Aerospike rocket engines:
The aerospike engine was to be used first on the x33 Venture Star, an attempt to gather information leading to a true reusable Single Stage To Orbit(SSTO) vehicle. Unfortunately the X33 died because of mission creep and cost overruns. Essentially the mission planner forgot what the X projects were for and tried for a fully flight ready vehicle when what was needed was an engine test bed. They truly forgot the KISS principle in design and development.
The fuel tank work needed to be done. Better composite structures are a must for aerospace progress. That work though, should have been done as more general project involving composite construction. After all, use of composites has been increasing across the aerospace industry and other industries as well.
Apparently the engines themselves performed more or less to spec, but without a vehicle test bed, there was nowhere to go with them. To say that you are gathering data for computer models doesn’t help. There’s only so much that you can learn if you don’t have an entire platform working together and the computer, is at best, an approximation. When it comes to composite structures on the razor’s edge where weight is concerned, more than likely an approximation that is nowhere near good enough.
The problem is that without an active X plane program developing those new platforms, we’re stuck still using base technologies from the 1950’s. The disintegrating totem pole, based on ballistic missiles has served the space industry for a long time now. For the most part every space launcher out there has one ballistic ICBM or another in it’s pedigree. The early liquid fueled ICBMs of the US and USSR provided the designs for engines and tankage that’s used in all the launch vehicles currently out there, indirectly in some cases, directly in others.
The problem is that ICBM’s weren’t designed as spaceships, they were designed as self propelled artillery. They were designed to be expended after firing, which works when you are planning to rain nuclear weapons on people but for keeping launch costs down, not so much. The only reason that the disintegrating totem poles were used for space access at all were because the Air Force and other military branches had already developed the technologies and the two sides of the Cold War were in a hurry to get to space.
The big problem is that without an alternative to disintegrating Totem poles access to space will always be rare and expensive. In the space world everything right now seems to be either static or going in reverse, relying on Russian vehicles that date back to the early days of rockets. Now the Proton/Soyuz/Progress platform has proven itself to be a more than reliable vehicle and there is a lot to be said with sticking with what works. The issue is that without a new vehicle we are stuck doing the same things over and over. It’s also hideously expensive to use, what with cost of maintaining Baikonur and fabricating launch vehicles for every launch.
If investment in space is going to move forward, a reusable launch vehicle is imperative. That doesn’t mean the slightly modified Falcon 9. It means a vehicle where the whole system gets recovered There have been numerous plans for reusable Single Stage To Orbit vehicles in the past, but nothing much has gotten past the paper stage. The DC/X being the exception, but NASA managed to prang the vehicle once they got their hands on it and nothing much has happened since.
That’s one reason why the X33 cancellation was a disappointment to me, at least. I was not in a position to understand what was going on viv a vis the computer modeling and all that stuff about the fuel tanks. As far as I’m concerned, letting that run the project away was just stupid, but I’m not a NASA program administrator. Still the need for a recoverable stage or single stage to orbit reusable launch vehicle hasn’t gone away. Here’s a stack of links on SSTO’s and other launch vehicle options.
Jerry Pournelle on X projects and getting to space.
Getting there in bits and pieces, testing along the way.