[ExI] rocke fuel was Re: SpaceX launch

Eugen Leitl eugen at leitl.org
Fri Dec 10 21:47:42 UTC 2010

On Fri, Dec 10, 2010 at 10:07:17AM -0800, Adrian Tymes wrote:

> The first article gives a specific impulse of 850 seconds for a simple
> solid-core design.  The latter gives specific impulses of 250-450 for
> modern chemical (solid or liquid fuel) rockets.  Yes, there are better
> examples listed, but none that give 1G+ thrust.  (Fuel efficiency is

In terms of economy you're likely to employ a hybrid design.
A maglev launch stage (e.g. up Mount Chimborazo) instead of a first
chemical stage, second stage air-breathing scramjet/rocket hybrid
or simple chemical rocket, or laser driven ablation (not sure this
will ever work, though current prototypes are sure nifty).

Also, there's nothing fundamentally wrong with chemical rockets,
as long as your transport rate is limited, e.g. for a lunar bootstrap
using in-situ resources. Suited monkeys are quite pointless, so you'll
proceed to teleoperated robots shortly, and whether you teleoperate
them from a pressurized can nearby or from rotating ground centers (with
the advantage of 24/7 operation) only adds about 2 seconds of latency.
Which is an nuisance, but adaptable to in principle, and asks for
local reflex augmentation, and is a precursor for fully autonomous
designs where relativistic latency makes motoric loop coordination

> very desirable, but high thrust is required, for launching.  So we can
> ignore any engines that do not give 1G+ thrust for that purpose, no
> matter their other benefits, even though they may be superior after
> orbit is achieved.)

You will not get NERVA-type rockets approved, nevermind something
as dirty as an Orion. That's not a handicap, that's a feature.

Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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