All Questions
24
questions
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 $v_e$ ...
- 131
1
vote
0
answers
113
views
How high will this rocket be, when MECO occurs?
Find the altitude of the rocket at the time of engine cut-off.
Rocket Mass = 369208 kg,
Rocket Area = 391 m2,
Fuel = 170697 L,
Fuel density = 21 kg/l,
Exhaust Speed = 1338 m/s,
Exhaust Area = 164 m2
- 5,884
3
votes
1
answer
154
views
What is missing in the conversion of specific impulse from units of seconds to thrust/mass flow rate? [duplicate]
I was trying to get the Specific Impulse of the Saturn V engines, hoping for a value in N/kg/s, as I need to know the mass consumption rate per thrust value. Any and all sources give me the value in ...
- 170k
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 ...
8
votes
2
answers
878
views
Is engine thrust noticeably increased near the ground?
I know next to nothing about rocketry and space flight.
I assume that the majority of the force generated by a rocket's engine is simply the result of throwing gasses out of the bottom very fast, and ...
- 161
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,...
- 13.1k
1
vote
0
answers
71
views
What is the best place on the internet to learn basic physics needed for rocket engineering? [closed]
Does anyone know a site where everything is in one place and it teaches equations and pricipals from the basics?
- 184k
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
4
votes
3
answers
3k
views
What (if anything) limits the efficiency of a rocket engine?
Humans have developed lots of rockets. I observe that in most cases to increase the payload capacity we just increase the amount of fuel.
Is it not possible to exponentially increase the efficiency ...
- 1
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 ...
- 5,505
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; ...
CommunityBot
- 1
3
votes
1
answer
481
views
Pendulum rocket fallacy - so why *do* skyrockets have sticks?
This question is inspired by two, linked questions.
Skyrockets (of the pyrotechnic/firework kind) have guide sticks, which are (according to internet sources) to enhance stability: "The guide ...
- 1,088
4
votes
2
answers
758
views
Design of starship fins
How much can the falling speed of starship approximately be reduced by the bellyflop fall with fins? Are we talking about numbers around 5% or 50% here?
Wouldn't it make sense to put holes where the ...
5
votes
1
answer
802
views
Contracting rocket engine nozzles
The efficiency of rocket engine nozzles depends greatly on their expansion ratio an how well the ambient pressure matches the rocket nozzles exit pressure. An optimal expansion ratio means that there ...
- 4,157
1
vote
0
answers
439
views
Can Chemical Engineer work on something related to space?
I am an undergraduate student (scientific section) living in Qatar. I have a big interest in astronomy and astrophysics and have participated in the IOAA (International Olympiad on Astronomy and ...
- 1,775