"Rüdiger Klaehn" wrote in message
oups.com...
I found it:

http://www.flightglobal.com/Articles...n/200/203670/I
nflatable+launcher+more+than+hot+air.html

It is a little low on details, but it looks like it uses an
annular aerospike nozzle.

It also has a very low payload fraction. Fueled weight
is 47t, payload into an unspecified low earth orbit is
just 150kg.

I wonder why they have separate propellant tanks
instead of integrating them with the aeroshell.

Me too. This is a very interesting but strange design.

It says that such a vehicle if used for Mars sample return, would be one
third the weight of a conventional vehicle. I am not sure that it uses
an annular aerospike, it would seem silly to embrace such added
complexity at this stage, though the position of the helium tank does
suggest it.

Strange things:

- It uses spherical tanks, inflatable tanks like composite tanks do not
need to be spherical.

- It looks pressure fed, requiring heavy tanks. While inflatable tanks
still have an advantage at high pressure they have a far greater
advantage as low pressure balloon tanks. Inflatable tanks do not suffer
the same minimum gauge constraints and buckling during ground handling
is not a problem.

- There seems to have been no effort to make the tanks structurally self
supporting, they are supported by a separate carbon fiber frame which
seems totally unnecessary and negates many of the advantages of using
such tanks.

Having said all that it still looks very interesting indeed and to have
a much lower drymass than conventional vehicles. A definite positive
step in the right direction.

Having the propellant tanks inside the inflatable aeroshell does allow
one to collapse the tanks so as to use the last drops of propellant. It
also helps prevent icing on the LOX tank as the air inside the aeroshell
becomes dehumidified. Nor does this necessarily require much more mass
as the aeroshell pressure adds to the tank pressure. One serious concern
I have with such a configuration is that a small propellant leak could
lead to a very nasty explosion inside the aeroshell. They obviously
think this is not prohibitive, though I think I would still favour an
external tank approach, primarily for this reason. I also like the idea
of having both the propellant tanks sitting on the engine, saves on
plumbing and tank structural support.

Another trick that seems possible using said inflatable materials is the
construction of a very light weight positive displacement turbo pump
equivalent. Kind of like a cross between a Flowmetrics pressure pump and
a turbopump, it should have most of the advantages of both. This might
be ideally suited to such small low cost launch vehicles.

Pete.