"SpaceShipTwo could be single stage to SUBorbit"
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From: J. Clarke on 14 May 2010 08:40 On 5/13/2010 11:12 PM, Greg D. Moore (Strider) wrote: > J. Clarke wrote: >> >> Scramjets work. Get used to it. > > Really? How many flight hours do they have? Enough to show that they work. > How many have been flown more than once? Enough to show that they work.
From: J. Clarke on 14 May 2010 08:44 On 5/14/2010 12:05 AM, Jorge R. Frank wrote: > On 05/13/2010 05:08 PM, J. Clarke wrote: >> On 5/13/2010 4:04 PM, Jeff Findley wrote: >>> "Pat Flannery"<flanner(a)daktel.com> wrote in message >>> news:6vGdnRW146eIxXHWnZ2dnUVZ_tOdnZ2d(a)posted.northdakotatelephone... >>>> On 5/13/2010 9:10 AM, LSMFT wrote: >>>>> What happened to the X-30? >>>> >>>> And since when did 50,000 feet become outer space? >>>> I like the part about it using a "liquid chemical propulsion system", >>>> without specifying what those chemicals are exactly. >>>> You could certainly make a ground takeoff rocket plane that could >>>> climb to >>>> 50,000 feet, but since numerous types of jet aircraft are capable of >>>> flying to 50,000 feet also, what would be the point of doing this? >>> >>> The promises made by X-30 were absolutely silly, in retrospect. A >>> vehicle >>> which can cruise at hypersonic speeds is going to be very different >>> than a >>> vehicle which can accelerate to orbital speeds, yet somehow X-30 was >>> being >>> sold as able to do both (makes me think of the SNL skit for Shimmer, a >>> floor >>> polish and a dessert topping). >> >> So let's see, a vehicle that can cruise at Mach 20 is going to be >> different from one that can accelerate to Mach 25 how, exactly? > > If you haven't figured it out on your own, it is not going to be worth > anyone's time to explain it to you. But the quick-and-dirty is that > cruising at Mach 20 with an airbreather is going to require remaining at > an altitude where there is enough O2 to keep the engine going, which > radically increases the total heat load. Which heat load goes into the fuel and out the exhaust. > Whereas a Mach 25 accelerator > will only spend a brief amount of time in the Mach region where a > scramjet will do any good, so it will need two additional propulsion > systems: one to accelerate to the minimum speed to light the scramjet, > another (necessarily rocket-based) to take over for the final boost to > orbit once the scramjet is useless. The additional weight of having > three propulsion systems more than outweighs the advantages of the > airbreather. You seem to have missed the point. > IMO scramjets are daft for either mission. It's at times like this that > I really miss Henry Spencer. He could explain this far more eloquently > than I could. So what do you recommend for Mach 20 cruise if scramjets are "daft" for it?
From: J. Clarke on 14 May 2010 08:42 On 5/13/2010 11:14 PM, Greg D. Moore (Strider) wrote: > J. Clarke wrote: >>> X-30 was way too much for NASA to do in one huge leap and would have >>> required billions more dollars just to try to make it work. The >>> state of the art in hypersonic propulsion still isn't where it would >>> need to be to build X-30 today (note that X-30 was cancelled more >>> than two decades ago). Hypersonic propulsion is one of those >>> promising looking technologies that's been "only a few years away" >>> for many decades. >> >> Uh, it's not there because Clinton pulled the plug on it. > > Really? Amazing. I didn't realize Clinton whas that powerful. You mean no > one else was capable of doing research on Hypersonic propulsion? Nobody is capable of doing any kind of research on anything unless somebody is willing to put food on their table while they're doing it. > Hypersonic propulsion was " a few years away" before Clinton and is still a > few years away. So where would it be if development had been continued instead of being stopped and restarted again a decade or so later?
From: Greg D. Moore (Strider) on 14 May 2010 09:08 J. Clarke wrote: > On 5/13/2010 11:12 PM, Greg D. Moore (Strider) wrote: >> J. Clarke wrote: >>> >>> Scramjets work. Get used to it. >> >> Really? How many flight hours do they have? > > Enough to show that they work. > >> How many have been flown more than once? > > Enough to show that they work. Umm, really? I don't know of any that have flown for more than a few minutes at my most recent research didn't reveal any that were reflown. But as you seem to know, perhaps you can point me to the ones that have flown for hours. And the ones that have reflown. -- Greg Moore Ask me about lily, an RPI based CMC.
From: Greg D. Moore (Strider) on 14 May 2010 09:10
J. Clarke wrote: > On 5/13/2010 11:14 PM, Greg D. Moore (Strider) wrote: >> J. Clarke wrote: >>>> X-30 was way too much for NASA to do in one huge leap and would >>>> have required billions more dollars just to try to make it work. The >>>> state of the art in hypersonic propulsion still isn't where it >>>> would need to be to build X-30 today (note that X-30 was cancelled >>>> more than two decades ago). Hypersonic propulsion is one of those >>>> promising looking technologies that's been "only a few years away" >>>> for many decades. >>> >>> Uh, it's not there because Clinton pulled the plug on it. >> >> Really? Amazing. I didn't realize Clinton whas that powerful. You >> mean no one else was capable of doing research on Hypersonic >> propulsion? > > Nobody is capable of doing any kind of research on anything unless > somebody is willing to put food on their table while they're doing it. > >> Hypersonic propulsion was " a few years away" before Clinton and is >> still a few years away. > > So where would it be if development had been continued instead of > being stopped and restarted again a decade or so later? Again, it wasn't stopped worldwide. Clinton wasn't that powerful. Other countries DID do research and development in the meantime. Or are you saying only R&D in the US is applicable? -- Greg Moore Ask me about lily, an RPI based CMC. |