On 29 Jun, 23:55, Sylvia Else wrote:
David Cornell wrote:
If someone were to build an SSTO using realistic assumptions about mass
ratios and available power systems, how big a vehicle would be needed to
send (say) three people and a modest amount of cargo into LEO? I have
seen Apollo capsules in museums, so I am using them as my baseline.
Would such a thing be the size of a regular jetliner? Or the new Airbus
super jumbo jet? Or are we talking about a Zeppelin on steroids?

Also, how would these things scale? If we wanted to increase the crew
from three to four, would the vehicle size go up by a third? Or more?

Thanks

David Cornell

You didn't say so, but I'm assuming you mean a reusable craft.
Disposable SSTO's seem a waste of effort.

The most developed design I've seen for a reusable SSTO is

http://www.reactionengines.co.uk/skylon_vehicle.html

It has a payload of 12 tonnes, and a maximum takeoff weight around 280
tonnes, similar to that of a 777-300. It uses a new engine design with
some technological challenges, but they seem to have made some progress
with it. They're obviously financially constrained, so if you have a
spare $billion, I'm sure they be interested in talking.

Skylon is an automated system, and as such is not designed to have a
crew, but could carry people as payload. This document

http://www.reactionengines.co.uk/dow...56_118-126.pdf

discusses that application using a module carrying 40 people, though
that's obviously in a transport application (to a space hotel, perhaps).
If you have space tourism in mind, with passengers not leaving the craft
and floating around the cabin, then presumably they'd need more space
per passenger.

It's hard to say how this scales for a smaller payload, but at a guess,
I'd say you could get a craft to carry four people that was the size of
a small airliner in the 50 seat range.

There is one significant engineering fact that nobody seems to be
clear about and that is scaling. Suppose you double the size of
something. The weight and hence the stresses go up 8 fold whilst the
structural strength (cross sectional area) only goes up 4 times. Same
thing is true of reentry heat 8 times the heat, only 4 times the
airframe area.

I would like to see a hpersonic profile (missing in the paper) showing
exactly what the stresses are, both structural and thermal.

Some time ago I think it was Alex Terrell who initiated a discussion
on the Moon base. We got down to the question of competitions. Someone
suggested maintaining a car with a 2.5 sec time lag built in to
simulate a signal going back and forth from the Moon to Earth. Good
idea! I suggest extending this principle.

NASA has got some marvellous aerodynamic simulation software. What I
suggest is that we build, usig a CAD system a hypersonic plane, or
indeed any other SSTO configuration. Let us see what the problems with
it are. Does it fall apart before it gets to LEO? OK simulation is not
perfect but we will at least sort out the utterly hopeless.

I think that NASA should negotiate with its software providers on
license issues and organize a competition, no design barred until it
is proved not to work.

Quite clearly in the absence of aerdynamic and structural data we are
no furter forward. There may be but I have not seen it. What is a
hypersonic aircraft made out of? How hot does it get? There may be
answers somewhere - not in the reference.


- Ian Parker