# Double stage Rocket Equation help!

1. Nov 23, 2009

### aeroenga

1. The problem statement, all variables and given/known data

okay the problem is there is a two stage rocket with a payload of 200kg and isp 2943m/s. It has a total delta v of 10km/s and at each stage it produces half of the total delta v.

The question is to calculate the initial mass prior to launch, ive been told also that for each stage x, msx which is the structural mass is related to the initial mass mox. (ratio provided as mox/msx = 10)

Also the final mass is defined as the mass of the structure of the second burner (ms2) + payload.

2. Relevant equations

delta v= cln(m0x/mex) equation (1)

mox/msx = 10 equation (2)

3. The attempt at a solution

started off with final mass me2 = ms2+ 200kg

then i know that from equation two i can write ms2x in terms of mo2x

me2 = 0.1mo2 + 200

then substitute this into equation (1) to find mo2x when making sure delta v = 5000m/s

which i find to be 2414.21kg

now the next stage is that i know mo1 is equal to the mass im trying to find out and it includes the payload too.

im really confused at what to do from this point onwards, do i just use equation (1) and say that:

m02 is equal to me1 and calculate mo1 from mo1/m02, for delta v = 5000m/s thus finding the total mass prior to launch?