Re: SPACE: Launch from ULDB?

From: Spike Jones (
Date: Wed Mar 14 2001 - 23:33:56 MST

Michael Lorrey wrote:

> (btw: what is the
> equation to use to calculate mass fractions?

mass fraction ~ exp(9100/Ve)

You need a delta vee of around 9100 meters per second to
acheive orbit, if memory serves. Doug, is this about right?
This estimates the loss from atmospheric drag and gravity
losses. I can sharpen this up if you want to get more exact.

Then the mass fraction is exp(-9100/exhaust velocity).
The exhaust velocity is about 3600 on the deck and
goes up to about 4500 in vacuum, if you are using
lox and H2. Kerosene and lox is about 3000 m/sec
at 1 Atm. Problem is my reference material is all
at work at Im at home going on memory, and my
calcs on this stuff are all several years old.

> Spike, can you post up your spreadsheet?

Thats a good question. Can we post spreadsheets
onlist? spike

This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:59:40 MDT