I think this may challenge claims that the X-33's composite hydrogen tank issues were unsurmountable.
Quote from: Patchouli on 06/24/2015 12:09 amI think this may challenge claims that the X-33's composite hydrogen tank issues were unsurmountable.That's a very simple shape compared to what the X-33's were; although I agree they could have fixed it. In the end the aluminum tanks would have been lighter.
This is where I was thinking a mashup of the Rockwell and MD proposals might have born more fruit. At least not needed so much new hardware. Then traditional cylindrical tanks could have been used, and so composites could have been easier. And the shape could have been easier (if a tail-landing cylindrical shape like the MD vs. the airplane shape of the Rockwell). RS-25's could perhaps have been used, instead of the new aerospike. It looks like both the MD and Rockwell used it...or something that looks a lot like it.
There was a push to make a leap using all new tech so McD won. The other two were more incremental and less a leap foward.
Quote from: Lobo on 06/29/2015 06:09 pmThis is where I was thinking a mashup of the Rockwell and MD proposals might have born more fruit. At least not needed so much new hardware. Then traditional cylindrical tanks could have been used, and so composites could have been easier. And the shape could have been easier (if a tail-landing cylindrical shape like the MD vs. the airplane shape of the Rockwell). RS-25's could perhaps have been used, instead of the new aerospike. It looks like both the MD and Rockwell used it...or something that looks a lot like it.The Rockwell X-33 was the most conservative design and likely would have worked.I think being so conservative it even reused the STS orbiter OML might have made it seem too primitive.Ironic considering the CEV ten years later settled on the very conservative Apollo OML even though better performing shapes were well understood.
Ahhh. This again is where I'd like to have seen a Rockwell body on the MD vertical landing platform. Loose the wings, loose the wheels, but have the more simple cylindrical shape instead of the full sloping biconic. Although, I think the biconic "flies" better with aft paddle flaps which I think MD's design had. But I'd think a cylinder could be steered in the same manner with some development. And the geometry you are putting tanks in and fitting a TPS system to becomes much more simple.
But the whole idea/program was aimed at "proving" various high-tech systems for a 'future' SSTO so going with the MOST bleeding-edge proposal was a given from the start Despite a lot of the 'hype' inside and outside of NASA the plain truth was there was never any intention of having an operational vehicle, it was always going to be JUST a technology demonstrator. (Although I don't think I'm the only one that noticed the "instrument" payload bay was sized to fit something that looked a lot like it could fit the proposed "upper-stage" of the RASCAL proposal as long as the X-33 could meet the original proposed goals. Once LM started falling short the AF lost interest really quickly )
TSTO actually makes much more sense than SSTO despite the "fact" that a single stage would in theory be easier and cheaper to 'turn' than two stages but the right architecture (robust and rapidly reusable first stage specifically) would allow ramping up the flight rate quicker and with more payload from the start than any SSTO system. (A good case can be made for the "right" 1.5-STO as well )
Trying to get SSTO all in one swallow is a much more difficult task. A design for SSTO that I kinda like as having potential anyway...is a duel fuel cycle engine, with a triple cylindrical tank with two common bulkheads. RP-1, LOX, and LH2 (LOX in the middle, LH2 on top, RP-1 on the bottom). The engine can transition to kerolox to hydrolox during ascent. This seems like it would be the best mix of booster power while having good fuel density (so the craft isn't so big), and good performance at vacuum. The engine could have been a technological hold up however, I'm not sure how difficult an engine capable of such a transition would be, but it seemed a pretty novel concept. You essentially have a TTSO performance while being SSTO. And although it might be a bit of an expensive engine, you get it back and can reuse it.
Quote from: Lobo on 06/29/2015 10:39 pmTrying to get SSTO all in one swallow is a much more difficult task. A design for SSTO that I kinda like as having potential anyway...is a duel fuel cycle engine, with a triple cylindrical tank with two common bulkheads. RP-1, LOX, and LH2 (LOX in the middle, LH2 on top, RP-1 on the bottom). The engine can transition to kerolox to hydrolox during ascent. This seems like it would be the best mix of booster power while having good fuel density (so the craft isn't so big), and good performance at vacuum. The engine could have been a technological hold up however, I'm not sure how difficult an engine capable of such a transition would be, but it seemed a pretty novel concept. You essentially have a TTSO performance while being SSTO. And although it might be a bit of an expensive engine, you get it back and can reuse it.https://en.wikipedia.org/wiki/RD-701
Antilope7724
X-33 by Lockheed Martin above Earth - Computer Graphic (NASA-DFRC)https://archive.org/details/NIX-EC96-43631-9
Due to a spaceplane article in work, decided now was a good time to repair the article from 2006 on the X-33.https://www.nasaspaceflight.com/2006/01/x-33venturestar-what-really-happened/
Quote from: Chris Bergin on 07/11/2016 11:50 amDue to a spaceplane article in work, decided now was a good time to repair the article from 2006 on the X-33.https://www.nasaspaceflight.com/2006/01/x-33venturestar-what-really-happened/I cite this article all the time whenever a post comes up on various sites about the X-33 and what happened to it / why don't we do it now. Thanks for fixing it!