Does anyone have promotional material from ATK’s EELV bid circa 1996? If I remember correctly, they proposed clustering up to three shuttle SRBs. I wonder if they published performance data for those concepts.

One of the justifications for Ares I is that it reduces the development cost of Ares V. Presumably one of the contributions is the 5 segment SRB. Taking a page from John’s concept, I wonder if the Ares V development could be made cheaper by using four unmodified 4 segment SRBs. We might call this new vehicle Ares VI. I would think the additional thrust would allow the liquid core to be smaller and more manageable to develop, perhaps even small enough to be derived from the shuttle ET. I recall seeing concepts along these lines in the 1980′s so it is hardly an original thought.

It’s almost impossible to air-start a SSME. It’s a 120 Ton payload to make it start.

Here is a chart of the SRB thrust over time normalized to sea level pressure: http://en.wikipedia.org/wiki/File:Srbthrust2.jpg

The big valley in the graph is likely all because of Max-Q.

I believe your point is that the current SRBs are very specifically tailered the the Shuttle stack as it currently exists and to bolt them to any other stack would leave them mismatched to the application.

My point is that the thrust of the current SRBs are well known throughout the flight profile and that the new upper stage would need to be tailered to that instead of starting over as in der Griffenschaft. With the exact thrust and mass of the SRB known at any given second, it would seem that the upper stage could be designed to match that thrust profile. I believe that some mismatch could be tolerated. It’s not like the astronauts are going to unexpectedly experience 8 G.

I believe that to redesign the solid to the extent currently being done is more difficult than designing a whole new liquid booster. I believe that license building RD170s and designing a new first stage around two of them would be much cheaper and far more capable than this kludge.

Sometimes we talk past each other, but we seem to converge after a while.

So I like the idea of reusing the solids – exactly as they are. Instead of telling the engineering team “we want to lift X, design us a rocket system,” they should say “we want to lift X, using our existing SRBs and engines – design a rocket system around them.”

The designed rocket would have “terrible” performance. For example, to address the SRB thrust curves being wrong a huge tank of water would be added to the design. As the rocket goes up, the water is thrown overboard at the rate required to keep the thrust at the correct point. That means your rocket would be easily twice as heavy as required for the job… but that doesn’t matter! The fact is, mass costs nothing. Propellant costs nothing. New major systems are impossible to get at any price! We just do not have the capability / political will. Billions will be spent, programs will appear and disappear, but nothing will be created.

If you want to lift X, design your rocket to lift 2X. It is easy to throw away unneeded performance after the design is done.