Talk-Polywell.org

I wonder why I've never heard of it before now. The system uses 64 identical engines in parallel in 3 stages, 48, 12, 4 engines for stages 1, 2, and 3 in order to launch 2 tons into orbit. Each liquid fueled engine, complete with fuel tank (about 10 inch dia.) is very, very simple, but throttalable with one moving part, a fuel valve. 6,000 static rocket engine tests and 16 single stage qualification tests achieving up to 50,000 ft altitude were made to prove the concept as feasible. It was canceled due to politics, not for fear of an ICBM for every terrorist, but because it was a German company during the cold war, and Russia really didn't want the Germans to have big rockets.

http://en.wikipedia.org/wiki/OTRAG_(rocket)
http://en.wikipedia.org/wiki/OTRAG

Aero wrote:I wonder why I've never heard of it before now. The system uses 64 identical engines in parallel in 3 stages, 48, 12, 4 engines for stages 1, 2, and 3 in order to launch 2 tons into orbit. Each liquid fueled engine, complete with fuel tank (about 10 inch dia.) is very, very simple, but throttalable with one moving part, a fuel valve. 6,000 static rocket engine tests and 16 single stage qualification tests achieving up to 50,000 ft altitude were made to prove the concept as feasible. It was canceled due to politics, not for fear of an ICBM for every terrorist, but because it was a German company during the cold war, and Russia really didn't want the Germans to have big rockets.

http://en.wikipedia.org/wiki/OTRAG_(rocket)
http://en.wikipedia.org/wiki/OTRAG

I actually remember this being in the news back in the day, portrayed as a conspiracy by a german company to supply Libya with ballistic missiles, one of Reagan's pretexts for messing around with Khaddafi.

It has been said that rockets are basically turbopumps. That is, the vast cost of a rocket is just in the turbopumps. This is why rockets like Sea Dragon can get you in to space for dollars per kg.

Turbopumps will eventually be phased out if the private space sector is allowed to prosper as per Obama's new direction. It's just a matter of time.

Commercial aviation operates with massive turbopumps for air. They are called jet engines. They are used because they are the best power per dollar available. I don't really see how rockets are all that much different.

Space launch will become economical when we stop using disintegrating totem poles.

jet planes also don't spend thousands/millions per pump just to throw them away.

I get the impression that pressure feed isn't terribly feasible for larger systems. The guys with the rocket racing league tried piston pumps, and found they gave the flow rate needed at much lower cost.

Perhaps a gas generator? There are many systems that are run off of high pressure gas coming from fuel pellets. Basically, you'd have a small solid rocket motor at the top of the tank, and the pressurized gas coming out is used to pressurize the tank.

KitemanSA wrote:Space launch will become economical when we stop using disintegrating totem poles.

ROTFL this made my day!

Giorgio wrote:

KitemanSA wrote:Space launch will become economical when we stop using disintegrating totem poles.

ROTFL this made my day!

Assuming we are restricted to chemical boosters in the short to medium term, ELVs are the way to go. SSTO has been nothing but a delusional unicorn.

http://www.astronautix.com/articles/arosaway.htm

Of course, if EMC2 proves out Polywell in the next few years, that assumption collapses.

I wrote:Space launch will become economical when we stop using disintegrating totem poles.

kunkmiester wrote:jet planes also don't spend thousands/millions per pump just to throw them away.

Yup, pretty much what I said.

Giorgio wrote:

KitemanSA wrote:Space launch will become economical when we stop using disintegrating totem poles.

ROTFL this made my day!

Happy to be of service!

djolds1 wrote: Assuming we are restricted to chemical boosters in the short to medium term, ELVs are the way to go. SSTO has been nothing but a delusional unicorn.

GIGO. Ok maybe this should be "BABR" (bad assumption, bad result).

All launch related materials have terms related to what total velocity change they are effective over.

With rockets, it is exit velocity, or specific impulse. For most fuels, the efficient velocity change capability is on the order of two or three km/sec. Beyond this delta V, the fuel fraction starts growing exponetially. This is why you need about two or three stages for efficient launch.

Current generation cable (tether) material is about 2 km/sec.

So an endo-atmospheric tether to provide the first 2km/sec, a reusable (or very cheap disposable) rocket to provide the next 3, and an orbital tether to provide the final 2ish would make a very efficient, mostly or totally resuable launch system with current technology.

Armadillo aerospace is saying that their plan is to make many stage reusable rockets. The idea is to stack a whole bunch ot them and keep dropping the bottom ones when they run low on fuel. The dropped stages land themselves and are ready for refueling. I can imagine the first stage lifting the stack for 100 feet before releasing. A different approach for an RLV, to be sure. It might not be efficient, but if the only cost is fuel, it would be cost effective. They have worked with the guys from OTRAG and have some of their original equiptment (!). I am sure that I am explaining it poorly, but a possibly viable idea. I would worry about failure modes, but that is just me.

Flyback lower stages have been envisioned for a LOONNGG time, but it usually seems that the flyback provision put in a ROCKET destroys the payload capacity.

I've often wondered if a pulse/ram jet could be used for an effective flyback booster in lieu of the GEM-60s that Deltas use.

KitemanSA wrote:Flyback lower stages have been envisioned for a LOONNGG time, but it usually seems that the flyback provision put in a ROCKET destroys the payload capacity.

I've often wondered if a pulse/ram jet could be used for an effective flyback booster in lieu of the GEM-60s that Deltas use.

I would agree that it does make it very inefficient, but if all you pay for that is fuel, and that is cheap, does it matter? I do agree with you that there would be a point of diminishing returns and I don't see a heavy lifter in this, but for small payloads (say cargo or small sats), it looks interesting. I have also wondered about changing the design for stages that would only operate in the atmosphere. If you only want it to go for 1000 feet, why not make it airbreathing?