"SpaceShipTwo could be single stage to SUBorbit"
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From: Pat Flannery on 17 May 2010 19:21 On 5/17/2010 11:05 AM, Jeff Findley wrote: >> They are going to take a crack at getting one up to Mach 6.5 shortly: >> http://spaceflightnow.com/news/n1005/16waverider/ > > Make that Mach 4 to Mach 6.5. To get to Mach 4, the test vehicle is boosted > to speed by a solid rocket stage. Because of the choice of fuel, and lack > of sufficient TPS, and etc. this vehicle won't get anywhere near the Mach 25 > required for an orbital vehicle. In the big scheme of things, this is still > a research project, but if it is successful, I'm sure a follow-on research > vehicle will be built to expand the flight envelope even further. I think this one is more along the lines of a prototype hypersonic cruise missile than a test vehicle, since they intend to build four of them. > Practical air breathing hypersonic engines are still "just a few years > away", which is where they've been for decades. The big problem was that everyone knew that scramjet technology would be very expensive to develop, so they kept putting off developing it as long as possible, in favor of weapons delivery by stealth aircraft and missiles. There's a 30 page PDF of past work on scramjets by various countries here: http://ftp.rta.nato.int/public//PubFullText/RTO/TR/RTO-TR-AVT-007-V2///TR-AVT-007-V2-01.pdf Although it hasn't been highly funded, interest in the concept goes way back, and I think stealth sort of put it on the back burner for quite a while. Now that stealth is getting to be old hat, and everyone is figuring out ways to defeat it - like bistatic radar - the scramjet propulsion concept may be forced on them, costly or not. Of course the problem is the ignition speed need to get the thing operating - you ideally would have a engine that started off as a jet, turned into a ramjet, then converted into a scramjet, and finally ended up as a rocket. About the only concept I've heard of that could do something even a little like that is the ducted rocket. Pat
From: Dr J R Stockton on 17 May 2010 15:04 In sci.space.history message <4befef29$0$13586$c3e8da3(a)news.astraweb.com >, Sun, 16 May 2010 23:12:07, Sylvia Else <sylvia(a)not.at.this.address> posted: >How long would an SSME run on the hydrogen in Hindenburg? http://en.wikipedia.org/wiki/Hindenburg_class_airship ; "200,000 cubic metres of gas" http://en.wikipedia.org/wiki/Space_Shuttle_external_tank : "LH2 tank 1,497,440 l" and http://www.kayelaby.npl.co.uk/toc/ should enable it to be worked out. -- (c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05 MIME. Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
From: Alain Fournier on 17 May 2010 21:40 Dr J R Stockton wrote: > In sci.space.history message <4befef29$0$13586$c3e8da3(a)news.astraweb.com > >>, Sun, 16 May 2010 23:12:07, Sylvia Else <sylvia(a)not.at.this.address> > > posted: > > >>How long would an SSME run on the hydrogen in Hindenburg? > > > http://en.wikipedia.org/wiki/Hindenburg_class_airship ; "200,000 cubic > metres of gas" > > http://en.wikipedia.org/wiki/Space_Shuttle_external_tank : "LH2 tank > 1,497,440 l" > > and http://www.kayelaby.npl.co.uk/toc/ should enable it to be worked > out. I think the Hindenburg used gaseous hydrogen and that the Shuttle uses liquid hydrogen but I didn't see the density of hydrogen, liquid or gaseous in there. A cubic metre being 1000 litre, the Hindengurg has a volume about 133 times that of the Shuttle LH2 tank. The density of hydrogen at 101 kPa and 0 �C is 0.0899 g/l. The density of liquid hydrogen is 70 g/l, about 780 times that of gaseous hydrogen. So the Shuttle uses about 6 times more hydrogen that the Hindenburg. From the above I conclude that the Shuttle must go about 6 times faster than the Hindenburg :-) Alain Fournier
From: Sylvia Else on 18 May 2010 00:26 On 18/05/2010 11:40 AM, Alain Fournier wrote: > Dr J R Stockton wrote: > >> In sci.space.history message <4befef29$0$13586$c3e8da3(a)news.astraweb.com >> >>> , Sun, 16 May 2010 23:12:07, Sylvia Else <sylvia(a)not.at.this.address> >> >> posted: >> >> >>> How long would an SSME run on the hydrogen in Hindenburg? >> >> >> http://en.wikipedia.org/wiki/Hindenburg_class_airship ; "200,000 cubic >> metres of gas" >> >> http://en.wikipedia.org/wiki/Space_Shuttle_external_tank : "LH2 tank >> 1,497,440 l" >> >> and http://www.kayelaby.npl.co.uk/toc/ should enable it to be worked >> out. > > I think the Hindenburg used gaseous hydrogen and that the Shuttle > uses liquid hydrogen but I didn't see the density of hydrogen, liquid or > gaseous in there. A cubic metre being 1000 litre, the Hindengurg has > a volume about 133 times that of the Shuttle LH2 tank. > > The density of hydrogen at 101 kPa and 0 �C is 0.0899 g/l. > The density of liquid hydrogen is 70 g/l, about 780 times that > of gaseous hydrogen. So the Shuttle uses about 6 times more > hydrogen that the Hindenburg. > > From the above I conclude that the Shuttle must go about 6 times > faster than the Hindenburg :-) Can we calculate the relative safety? Sylvia.
From: Pat Flannery on 18 May 2010 05:06
On 5/17/2010 5:40 PM, Alain Fournier wrote: > > From the above I conclude that the Shuttle must go about 6 times > faster than the Hindenburg :-) Long time back, a friend and I were designing future dirigibles powered by solar energy derived from lightweight solar cells covering their exterior (during daylight some of the electrical power would be used to break down water into hydrogen and oxygen; at night these would be recombined in fuel cells to allow the electric motors to continue to drive the airship). As part of that project, I started looking up installed horsepower on airships of various sizes required to move them at various speeds, and made a most interesting finding...as the size of the airship increases, it takes proportionally less horsepower to move it at the same speed. To give you some idea of just how efficient a large airship can be in horsepower usage, the Hindenburg's total installed horsepower(4,800 hp) was _less than half_ of that of a single NK-12 turboprop engine off of a Tu-95 "Bear" bomber (12,000 ehp), yet could drive the 803-foot-long airship at 85 mph. Pat |