andrewpreece wrote:

"Ian Stirling" wrote in message
snip
I'm budgeting for a very, very large contingancy delta-v, around a
kilometer a second, just in case.
Part of the design is to be able to cope with unexpected stage
underperformance, or the flame going out.

Fuel is cheap.

Fascinating: I thought at first you were making it up! AFAIK noone has done
anything like this, the X-prize contestants aren't anywhere near orbital
velocity and the performance needed in terms of fuel goes up as the square
of the velocity, and you reckon you've a km/sec delta-v as contingency! I am
all admiration Sir! I've seen other rocket groups' websites ( one group is
called MARS ) but none are quite as ambitious. The amount of human effort
needed to achieve the kind of performance you specify is considerable. Any
chance of a technical overview or is it all under wraps?

At the moment I'm working on ancillery systems, guidance and stuff, and
working out best ways of making cheap small regeneratively cooled rocket
engines.

In a way, it's not very ambitious.
Some groups are going for things like single stage or 2 stage to orbit.

This means that you almost have to go to extreme lengths to reduce the
weight of the vehicle, and are very highly penalised by small size due to
having to push through the atmosphere.
(adding a percent to the dry mass of a 1 or 2 stage vehicle can often be the
difference between having a payload, and not being able to reach orbit empty.

If you're willing to go with more stages, then in some ways things get
easier.
You throw away empty tanks along the way, which means that you don't have
to have one big very light tank.

You reduce the total mass you have to take to orbit, as the size of rocket
engine on the upper stages is smaller, hence lighter, so you don't have to
worry so much about the takeoff engines weight, or make it so that it can be
throttled down so far, and in some cases can eliminate the need for the
engine to be restartable.

All of this is good, as it makes the hard bits (rocket engine, ...) a little
easier, and means that instead of needing Aluminium-Lithium tanks, you can
go with not very good steel or fiberglass, can use screwfix 2.99 full-bore
ball valves instead of machining something exotic and light, ...

Yes, it may use 25 times more fuel than a 'good' rocket, but fuel is cheap.

(I'm aiming for a cost for the whole thing of only 10K )

This is for around a kilo to LEO.
For much more, this approach starts to break down, and you need to go to
appropriate high technology in some parts in order to keep costs down.
It doesn't make sense to (for example) make a much larger rocket out of
simple to construct steel, if the overall cost is lower with better
harder to weld steel.