Your links seem to lead to a short description of what they are going to do without any idea of how they got there. I didn’t get anything to form an opinion from them.

I’m not an aerospace engineer either. My education in this field is self inflicted and it shows. Lack of funds is my reason for throwing these ideas out there in the hope that some of it proves useful to somebody in the real..

The aerospike/heatshield you suggest seems to resemble Rotary Rockets’ concept from the late 1990s. Except that their engines rotated. The main problem as you noted is the expense and risk. Someday it will be different. I got one paragragh from your transpiration link. It seems that they are working the problem.

Using available thrust chambers and salvaged turbine assemblies And tested landing systems seems to be the way forward to me. The saddlespike could be tested in a weekend by glassing a couple of short bell nozzles together. A pump system could be designed around a salvaged aircraft turbine disk, turbine nozzle, shaft, and bearings. Armadillo could design a verticle landing system for an X38 type vehicle to eliminate the parachutes and uncontrolled landings, really important for injured crew. And so on.

What attracts me most is the rather shallow depth and small size of the combustion chambers. This means that one could think about having a VTVL vehicle with a large, round bottom, wrapped around a spherical tank, in which the combustion chambers are embedded that could double as the TPS for orbital return. A material that I’ve thought about is silcon carbide as a nanostructured ceramic forming polymer, such as Starfire Materials sells:
http://www.starfiresystems.com/
These materials are good up to 3300F and can be formed into a variety of shapes.

One could combine this with transpiration cooling for the thrust chamber. Transpiration cooling seems to result in some ISP improvement for pump fed engines. There’s a great paper from DLRF about transpiration cooled thrust chambers (C/C rather than SiC though):
http://elib.dlr.de/15168/
A properly engineered transpiration cooling system could provide some thermal mitigation on orbital return as well.

What’s the point of all this? Basically weight reduction through using lighter materials and through having one assembly perform two functions: thrust on up and TPS on the way back.

But who knows, maybe it won’t even work, like I said, I’m not an aerospace engineer. And, even if it did, like John pointed out in his blog post, none of the NewSpace startups can try something like this, it’s too risky. In a startup, you get to push the envelope in one direction (for example, with Armadillo, it’s throttable, steerable engines) but that’s it. Any more and you’re risking commercial viability.

http://www.spaceref.com/news/viewpr.html?pid=12631

It wasn’t a linear aerospike though.

The two designs shown are suposed to be a traditional linear aerospike and the new saddlespike. The saddlespike is the only new type engine shown.

If the right, left, and bottom sides of the box shown are open to the atmosphere, then yes. It is like two bell nozzles with doors cut in one wall to the outside, and connecting channel between the two for the aerospike area. The drawing was not supposed to imply wider bell than normal. It should thin at the sides rather than the middle and increase in thickness as altitude increases.

To me, it does not resemble an expander deflector at all. I do have a track record of not understanding the meaning of a question however. Sometimes I might agree if I fully understand your meaning.

The resultant hot gases are expanded through the nozzle 425 . Because the nozzle itself is manufactured of the solid fuel material (such as acrylic), the size of the nozzle expands as the motor burns. That is, at least a portion of the nozzle itself is burned and consumed because the nozzle is made of the solid fuel material. The initial flare of the nozzle 425 can be varied based on the altitude at which the motor is initially fired.
http://www.freepatentsonline.com/y2007/0261386.html

And Also:
The annular hybrid motor is an improvement to hybrid rocket motor technology that can be used for a wide range of applications. The technology will lead to improvements in hybrid payload mass fraction, increased performance during throttling, and reduced costs associated with casting hybrid fuel grains. The technology is highly scalable and can be used for applications ranging from small thrusters on satellites, to launch vehicle booster applications.
http://sbir.nasa.gov/SBIR/abstracts/07/sbir/phase1/SBIR-07-1-X9.04-8618.html?solicitationId=SBIR_07_P1

Thanks, looking forward to any comments.

I remember endwalls though much smaller than I drew. If you are right, then thrust/weight and cooling would be much easier. Redneck style, I think in terms of building large endwalls on a test article, and taking it to the test stand with a portable grinder. Cut the walls back between each test fire until you find the sweet spot.

You also corrected me on firing of the RS2200. I didn’t think it had ever been fired all up ever.

But having seen this beautiful picture of a XRS-2200 test firing again, I have to say that I seems they didn’t bother with sidewalls at all for the linear aerospike: http://en.wikipedia.org/wiki/Image:Twin_Linear_Aerospike_XRS-2200_Engine.jpg

Tim,
Right in one. By using vanes to control the recirculation area, it might be possible to control the vehicle without the moving surfaces actually contacting the fast moving expansion stream. If that can work, then split rudders become feasible.

Jon,
I’m not going to the mat for this specific approach, I’ve got notebooks of others. Sturgeons law applies to my ideas. I will consider it a good day if someone that builds hardware tells me how stupid my orriginal was and how they fixed it.