Rocket Propulsion: Calculating Specific Impulse for Return Mission

Click For Summary

Homework Help Overview

The discussion revolves around calculating the specific impulse of a rocket launched from Mars for a return mission to Earth. Participants are exploring the implications of using different gravitational constants in their calculations.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster questions whether to use Mars or Earth gravity in their calculations for specific impulse. Some participants challenge this by asking why Earth gravity would be relevant if the launch is from Mars. Others reference standard formulas for specific impulse and express uncertainty about their applicability in this context.

Discussion Status

Participants are actively engaging with the question of which gravitational constant to use, with some providing insights into the historical context of rocket launches. There is an ongoing exploration of the assumptions underlying the use of Earth-based formulas in a Martian context.

Contextual Notes

There is a mention of standard formulas for specific impulse being based on Earth conditions, which raises questions about their relevance to Mars. The discussion also highlights the need for clarity in the original question to avoid confusion.

praveenpandiyan
Messages
28
Reaction score
1
  1. well. I have this question. That my rocket is launched from mar in an return mission to earth. To calculate specific impulse of the rocket. Should i consider mar or Earth gravity and if why!? Help me with this
 
Physics news on Phys.org
If your rocket is being launched from Mars, why would you use Earth's gravity in your calculations?
 
problem Is we have formula for specific impulse for Earth standard..That Isp=Cj/Go
Cj-effective jet velocity
Go-gravity
..and that's the reason i asked..why its not Mars gravity! I am not sure of it.
 
praveenpandiyan said:
problem Is we have formula for specific impulse for Earth standard..That Isp=Cj/Go
Cj-effective jet velocity
Go-gravity
..and that's the reason i asked..why its not Mars gravity! I am not sure of it.

That's because until now, all rockets have been launched from earth, in Earth's gravity. If ever a probe lands on Mars and returns to Earth from there, obviously, Mars gravity will determine how much impulse will be required for the rocket to return to earth. It's like when Apollo went to the moon: did the lunar module need to exceed the gravitational pull of the moon or the earth?

If you had used the HW template per the rules of this forum, and provided the entire question as worded originally, perhaps this confusion of yours could have been resolved by now.
 

Similar threads

Liquid rocket engine excercise
  • · Replies 1 ·
Replies
1
Views
1K
Rocket + Connected Body Dynamics problem
  • · Replies 47 ·
2
Replies
47
Views
3K
How to calculate velocity of infinite-stage rocket?
  • · Replies 2 ·
Replies
2
Views
1K
When does nuclear thermal propulsion outperform chemical propulsion?
  • · Replies 10 ·
Replies
10
Views
3K
From circular orbit to elliptical orbit
  • · Replies 3 ·
Replies
3
Views
3K
Time dilation and length contraction for a rocket
  • · Replies 12 ·
Replies
12
Views
3K
How Do Impulse and Work Relate in Rocket Dynamics Homework Problems?
  • · Replies 2 ·
Replies
2
Views
1K
Pytels Dynamics 12.39: A rocket is launched vertically
  • · Replies 3 ·
Replies
3
Views
3K
Could a nuclear powered rocket be safely launched from Earth?
  • · Replies 21 ·
Replies
21
Views
3K
NASA NASA - Bimodal NTP/NEP with a Wave Rotor Topping Cycle
  • · Replies 1 ·
Replies
1
Views
4K