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.
http://en.wikipedia.org/wiki/Lockheed_Martin_X-33
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.
http://en.wikipedia.org/wiki/Linear_Aerospike_SR-71_Experiment
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.
https://theartsmechanical.wordpress.com/2016/05/27/scary-cold-war-stuff/
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.
https://theartsmechanical.wordpress.com/2016/03/12/what-does-it-taketo-build-a-resusable-launcher/
http://en.wikipedia.org/wiki/Single-stage-to-orbit
https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X
Jerry Pournelle on X projects and getting to space.
http://www.jerrypournelle.com/reports/jerryp/gettospace.html
Getting there in bits and pieces, testing along the way.
http://www.popularmechanics.com/space/rockets/a17574/masten-space-systems/
https://theconversation.com/its-not-rocket-science-we-need-a-better-way-to-get-to-space-45751
http://nextbigfuture.com/2016/04/darpa-xs-1-spaceplane-program-to-ease.html
The Arts Mechanical 
Remember, for the Obama administration, the American space program was a symbol of American imperialism and needed to be shut down. Yielding the high ground to peace-loving countries like Russia and China is in the best interest of the world.
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Bill, stop spouting ATK propaganda. The major disputes over the Administration’s Space Policy have to do with whether the COTS-D/Commercial Crew program, started under Bush after the Columbia disaster, will be allowed to continue so far that it undermines the political clout NASA Center budgets give Congressional committee Chairs in Texas and Alabama. That and the fact that ATK’s Shuttle boosters were specified by the Senators through their committee staffers, in the law passed in 2010, alongside the Shuttle Main Engines, all pre-1972 technology, whose contracts went to the old cost+ contractors in Texas and Alabama, is really what is being fought over in NASA’s current policy squabbles. There are no payloads funded by Congress that will require the Senate Launch System, as it is known inside the industry. The Senators want their pork, and Obama is resisting giving it to them.
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Or the Delta Clipper/DC-X. IT was doing vertical takeoffs and landings 20 years ago, long before SpaceX and Blue Origin. . .
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Yes, it was, but it was being funded by those horrible military types under that never-to-be-sufficiently excoriated Ballistic Missile Defense group, SDIO. Therefore, the first Clinton administration was not going to let that move forwards. By 1996 it was dead.
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On the “disintegrating totem poles”, and single stage to orbit: While it is true that not being able to reuse rockets costs a lot of money, there are reasons that we stage them. (Reasons that we have to use staging given certain structural mass fraction requirements, and the Isp of current engines).
To reach orbit, you need something like 9 km/sec of delta-V (depending a bit on trajectory: some of that is drag and gravity losses.) If you want to use the highest jet-speed rocket engines we have (LOX/LH2, and LH2 is it’s own pain in the ass to work with), you have something on the order of 400 sec Isp, then you need a propellant mass fraction for a single stage vehicle of 90%. For kerosene/LOX (320ish sec) it would need to be 95% propellant mass.
The people backing the Venture star project thought that that might be barely possible with light enough composite fuel tanks and an engine that wrung the last half second of specific impulse out of LH2/LOX. Unfortunately, hydrogen is not very dense, has to be kept at extremely cold temperatures, and that ended up cracking the eggshell-composite-tanks of the vehicle.
Agreed that they tried to do too many things with the testbed. I think the program started as a suborbital test-bed, but politics turned it into the *one-true-shuttle-replacement* that can do everything for everyone.
Rocket designers building orbital rockets are entirely correct to stage their vehicles. If you want to use engines that we have today, propellants like kerosene that are less of a pain to work with than LH2, and want some structural mass fraction for each stage so that the whole thing is more substantial than a wobbly tinfoil fuel balloon, then staging allows you to do that.
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I agree. You’re not going to get anywhere near an economical launch vehicle with an SSTO system. The technical problem is too difficult. I believe it can be done, but with great development cost. Since amortized development cost is a larger component of space launch cost than vehicle hardware, you would be solving your 2nd most difficult problem by making your biggest problem even harder! But if you notice, many of the early supposed SSTO designs (like Phillip Bono’s Rhombus, Pegasus, etc.) were not true SSTOs. They used cheap expendable drop tanks to reduce the difficulty of single stage to orbit down to something like one and a half stages to orbit… a small sacrifice in vehicle hardware cost to get a big savings in development cost. We are a long way from having the tech or flight rate to see an economical true SSTO. (BTW, at our engine thrust to weight levels SSTO+drop tanks is almost surely going to be more economical than SSTO+SRBs). See: http://www.jupiter-research.com/s/In-Defense-of-External-Tanks.ppt
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Just saying that it’s not an arbitrary aesthetic choice to use staging, nor is it “leftover” from ICBMs. We basically have to stage rockets if we want to reach orbit. I recall reading designs from the 70s and 80s for staged spaceplane vehicles: Truly gigantic first stage planes lifting second stage almost-orbiters, with a light expendable third stage kicker engine.
The thing about spaceplanes though is that wings may simplify launch and landing operations, but for the rest of the flight profile they add weight and drag: The advantages of using any airport for launch might outweigh any other inefficiencies, but even that isn’t cut and dry.
Basically, as long as we’re confined to using stored chemical energy for propulsion, space travel will always be a marginal thing that our materials barely allow us to accomplish.
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Interesting information about the Al-Li fuel tank though. If they were getting lighter tanks using that material, then it was indeed crazy to insist on composites.
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Reblogged this on KCJones.
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The nuclear rocket engine was my biggest disappointment. NERVA was ready for a test flight but the Nixon Administration axed it. The core technology lived on in the pebble bed power reactors but even that’s defunct.
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— 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. —
The weird veneration being bestowed on simulations has me baffled. A simulation is only as good as its ability to replicate the workings of Nature. Until the physical laws and interactions that would occur in actuality are completely understood, it’s solely a tool for speculation. (Cf. all the noise over “global warming.”) When it’s applied to a device that hasn’t yet been tested in real-world conditions, it’s not a method for observation and discovery, but a guess at what that device would do.
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I would have to agree with this analysis. As a mathematician pretending to be a software engineer wondering how I can get back into mathematics, I have a particular interest in finite element analysis, if only I could find the time to experiment with it! The thing about FEA is that it allows us to both simulate a physical process that’s generally well-understood (involving things like heat transfer and friction, for example) and tweak the design in a way we otherwise couldn’t (just imagine trying to build a new engine and run it for hundreds of hours just to see what the change in a valve size would do!), but it’s not a substitute for actually going out and building something — if, for no other reason, than the fact that we aren’t going to Mars on a computer simulation.
And in particular, I don’t trust climate models, because none of yet have demonstrated predictive value. They remind me too much of the stock market models that discover patterns, like a dip in the technology sector every Tuesday, except Tuesdays in a week with a Blue Moon, that, because of all the tweaks that have been made, are very good at predicting what happened decades into the past, but have absolutely no power predicting the future…
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Actually Pratt & Whitney just released their new geared turbofan engines. the development of which took 30 years, most of which was testing. Yes, you can simulate some things, but in the end you need real parts in real engines, which means that, for Pratt you have run an engine for 20k hours or more for a test. And you instrument the hell out of the test.
https://theartsmechanical.wordpress.com/2016/05/03/pratts-new-engine-the-pw1000g/
As for the climate models, computer models in general have proven to be poor oracles. Yet seemingly serious people continue to believe in them.
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Total re-usability of launch vehicle hardware is NOT the silver bullet for economical space launch. Not even if combined with aircraft-like operations either. That is because the largest cost for almost all space launch systems is not hardware or operations costs. The biggest cost is amortized development cost, and you can’t solve that problem by taking on a difficult development challenge like a fully reusable launch vehicle! See: http://www.jupiter-research.com/s/Propulsion-Economic-Considerations-for-Next-Generation-Space-Launch.pdf
That is why space launch vehicles almost always had weapon system ancestors… sharing development cost through product evolution and component reuse is an proven solution to the development cost problem. (Also using a small, talented development team working in an isolated location where there isn’t much else to do and so unneeded managers aren’t likely to want to come by and micromanage something or get ideas on how the project objectives can be changed halfway through the design). A less successful but common solution is to just lie about what the flight-rate will be and claim there will be hundreds of flights to amortize the development cost over.
Space-X’s approach to starting with the disintegrating totem-pole and evolving reusability from the lower stages up seems like a sound approach to developing an economical cargo launch vehicle once you actually look at the cost of things.
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“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.”
No.
They did not forget that.
The NASA proposal evaluation group were *told*to*ignore* that in early 1996!
Of the three proposals for X-33, Rockwell’s was so conservative it would not have led to the desired tech. Lockheed/Martin’s was so complex, with 39 different new technologies in the critical path to success, that It would have required a major miracle for all of them to work. While people complain about the lobed tanks, the software was in far worse shape, as just one instance. However, the McDonnel-Douglas/Boeing proposal was based in what had been learned on DC-X, and was quite capable of proving the tech needed. However, McDonnel-Douglas was considered by the Clinton administration to be tainted, by association with the DC-X work for SDIO and the military, and to be “a Republican outfit”. By contrast, Lockheed/Martin was, by February of 1996, the largest single corporate donor to the Clinton/Gore re-election campaign fund.
When this NASA evaluation was complete, they sent it to Office of Science and Technology Policy, as was done for all major decisions. OSTP sent down a young staffer to ask questions. She asked, for instance, about how the Thermal Management System could be known to work. She was told that it had been proven in McDonnel work under the SABRE program for maneuvering re-entry warheads in the 1960s. She was appalled that military programs were going to influence NASA decisions. The NASA group carefully refrained from asking what influenced the design of the jet engine tech that let her fly into D.C. from Stanford.
Her reply, when told, “In the end, Delta Clipper meets the criteria best”, was simple “Then change your criteria!” They knew what they had been told to do, and did it. Calling it a NASA decision, however, would be, …only pro-forma.
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