On Jun 29, 6:55 pm, 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.

Sylvia.

I have probably looked at as many launch vehicle concepts
--rocket powered and airbreathers--as anybody in the world.
The devil is in the details. I would not consider Skylon
anywhere close to realistic. As for purely rocket-powered
approaches, I have never been able to convince myself
that any SSTO having a gross mass of
less than about 800 tonnes was very realistic. And for
HTOL, some type of ground cart to support the vehicle
at gross mass is probably necessary--thus making it
really an assisted SSTO, rather than a pure SSTO.

Staging--even subsonically at altitude or at low supersonic
speeds greatly relieves the challenge. IMO, staging
can sometimes be beneficial from the operations point
of view--as wsll as the performance point of view. SSTOs
are undoubtedly appealing from the psychological point
of view. However, they may not be a good way to run
an airline.

At some combination of size and yet-to-be-discovered
technology, SSTOs will make technical, economic and
marketing sense; but I don't see this happening soon.

Len