Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: I have a very basic delta v question


Member

Status: Offline
Posts: 14
Date:
I have a very basic delta v question


I am using this equasion for calculation delta V:

dV = ve * ln(m0 / m1)

dV is the Delta-V

ve is the exhaust velocity of the rocket engine(s). This is Isp in seconds * 9.81

m0 is the mass of your entire spacecraft before you ignite the eniges

m1 is the mass of your enitre spacecraft after the engine has been turned off.

I tried running it on the apollow lunar module assent stage with data from:

http://en.wikipedia.org/wiki/Apollo_Lunar_Module

It shows that the mass including fuel is 4,670 Kg
the empty mass is 4,670Kg - 2,353Kg = 2,317 Kg
and the speciffic impulse of the assent stage engine is 290 seconds

I ran the calculation on my spread sheet and got a delta V of 203.26 m/s far lower than the 1.6 Km/s needed for moon to lunar orbit according to this link:

http://en.wikipedia.org/wiki/Delta-v_budget

What am I doing wrong with my calculations?

Thanks in advance

__________________


Senior Member

Status: Offline
Posts: 366
Date:

I get dv=290 sec *9.8 m/sec^2*ln(4670 kg/2353 kg)=1948 m/sec



__________________


Member

Status: Offline
Posts: 14
Date:

Oh! I didn't multiply ISP by the acceleration of earths gravity. Doh!

Thats better

__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.

Tweet this page Post to Digg Post to Del.icio.us


Create your own FREE Forum
Report Abuse
Powered by ActiveBoard