Pete.

Sounds like a job for Aerojet’s TAN (Thrust Augmented Nozzle). See the Selenian post at http://selenianboondocks.com/2007/11/random-thought-thrust-augmented-aj26-60/

and also:

http://selenianboondocks.com/2007/11/thrust-augmented-nozzles/

One option to make either the Merlin or NK-33 more efficent for possible SSTO use would be carbon-carbon nozzle inserts inside upper-stage configured nozzles for the engines. These inserts would configure the nozzles for boost-phase effciency, then be ejected so the nozzles would be reconfigured for the rest of the flight. Still a long shot though. Until carbon nanotube derived materials are available for major fuselage cmponents, I don’t see how conventional engines could power an SSTO RLV, even with using a drop-tank to lose structural weight.

You could possibly build a “mixed mode” VTOL using Merlins plus RL-10s. Just guessing, I’d figure such a vehicle would have a GLOW in the 400K lb. range to match the derated thrust of 6 Merlins, with perhaps 3 RL-10s for the “second stage”. The cost of the RL-10s would kill the project, however, since they are in the double-digit million range, now. The project would end up at a few hundred millions to be a useful demonstrator.

FYI, Gwynne told me a few years ago that the “sale” price (if they were ever to sell, which is questionable to me) would be $5M per Merlin. So right there, the engines would cost you about $50-60M for one shipset.

You’re better off spending a little more on NK-33’s or even taking a one year development detour, calling the flometrics guys, and atleast seeing if you can make their system work. I think their system is going to be heavier than they say it will, but you can’t argue with their price.

If one could buy SpaceX Merlin engines for $1 Million each, how much would it cost to build an SSTO out of composites, and how long would it take, if re-usability was not a goal? Would this SSTO look something like the Roton ATV, and would you have Scaled Composites build your shell? The payload requirement would be 1,000 lbs to a 200 km reference orbit.

The big difference is that the first of those three has the least tolerance of failure, and the least payload density.

Perhaps a workable development program (to the extent it exists) would be to build and test the bejesus out of a propellant delivery vehicle that has the same geometry and payload capacity as a people mover. It would be suboptimal as a propellant-only carrier, but would wring out a lot of risk.

Assuming more than one stage (and referring to Jon’s earlier post on stage recovery), the first stage could be suboptimal for the orbital mission mass, but be better tailored to the recover / relaunch role.

One of the things that attract me to suborbital field is that a lot of the constraints that have driven launcher design (e.g. maximize mass ratios) are relaxed… and sometimes considerably.

And to echo other comments: excellent post, Jon.

If you have short-duration boosters to help get the vehicle off the pad in what is otherwise a viable near-SSTO RLV, that is another option. I’m talking about using small strap-on boosters as a “virtual catapult.”

We’ve all heard of, and even discussed, things like rocket sled or carrier-type catapult launch systems to start a launch sequence. The thing about such systems is they limit launches to wherever such a system has been built. Using short-duration, high-acceleration boosters would mean 1) the “catapult effect” becomes portable, and 2) that the boosters would travel a relatively short distance before separation, thus facilitating recovery and simplifying operational issues. For instance, a 20-second burn at 4 Gs might mean staging at about 5 miles and at about Mach 2. Very rough guess (perhaps optimistic on the Mach numbers, but, you get the concept), but recovering from 5 miles up, and perhaps 10-15 miles downrange is less complicated than a large, fly-back booster. One of you folks did an entry on a runway rocket sled that is another option. With land-based speed records now exceeding Mach 1, that may have merit. The “booster” never leaver the ground, but doesn’t need rails, just a runway. HOTOL flirted with that idea years ago.

Technologicasl game-changers: I imagine that we’ll see the first aircraft fuselages built primarily with carbon nanotube meterials within a decade. This could make a dramatic diffrence in RLV design, and possibly allow for SSTOs with conventional propulsion.

More potent, denser hydrocarbon propellants, like a mixture of Quadricyclane and JP-10, instead of RP-1. Combined with advanced composite vehicle bodies, it could alter the equation for RLVs dramatically.

I haven’t said anything about air-launch, as that is indeed a whole ‘nother discussion handled at length on your blog in the past.