All Questions
8
questions
8
votes
3
answers
14k
views
What does the exhaust plume of a rocket look like in vacuum?
There are plenty of photos of rocket tests and launches in atmosphere, and in these the exhaust plume tends to be a long thin flame.
Is this true for when rocket engines operate in a vacuum? My guess ...
- 83
9
votes
3
answers
4k
views
Oberth effect for Earth vehicles
I don't understand this and must ask a probably very stoopid question here:
The Oberth effect says that a rocket is much more efficient when (and in the orbital direction of) a payload when it ...
- 27k
20
votes
4
answers
8k
views
What is the "pendulum rocket fallacy" as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?
I've received comments that explain to me that the analogy between rocket attitude control during a hovering maneuver and the act of balancing pencil on the end of a finger is a helpful and good one; ...
- 149k
4
votes
2
answers
457
views
Could a fat rocket be used on Mars?
Since Mars' atmosphere is around 2% the density of Earth's then could a much wider rocket achieve orbit?
Could the rocket be in the shape of a capsule or an optimal shape for reentry on Earth?
- 1
2
votes
1
answer
2k
views
How did NASA calculate 22 million "rocket horsepower" for the SLS Booster?
This answer to Does NASA really report the power of rockets in horsepower? cites NASA news item Space Launch System Booster Aimed and Ready to Fire which says
"What's impressive about this test is ...
- 149k
13
votes
6
answers
3k
views
Why does this formula say rocket efficiency depends on velocity?
Wikipedia gives the following equation for the efficiency $\eta_p$ of an engine here:
$$\eta_p= \frac {2\, (\frac {v} {v_e})} {1 + ( \frac {v} {v_e} )^2 }$$
where $v$ is the rocket speed and $v_e$ ...
- 2,035
6
votes
2
answers
793
views
Modeling a rocket using Tsiolkovsky's equation and ordinary differential equations
So I have this uni assignment to make a model out of ODEs, and my idea was to use rockets. After some research I found about Tsiolkovsky's equation and tried using it on a Falcon 9 (disconsidering ...
- 61
3
votes
5
answers
991
views
Why is hydrogen better than helium as remass?
I just watched a very good YouTube video on why nuclear engines might be useful, and it also goes into why Hall Effect thrusters are super good at squeezing obscene ISP out of things.
During the video,...
