ...
- 170k
7
votes
What are the energy-to-mass ratios of some fuels/oxidizers, when including the oxidizer?
First we have to go back to the chemical equations, and this time, include the standard enthalpy of combustion.
Hydrogen: 2 H$_2$ + O$_2$ → 2 H$_2$O + 572 kJ/mol
Methane: CH$_4$ + 2 O$_2$ → CO$_2$ + ...
- 4,596
7
votes
Accepted
Sources of Xenon or other noble gases in space?
Xenon can be found elsewhere. Wikipedia's Xenon; occurrence and production mentions a relatively high abundance of xenon on Jupiter, which is actually unexplained. But xenon is overall among the ...
- 8,525
7
votes
Are there any gaseous monopropellants?
All rocket propellants end up in the gas phase and are stored in the liquid or solid phases aboard rockets. Many propellants could easily be stored in the gas phase aboard a rocket, but they are not ...
- 9,802
Only top scored, non community-wiki answers of a minimum length are eligible