A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Pat Flannery on 4 Apr 2010 18:00 On 4/4/2010 10:04 AM, Craig Bingman wrote: > > The density of liquid deuterium is 162 kilograms per cubic meter > The density of liquid hydrogen (H2) is 71 kilograms per cubic meter > > So it is slightly more dense per mole. However, dragging along more mass in the > tank isn't the issue... If you filled the tank with hydrogen and some rocks, the > tank would contain more mass, but no more energy. > > There is another small effect in favor of D2 (I can't believe I'm even > saying this, given how much deuterium costs) and that is that its enthalpy of > formation is slightly more energetic than H2. -246 vs -239 kJ/mol. > > Since hydrogen oxygen engines achieve their high specific impulse at least in part > by running very fuel rich, and lowering the effective molecular weight of the > exhaust with a lot of excess H2, one would think that there would be a big > hit with deterium fueled engines. (Ve)2 is inversely proportional to the > molecular weight of the exhaust. > > Seems like a big hit in Isp for a small increase in density. In the article, they state that they were just looking into all possible propellant combos, and not seriously suggesting the liquid deuterium/liquid fluorine mix for it. Besides the extremely high cost of the liquid deuterium, the liquid fluorine was nasty enough that anyone who played with it as a rocket propellant quickly gave up on it despite the high isp: http://www.astronautix.com/props/lf2lh2.htm Pat
From: J. Clarke on 4 Apr 2010 15:33 On 4/4/2010 1:04 PM, Craig Bingman wrote: > In article<Of2dnetOKofmhCXWnZ2dnUVZ_gadnZ2d(a)posted.northdakotatelephone>, > Pat Flannery<flanner(a)daktel.com> wrote: >> On 4/3/2010 5:17 PM, Craig Bingman wrote: >>> >>> Hi Pat, >>> >>> I don't understand how deuterium would help at all. It weighs twice as much, >>> it has no more enthalpy of combustion, and i would think that the increased >>> mass of deuterium would hurt specific impulse by increasing the effective >>> molecular weight of the exhaust. >>> >>> Can you or someone else give me a reality check on that one? >> >> Here's the article where that combo is mentioned, that came out well >> before April 1st: >> http://www.thespacereview.com/article/1591/1 >> The part before that mentions the problems with fluorine: >> http://www.thespacereview.com/article/1580/1 >> According to one poster to this thread, the advantage liquid deuterium >> gives you is that it's a lot more dense by volume than standard liquid >> hydrogen, so you can decrease the size of your fuel tanks for the same >> amount of energy content. > > The density of liquid deuterium is 162 kilograms per cubic meter > The density of liquid hydrogen (H2) is 71 kilograms per cubic meter > > So it is slightly more dense per mole. However, dragging along more mass in the > tank isn't the issue... If you filled the tank with hydrogen and some rocks, the > tank would contain more mass, but no more energy. > > There is another small effect in favor of D2 (I can't believe I'm even > saying this, given how much deuterium costs) and that is that its enthalpy of > formation is slightly more energetic than H2. -246 vs -239 kJ/mol. > > Since hydrogen oxygen engines achieve their high specific impulse at least in part > by running very fuel rich, and lowering the effective molecular weight of the > exhaust with a lot of excess H2, one would think that there would be a big > hit with deterium fueled engines. (Ve)2 is inversely proportional to the > molecular weight of the exhaust. > > Seems like a big hit in Isp for a small increase in density. I wouldn't call more than doubling the density "a small increase". As for rocks, if the rocks are melted down, vaporized, and shot out the back at the same velocity as the hydrogen then your analogy would be valid. The problem being addressed is not putting more fuel in the tank, it is making the tank and its associated structure physically smaller. I'm too lazy to run the numbers on it and see how it would work out in practice. I suspect that it's much cost for no gain, like most such schemes, but I've been wrong before. > >
From: Robert Clark on 5 Apr 2010 15:29 On Mar 23, 12:57 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > On Mar 22, 2:53 pm, Pat Flannery <flan...(a)daktel.com> wrote: > > > ... The > > advantages of high altitude fueling and launch for a Shuttle type > > vehicle to avoid ice buildup on tankage using any sort of cryogenic > > propellants go clean back to the Air Force/DARPA ALSV concept that > > Dwayne Day is following the history of in The Space Review:http://www.thespacereview.com/article/1569/1http://www.thespacereview... > > Fluorine-deuterium? Oh, that will be cheap to use as fuel. ;-) > > > Pat > > Thanks for those links. > It has been rumored that the Air Force has tested such a system: > > Two-Stage-to-Orbit ''Blackstar'' System Shelved at Groom Lake? > Mar 5, 2006 > By William B. Scotthttp://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst... > > TSTO spaceplanes.http://robotpig.net/aerospace/en_tsto.php > > Did Pentagon create orbital space plane? > Magazine reports evidence for classified project, sparking some > skepticism. > By James Oberg, NBC News space analyst > updated 5:10 p.m. ET, Mon., March. 6, 2006http://www.msnbc.msn.com/id/11691989/ > The story that an air-launched spaceplane system had already been tested was generally skeptically received, despite the history of the concept as presented by Dwayne Day. But it is notable that the X-33 might be able to fulfill this role with the tank lightweighting methods discussed in the first post of this thread and by using a supersonic high altitude bomber. The story on the BlackStar system likened the carrier craft to the Mach 3 XB-70 Valkyrie bomber (has to be the all time best name for an aircraft): XB-70 Valkyrie. http://en.wikipedia.org/wiki/XB-70_Valkyrie However, the XB-70 was canceled having cost $1.5 billion in 1960's dollars for two prototypes. This would likely be in the range of $10 billion now with inflation. If doesn't seem likely the Air Force would be willing to spend that much just for craft that could only serve as the carrier vehicles. But it may be possible to use a much cheaper and (approximately) operational craft as the mother ship. I'm thinking of the original version of the B-1A Lancer supersonic bomber. Recall that the original B-1 was supposed to be Mach 2+ capable, and indeed some prototype vehicles were built with that capability: B-1 Lancer. http://en.wikipedia.org/wiki/B-1_Lancer#Development The 1975 cost of the B-1A supersonic version was $70 million per plane. There were additional ballooning costs to the program but these were probably due to the extensive and expensive electronic warfare avionics that had to be added as the Soviet Union's radar capabilities increased. These wouldn't be needed for this application. So we could estimate the cost as $70 million per plane in 1975 dollars. So, say, $280 million per plane in 2010 dollars. Certainly affordable. However, to get the X-33 to orbit even with air launch you would need to lighten the fuel tanks. In the first post of this thread I estimated that by using various lightweighting methods you could cut the tank weight of the X-33 by 9,200 lbs. See section II here: Newsgroups: sci.space.policy, sci.astro, sci.physics From: Robert Clark <rgregorycl...(a)yahoo.com> Date: Sun, 1 Nov 2009 05:20:13 -0800 (PST) Subject: A kerosene-fueled X-33 as a single stage to orbit vehicle. http://groups.google.com/group/sci.space.policy/msg/0b8b04a58b08278e?hl=en This would bring the dry weight from 63,000 to 53,800 lbs. Here I'm considering the X-33 being kept as hydrogen-fueled to keep the gross- mass low for this upper stage application. Note that the aerospike engines to be used on the X-33 weren't weight optimized having a T/W ratio of only 40 to 1, since their main purpose was to test the aerospike altitude compensation nozzles. However, for this application the launch will be at such high altitude, ca 60,000 ft, 20,000 m, that the engines will have effectively vacuum performance. Then in calculating the delta-V possible we'll use the vacuum Isp in calculating this. Possibilities for the engines might be a single shuttle main engine or two of the J-2 engines used on the Saturn V upper stages. This would reduce the engine weight from the current 15,000 lbs to 7,000 lbs. So the dry weight would become 45,800 lbs. Using the 210,000 lbs LH2/LOX propellant weight, the 45,800 dry weight, and a 453 s vacuum Isp, the X-33 could have a delta-V of 453*9.8*ln(1+210,000/45800) = 7,636 m/s. Now you can get 600 m/s from the Mach 2 carrier craft. This brings it to 8,236 m/s. You get around 462 m/s tangential velocity for free from launching near the equator so call the speed now 8,700 m/s. Now if we only require an altitude considered space of 100 km and the carrier craft already gives us 20 km altitude this could just barely give us sufficient delta-V for orbit. This delta-V would also be helped by using a "lifting ascent trajectory" mentioned in Day's articles: Fire in the sky: the Air Launched Sortie Vehicle of the early 1980s (part 1) by Dwayne Day Monday, February 22, 2010 http://www.thespacereview.com/article/1569/1 However, there is a question of the max take-off weight of the B-1, and how much of that could be fuel compared to payload. For this application used only for a short dash to high altitude at high speed were long range would not be needed, so therefore much less fuel load, could we strengthen the airframe as done for the 747 carrier craft for the shuttle so that B-1A could carry the ca. 270,000 lbs loaded weight of the X-33? Bob Clark
From: Robert Clark on 6 Apr 2010 10:38 On Apr 5, 3:29 pm, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > On Mar 23, 12:57 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote: > > > On Mar 22, 2:53 pm, Pat Flannery <flan...(a)daktel.com> wrote: > > > ... The > > > advantages of high altitude fueling and launch for a Shuttle type > > > vehicle to avoid ice buildup on tankage using any sort of cryogenic > > > propellants go clean back to the Air Force/DARPA ALSV concept that > > > Dwayne Day is following the history of in The Space Review:http://www..thespacereview.com/article/1569/1http://www.thespacereview... > > > Fluorine-deuterium? Oh, that will be cheap to use as fuel. ;-) > > > > Pat > > > Thanks for those links. > > It has been rumored that the Air Force has tested such a system: > > > Two-Stage-to-Orbit ''Blackstar'' System Shelved at Groom Lake? > > Mar 5, 2006 > > By William B. Scott >> http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst.... > > > TSTO spaceplanes.http://robotpig.net/aerospace/en_tsto.php > > > Did Pentagon create orbital space plane? > > Magazine reports evidence for classified project, sparking some > > skepticism. > > By James Oberg, NBC News space analyst > > updated 5:10 p.m. ET, Mon., March. 6, 2006 > > http://www.msnbc.msn.com/id/11691989/ > > The story that an air-launched spaceplane system had already been > tested was generally skeptically received, despite the history of the > concept as presented by Dwayne Day. But it is notable that the X-33 > might be able to fulfill this role with the tank lightweighting > methods discussed in the first post of this thread and by using a > supersonic high altitude bomber. > The story on the BlackStar system likened the carrier craft to the > Mach 3 XB-70 Valkyrie bomber (has to be the all time best name for an > aircraft): > > XB-70 Valkyrie. > http://en.wikipedia.org/wiki/XB-70_Valkyrie > > However, the XB-70 was canceled having cost $1.5 billion in 1960's > dollars for two prototypes. This would likely be in the range of $10 > billion now with inflation. If doesn't seem likely the Air Force would > be willing to spend that much just for craft that could only serve as > the carrier vehicles. > But it may be possible to use a much cheaper and (approximately) > operational craft as the mother ship. I'm thinking of the original > version of the B-1A Lancer supersonic bomber. Recall that the original > B-1 was supposed to be Mach 2+ capable, and indeed some prototype > vehicles were built with that capability: > > B-1 Lancer.http://en.wikipedia.org/wiki/B-1_Lancer#Development > > The 1975 cost of the B-1A supersonic version was $70 million per > plane. There were additional ballooning costs to the program but these > were probably due to the extensive and expensive electronic warfare > avionics that had to be added as the Soviet Union's radar capabilities > increased. These wouldn't be needed for this application. So we could > estimate the cost as $70 million per plane in 1975 dollars. So, say, > $280 million per plane in 2010 dollars. Certainly affordable. > However, to get the X-33 to orbit even with air launch you would need > to lighten the fuel tanks. In the first post of this thread I > estimated that by using various lightweighting methods you could cut > the tank weight of the X-33 by 9,200 lbs. See section II here: > > Newsgroups: sci.space.policy, sci.astro, sci.physics > From: Robert Clark <rgregorycl...(a)yahoo.com> > Date: Sun, 1 Nov 2009 05:20:13 -0800 (PST) > Subject: A kerosene-fueled X-33 as a single stage to orbit vehicle. > http://groups.google.com/group/sci.space.policy/msg/0b8b04a58b08278e?... > > This would bring the dry weight from 63,000 to 53,800 lbs. Here I'm > considering the X-33 being kept as hydrogen-fueled to keep the gross- > mass low for this upper stage application. > Note that the aerospike engines to be used on the X-33 weren't weight > optimized having a T/W ratio of only 40 to 1, since their main purpose > was to test the aerospike altitude compensation nozzles. However, for > this application the launch will be at such high altitude, ca 60,000 > ft, 20,000 m, that the engines will have effectively vacuum > performance. > Then in calculating the delta-V possible we'll use the vacuum Isp in > calculating this. Possibilities for the engines might be a single > shuttle main engine or two of the J-2 engines used on the Saturn V > upper stages. This would reduce the engine weight from the current > 15,000 lbs to 7,000 lbs. So the dry weight would become 45,800 lbs. > Using the 210,000 lbs LH2/LOX propellant weight, the 45,800 dry > weight, and a 453 s vacuum Isp, the X-33 could have a delta-V of > 453*9.8*ln(1+210,000/45800) = 7,636 m/s. Now you can get 600 m/s from > the Mach 2 carrier craft. This brings it to 8,236 m/s. You get around > 462 m/s tangential velocity for free from launching near the equator > so call the speed now 8,700 m/s. > Now if we only require an altitude considered space of 100 km and the > carrier craft already gives us 20 km altitude this could just barely > give us sufficient delta-V for orbit. This delta-V would also be > helped by using a "lifting ascent trajectory" mentioned in Day's > articles: > > Fire in the sky: the Air Launched Sortie Vehicle of the early 1980s > (part 1) > by Dwayne Day > Monday, February 22, 2010 > http://www.thespacereview.com/article/1569/1 > > However, there is a question of the max take-off weight of the B-1, > and how much of that could be fuel compared to payload. For this > application used only for a short dash to high altitude at high speed > were long range would not be needed, so therefore much less fuel load, > could we strengthen the airframe as done for the 747 carrier craft for > the shuttle so that B-1A could carry the ca. 270,000 lbs loaded weight > of the X-33? > As I mentioned in the section on lifting trajectories in the first post of this thread, you need a good lift/drag ratio at hypersonic speeds to get significant propellant savings using a lifting trajectory. See section IV here: Newsgroups: sci.space.policy, sci.astro, sci.physics From: Robert Clark <rgregorycl...(a)yahoo.com> Date: Sun, 1 Nov 2009 05:20:13 -0800 (PST) Subject: A kerosene-fueled X-33 as a single stage to orbit vehicle. http://groups.google.com/group/sci.space.policy/msg/0b8b04a58b08278e?hl=en The "Air Launched Sortie" vehicles discussed in Day's articles had such good ratios. However, for the X-33 it's as poor as for the space shuttle, only around 1 at hypersonic velocities. Then it's doubtful the lifting trajectory could make up for the delta-V shortfall for this air-launched X-33. But perhaps we could increase the propellant load. By reducing their respective temperatures down to near their freezing points, it's known you can increase the density of the LH2/LOX combination by about 10%. So let's say the propellant load is now 231,000 lbs. Using still the 45,800 lbs dry weight, and 453 s vacuum Isp, we get a delta-V of 453*9.8*ln(1+231,000/45800) = 7,987 m/s. Adding on the 600 m/s we get from the Mach 2 carrier craft and the 462 m/s we get from the Earth's rotation at the equator we have a total of 9,049 m/s delta-V. This is about right when you consider that for either the single SSME or dual J-2 engine option, the initial launch thrust/weight ratio will be high at nearly 2 to 1, which will result in lower gravity losses. However, in any case you would be able to carry only minimal payload. You might be able to carry 2 crew members with environmental systems. However, a problem still is the weight the B-1A would have to carry compared to its max takeoff weight. See the specifications here: B-1 Lancer. http://en.wikipedia.org/wiki/B-1_Lancer#Specifications_.28B-1B.29 The max takeoff weight of the B-1B is given as 477,000 lbs. If you subtract off the 231,000 lbs X-33 propellant load and 45,800 lbs X-33 dry weight that leaves 200,200 lbs. But the empty weight of the B-1B is 192,000 lbs, so only 8,000 lbs is left over for the B-1B fuel, and that does not even include the extra weight that would need to be added to add strength to the airframe to support the much higher payload. One possible way you could reduce the strengthening mass is an idea used with rockets: the propellant tank being pressurized can help to support both compressive and bending loads that normally would require extra strengthening mass. Then by placing the fuel tank for the B-1A in the fuselage rather than the wings, which is possible because you no longer need bomb bays, you might be able to solve the problem of extra strengthening mass. However, another problem is that the B-1A actually had a lower max takeoff weight than the B-1B, while also a lower empty weight. You would need to find a way to give the B-1A the same max takeoff weight as the B-1B while maintaining its Mach 2+ top speed. Another solution would not be as palatable to the Air Force. The Russians currently have in actual operation a Mach 2 bomber that is larger than the B-1: Tupolev Tu-160. http://en.wikipedia.org/wiki/Tupolev_Tu-160 It has a max takeoff weight of 606,000 lbs and an empty weight of 242,000 lbs. That leaves 364,000 lbs left over. That would be well in excess of what's needed to carry the X-33 and even give it a significant payload, and for the Tupolev to still have a significant fuel load. The design of the X-33 lifting body airframe was not particularly advanced once you get by the problem of lightweighting the tanks, which I have given some methods to solve. The most advanced characteristic of the vehicles design were the aerospike engines, and these would not even be needed for this air launched application. Note also the other competing proposals for the X-33 suborbital demonstrator by Rockwell and McDonnell-Douglas were about the same in size and capabilities as the selected Lockheed version, but these would offer no complications at all in getting the tanks to have the needed lightweight character since they were of circular cross- section. Then it would not be difficult at all for the Russians to make such a X-33 class spaceplane. And they already have the carrier craft to serve as its launch platform to orbit. Bob Clark
From: hcobb on 7 Apr 2010 00:42
The fix is to get your air launched rocket into space, but not into orbit. It's a Virgin Galactic style shot that just clears the atmosphere at roughly zero velocity. Then bring in stream of tiny impactors at 60 km/s to power an ablative rocket and off you go. At 60 km/s these impactors have 400 times the energy their mass in TNT would provide so this is far more energetic than any chemical rocket could manage. Where do you get the 60 km/s? Simply launch the micro-impactors clear of the Earth and have them slingshot around the Earth a half dozen times to flip the planes of their orbits around until they're counterorbital with respect to the Earth and you double Earth's roughly 30 km/s orbital speed for the impact. -HJC |