Re: Confronting The Singularity Conference

From: Spike Jones (
Date: Fri May 26 2000 - 23:34:00 MDT

Michael S. Lorrey wrote:

> This is something I've wondered. If liquid fuel is so much better, why
> does the shuttle, the Delta, the Araine, the Titan, etc all need solid
> boosters to get decent enough mass fractions to put decent payloads in
> orbit?

Solid fuel rockets are a good deal for launch from the deck. Altho
they have lower specific thrust (thrust per unit mass) than liquids,
they have very good thrust per unit volume, which is important
if you need to push something thru the atmosphere. Sure solids
and their pressure vessels are heavy, but consider that they dont
need to go all that high, and they are good for recovering and
refurbishing. Doug Jones may have a comment to make regarding
this, but in general solid rocket strap-ons are a good deal for
launch vehicles.

> I was wondering if people were biased toward hydrogen merely for
> purists sake. Sure you get great Isp, but you get great Isp from an ion
> engine too, and you wouldn't want to power a launch system with an ion
> engine.

Nah. While ion engines have enormous specific thrust, they have very
low total thrust. Makes for good orbit transfer vehicles, since you have
plenty of time, but no good for launchers, even with any imaginable
breakthrus. What say ye, Doug? spike

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