34
votes
Accepted
Do spacecraft ever release unneeded gases into space?
You bet. Not only gases, but astronaut pee as well! Which could result in spectacular light shows.
This happens for several reasons:
Spacecraft and the tanks inside them are built to be as light as ...
- 189k
31
votes
Accepted
Do liquid propellant rocket engines experience thrust oscillation?
Yes, in liquid engines this phenomenon is called "rough combustion".
Sutton (4th edition) says
Combustion that gives pressure fluctuations greater than about +/- 5%
of the mean pressure at a ...
- 189k
30
votes
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Were the Space Shuttle's Main Engines ever off while the Solid Rocket Boosters were firing?
Hydrogen-oxygen engines produce a relatively faint blue flame, with visible blue-white shock discs or diamonds under certain circumstances, particularly low altitudes where air pressure confines the ...
- 172k
27
votes
Were the Space Shuttle's Main Engines ever off while the Solid Rocket Boosters were firing?
No, they were never off. Here is my explanation:
have you ever noticed that the top engine is tilted down? This is us to keep the center of thrust more or less aligned with center of mass of the ...
- 2,060
22
votes
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Could rocket exhaust eventually lead to detrimental effects from interplanetary space pollution?
No, this isn't an issue. Space is big, and the exhaust gases rapidly disperse, eventually merging with the solar wind. Exhaust can produce some solids, eg carbon, but these particles are microscopic ...
- 3,300
21
votes
Apollo 4 vs Apollo 8 plume
In addition to the foreshortening illustrated by Organic Marble, the appearance of rocket plumes changes significantly with altitude. At higher altitudes, the pressure of the surrounding air is lower, ...
- 172k
19
votes
Could rocket exhaust eventually lead to detrimental effects from interplanetary space pollution?
The total mass of the (natural) interplanetary dust cloud is approximately $3.5×10^{16}$ kg. That's 7 billion Starship launchers. There is no conceivable way for humans to add significantly to ...
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15
votes
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Is it possible to create different colors in rocket exhaust?
Sure, it's entirely possible. Not unusual in model rocketry (where style points can count for something), for example:
- 1,299
15
votes
Why should the velocity through the nozzle throat be sonic?
Uwe's comment on the question is spot on. The characteristics of the flow through the nozzle depend critically on the pressure ratio - the two pressures being the pressure at the entrance to and exit ...
- 189k
14
votes
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Why does Merlin 1D Vac turbopump drive exhaust go around the nozzle?
The turbopump exhaust in the Merlin 1D vacuum versions is directed into the nozzle where it acts as a cooling layer between the very hot chamber exhaust and the wall of the nozzle extension. The ...
- 172k
14
votes
Do liquid propellant rocket engines experience thrust oscillation?
In addition to the "rough combustion" that Organic Marble mentions, liquid engines also characteristically suffer from pogo oscillation. This is the phenomenon in which the thrust causes acceleration ...
- 6,823
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 ...
- 172k
10
votes
Were the Space Shuttle's Main Engines ever off while the Solid Rocket Boosters were firing?
Offered as a supplement to the other answers - here's a frame from an SRB mounted camera (post-separation) showing the SSMEs running in the absence of SRB plumes. As stated by others, there's no real ...
- 189k
10
votes
ISP losses associated with exhaust vane TVC
Sutton edition 7 mentions them without too much detail
Jet vanes are pairs of heat-resistant, aerodynamic wing-shaped surfaces submerged in the exhaust jet of a fixed rocket nozzle. They were first ...
- 189k
10
votes
What is this South Korean rocket and why does it have separate yellow and blue exhaust plumes?
That's KSLV-2 aka Nuri. The first stage uses kerolox gas generator engines so the brighter flame is almost certainly ignited fuel-rich gas generator exhaust.
https://en.wikipedia.org/wiki/Nuri_(rocket)...
- 189k
10
votes
Accepted
Inconsistencies in calculating exhaust velocity
You are simply calculating the wrong parameter.
You are calculating exhaust velocity. You can't calculate this without knowledge of the nozzle geometry because exit plane pressure is used in the ...
- 189k
9
votes
Does the luminous blue shockwave from the RS-25 engine appear to be rectangular?
This should be considered a supplementary answer.
The Rectangular shape looks quite convincing, but remember we can only see the back part of the flame clearly.
There are other mechanisms by which ...
- 6,511
9
votes
Accepted
Does the luminous blue shockwave from the RS-25 engine appear to be rectangular?
The shock cone is not rectangular in any way when the engine is being tested, just as it is not in flight.
I finally ran across a different camera angle view of the same test stand (from slightly ...
- 189k
9
votes
Apollo 4 vs Apollo 8 plume
@russell-borogove explains that the plume changes during flight. We don't know the precise height when the two photographs were taken (both are labelled "climbing after lift-off" in the NASA archive).
...
- 15.2k
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
Is it possible to create different colors in rocket exhaust?
There are several ways to do this.
Fluorescence
Night time launch close to sunset or sunrise so that the rocket quickly reaches an altitude where it is illuminated by the Sun. The bright sunlight ...
- 151k
7
votes
Accepted
Does "What happens beyond Kármán, stays beyond Kármán"?
It’s meaningless to talk about orbital dynamics for gases. The mean free path up through and including cis-lunar space is much shorter than any useful orbital path. For example, figure 14-6 in ...
- 12.9k
7
votes
Do spacecraft ever release unneeded gases into space?
Section 30.4 of this NASA document describes passivation of spacecraft at end of life. The objective is to remove all sources of stored energy including pressurized gases and the way to do it is to ...
- 2,117
7
votes
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Is the unusual pattern/shape of SpaceX exhaust due to atmospheric pressure?
During the earlier parts of the flight, two things are different: the atmospheric pressure is higher, limiting the expansion of the exhaust, and the rocket is moving slower and ejecting its exhaust at ...
- 10.9k
7
votes
What color would the exhaust of an antimatter rocket be?
As noted in the comments - there may be nothing to see.
If your magic antimatter rocket is just slapping matter and anti matter together and defeating physics to get all the resulting products ...
- 25k
6
votes
Accepted
What flame is SpaceX's Hans Koenigsmann describing in his presentation?
The jumping flame was the gas generator exhaust.
You can see that as the bronze-ish coloured smaller cylinder on the side of the engine in this picture of Merlin 1D engines in the factory.
You can ...
- 80.5k
6
votes
Temperature and pressure of rocket exhaust
The temperature and pressure inside the engine's combustion chamber is very high -- in the ballpark of 3400º C and 100 atmospheres for the Falcon Heavy's Merlin engines.
However, the bell-shaped ...
- 172k
6
votes
Accepted
What is the 'Summerfield criterion' regarding rocket exhaust expansion
The Ralf Stark paper linked from the answer which mentions the Summerfield and Schmucker criteria ends with a list of references; among them are a 1973 Schmucker paper (translated in 1984, here) and a ...
- 172k
6
votes
Do spacecraft ever release unneeded gases into space?
There was a proposal by Mars One for a mission to Mars. It suggested using hydroponics to produce oxygen.
But a MIT study reviewed it and showed that this model could not work, because the plants ...
- 80.5k
6
votes
What is the velocity distribution of the exhaust for a typical rocket engine?
@RussellBorogove's answer mentions temperatures of roughly 3700 K and 1800 K in the combustion chamber and exhaust of a big rocket engine.
The canonical Wikipedia plot of velocity and temperature for ...
- 151k
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