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Cost of launch and laws of physics
A couple of months ago Wired Magazine quoted John Pike as saying,
"It costs $10,000 a pound to get into space, and the reason isn't the government - it's physics." A lot of people here devoted many postings to ridiculing this comment. Some were not content to refute the statement and also questioned Pike's credentials, political ideology, and intellect. The comment was an off-the-cuff exaggeration, but one interpretation of it is true enough. Of course there is no physics equation that produces $10,000 per pound or any other value for the cost of launch. What is true is that the organization that actually launch things into space (NASA, Boeing, the Russians, etc.) don't just spend tons of money on bureaucracy. Rather, they also spend tons of money coping with laws of physics. It's not like Coca-Cola, which could be 20 times cheaper if it were just the syrup and no marketing. Launching a rocket into orbit takes talented engineers, special materials, and painstaking inspections, because usefully travelling at 12,000 miles an hour is really hard. Think how much harder it is to build a car that goes 120 mph than a bicycle that goes 12 mph. Now think how much harder it is build a jet that goes 1,200 mph than a car. Now take it one step further and you've got the difficulty of manned spaceflight. Of course doing any of these in expendable, unmanned form is much easier, which is part of the reason that most space rockets are expendable and unmanned. The flip side of this is that many of the CATS/RLV/X-Prize believers don't seem to take the laws of physics very seriously. For example, another Wired article quotes Gary Hudson as follows: "That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No." Given what happened to the space shuttle Columbia, that is a fair question. Just calling the answer counterintuitive and remarkable doesn't make it right. Okay, I imagine that someone will tell me that I'm quoting out of context. So here is the context: That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No. During the long climb into orbit, the atmosphere steadily decreases in density. The Roton starts out at very low speeds in the high-density atmosphere. As it picks up speed and climbs higher, the atmosphere thins out. The "dynamic pressure" (think wind) would actually be lower for the Roton than for many high-performance aircraft, including fighters. During reentry, the Roton would encounter a pretty benign environment as well. The Roton would start out at high speeds, but the atmosphere would be very thin. As the atmosphere becomes more dense at lower altitudes, the rotor would slow the vehicle down. Also, the load on the blades would be rather small because most of the propellant would have been consumed - meaning more than 90 percent of the overall weight would be gone. Wind tunnel tests have shown the heating would be no worse than that experienced by the space shuttle or other reentry vehicles. The heating would be "no worse" than that experienced by the space shuttle? Hmm... -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
#2
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Cost of launch and laws of physics
(Greg Kuperberg) writes:
A couple of months ago Wired Magazine quoted John Pike as saying, "It costs $10,000 a pound to get into space, and the reason isn't the government - it's physics." A lot of people here devoted many postings to ridiculing this comment. Some were not content to refute the statement and also questioned Pike's credentials, political ideology, and intellect. John Pike has no qualifications to make this claim. Note that even on his own, self promoting, web page, he makes no mention of any degrees or any real experience that would qualify him to make such a claim. http://www.globalsecurity.org/org/staff/pike.htm Others on John Pike's staff (http://www.globalsecurity.org/org/staff/index.html) hold degrees in: 1. Masters Degree (D.E.A.) in Political Studies 2. Bachelors Degree in International Studies (Masters Candidate Security Policy Studies ) 3. Bachelor of Arts degree 4. degree in International Service 5. Ph.D. in chemistry from Lehigh University in 1984 for the study of tissue lytic proteins produced by the human pathogen Vibrio vulnificus, a microorganism responsible for a type of "flesh-eating" disease in those with compromised immune systems 6. Associate of Applied Science degree in Mechanical Engineering Technology 7. Masters Degree in History None of these people has a background that would qualify them to make the statement that Pike made. The comment was an off-the-cuff exaggeration, but one interpretation of it is true enough. I don't think so. There was nothing in the statement that indicated that he was exaggerating. The flip side of this is that many of the CATS/RLV/X-Prize believers don't seem to take the laws of physics very seriously. For example, another Wired article quotes Gary Hudson as follows: "That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No." Given what happened to the space shuttle Columbia, that is a fair question. Just calling the answer counterintuitive and remarkable doesn't make it right. Anyone with any qualifications would know that what Gary said is true. Roton would have been mostly empty tankage. As such, the heating it experiences on re-entry would be much less than the much more dense shuttle (which drops its large, empty tank before reaching orbit). Roton would do much of its decelleration very high in the atmosphere where the dynamic pressure is low. The shuttle, being very dense, simply can't. It's apples and oranges to anyone who understands a bit of the physics (something that Pike clearly does not understand). Jeff -- Remove "no" and "spam" from email address to reply. If it says "This is not spam!", it's surely a lie. |
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Cost of launch and laws of physics
Greg, it's mostly nothing to do with physics; it's economics. It's more
to do with the low market size right now; which in turn is to do with the current high cost. It's catch 22. The price is too high, so practically nobody goes. Because nobody goes, the costs stay high (development costs don't amortise away, unit costs stay high, production costs stay high.) It's not that you don't need 10,000 people to go into space, it's just that if you only send 4 rockets into space with those 10,000 people, then it costs 2.7x more than if you send 16 rockets into space with, say, 15,000 people. Basically, rockets are currently mostly built by hand, one off. That's expensive. Production lines are cheaper. The Russians use more production line techniques, and their rockets are about 1/4 the cost of other people. (It has been very, very frequently suggested that low wages are the reason for this, but people who have gone to Russia report that it turns out that that only accounts for some, but not all of the differences; Russian rockets are 1/2 the cost even allowing for this, strangely enough the laws of physics are the same in Russia as elsewhere). Physics definitely has a part to play though; it's just that that isn't the dominant force that keeps the price high as it is right now. |
#4
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Cost of launch and laws of physics
"Greg Kuperberg" wrote in message ... Think how much harder it is to build a car that goes 120 mph than a bicycle that goes 12 mph. Now think how much harder it is build a jet that goes 1,200 mph than a car. Now take it one step further and you've got the difficulty of manned spaceflight. Of course doing any of these in expendable, unmanned form is much easier, which is part of the reason that most space rockets are expendable and unmanned. Build or design? Design can be costly, but once designed, building is just bending metal. Compare how much manpower the Russians spend on producing a Soyuz or Proton compared to say an American Atlas or Delta. Then compare the infrastructure required to launch it. Completely comparing salaries (since that's a tough one to compute) you'll find if we build rockets the way the Russians do, they'd be cheaper by quite a bit. The flip side of this is that many of the CATS/RLV/X-Prize believers don't seem to take the laws of physics very seriously. For example, another Wired article quotes Gary Hudson as follows: "That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No." Given what happened to the space shuttle Columbia, that is a fair question. Just calling the answer counterintuitive and remarkable doesn't make it right. No, but it IS right. The answer IS counterintuitive and remarkable. I don't see where you argument is other than he didn't explain WHY it's counterintuitive and remarkable. Which, given the context, he appears to have done. So, I have no clue what point you're making here. Okay, I imagine that someone will tell me that I'm quoting out of context. So here is the context: -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
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Cost of launch and laws of physics
On Wed, 06 Aug 2003 00:24:36 GMT, in a place far, far away, "Greg D.
Moore \(Strider\)" made the phosphor on my monitor glow in such a way as to indicate that: The flip side of this is that many of the CATS/RLV/X-Prize believers don't seem to take the laws of physics very seriously. For example, another Wired article quotes Gary Hudson as follows: "That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No." Given what happened to the space shuttle Columbia, that is a fair question. Just calling the answer counterintuitive and remarkable doesn't make it right. No, but it IS right. The answer IS counterintuitive and remarkable. I don't see where you argument is other than he didn't explain WHY it's counterintuitive and remarkable. Which, given the context, he appears to have done. So, I have no clue what point you're making here. Sadly, I suspect that he doesn't either. He should perhaps expand his expertise beyond mathematics before embarassing himself further. -- simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole) interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org "Extraordinary launch vehicles require extraordinary markets..." Swap the first . and @ and throw out the ".trash" to email me. Here's my email address for autospammers: |
#6
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Cost of launch and laws of physics
In article ,
Greg D. Moore \(Strider\) wrote: "That leaves the most frequently asked question about the Roton: wouldn't the rotor blades burn off in the atmosphere? The remarkable - and counterintuitive - answer is No." Given what happened to the space shuttle Columbia, that is a fair question. Just calling the answer counterintuitive and remarkable doesn't make it right. No, but it IS right. The answer IS counterintuitive and remarkable. I don't see where you argument is other than he didn't explain WHY it's counterintuitive and remarkable. Which, given the context, he appears to have done. What he said in context was, first, that re-entry would be a "pretty benign" environment, and second, that it would be "no worse" than what the shuttle experiences. But as the destruction of STS-107 makes clear, the shuttle's environment during re-entry is not remotely benign. People in this thread said something rather different from the Hudson quote: that the Roton blades would encounter an environment which is much more benign than shuttle re-entry, not "no worse". Now STS-107 broke apart at 210,000 feet moving at Mach 18. How fast is the Roton supposed to go at that altitude, and what are the helicopter blades supposed to do then? If they are retracted entirely, at what altitude and velocity are they supposed to deploy? Taking the laws of physics seriously requires clear answers to questions like this. Even answers to within a factor of 2 would be a start. -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
#8
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Cost of launch and laws of physics
Greg Kuperberg wrote:
What he said in context was, first, that re-entry would be a "pretty benign" environment, and second, that it would be "no worse" than what the shuttle experiences. But as the destruction of STS-107 makes clear, the shuttle's environment during re-entry is not remotely benign. People in this thread said something rather different from the Hudson quote: that the Roton blades would encounter an environment which is much more benign than shuttle re-entry, not "no worse". Now STS-107 broke apart at 210,000 feet moving at Mach 18. How fast is the Roton supposed to go at that altitude, and what are the helicopter blades supposed to do then? If they are retracted entirely, at what altitude and velocity are they supposed to deploy? Taking the laws of physics seriously requires clear answers to questions like this. Even answers to within a factor of 2 would be a start. Re-entry vehicles other than ballistic missile RVs have a hot side and a cooler side. Well, even RVs have a cooler spot on the back, but it's not very big. The 'front side' of the shuttle has very high temperature exposed edges (leading edges, RCC panels) and moderately high temperature large surface areas (black tiles). The 'back side' of the shuttle has moderately low to fairly low temperature areas. Some of the areas are protected by essentially flexible quartz fabric blankets, and experience no more peak temperature or temperature duration than is seen cooking a posteak on the barbequeue. The insulation is required primarily because Aluminum's high temperature tolerance is terrible; if the upper surfaces were made of steel or titanium you could get away without insulating them, just making sure that heat leaking in didn't fry wiring or hydraulics inside, etc. In the Roton vehicle design, the base reenters first, and has the high heat loading areas. The hypersonic aerodynamics mean that the hot high temperature gas flows off with the primary shockwave, and stays well away from the sides of the vehicle. Though the environment at the sides of the vehicle, and at the top and out where the rotors would be, is pretty hot, it's like what you see on the back side of the shuttle. Not 'melt everything not covered in RCC, tiles, or ablator' hot; cool enough that inconel and other high temperature alloys will be fine, at least. -george william herbert |
#9
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Cost of launch and laws of physics
"Greg Kuperberg" wrote:
Think how much harder it is to build a car that goes 120 mph than a bicycle that goes 12 mph. Now think how much harder it is build a jet that goes 1,200 mph than a car. Now take it one step further and you've got the difficulty of manned spaceflight. Of course doing any of these in expendable, unmanned form is much easier, which is part of the reason that most space rockets are expendable and unmanned. Pffft. It costs next to nothing to build a car that can go 120 mph, probably only about the same cost as a decent bicycle (few hundred dollars). It costs a lot of money to make a nice car though, and by the standards of "physics", all modern cars are nice. A simple engine powered vehicle with 4 wheels is a far cry from today's automobiles. And, for example, building a model-T type car (let alone something simpler) would be much cheaper than any car now on the market. When was the last time you saw a new car without an upholstered interior, power brakes, power steering, a windshield, windows, full suspension, a heater, a speedometer, headlights, signaling lights, brake lights, an automatic starter, a battery, or an alternator? Not recently I'd bet. But none of those things are strictly required to go 120 mph or even 40 mph. Cars are cheap now because we've had so much experience building them and we know how to do it very well, and also because the market has grown so large that overhead costs in the billions (a typical cost range for design and production line setup for a modern car) are amortized to near nothing per car among so many buyers. If we'd started off in the late 1800s thinking that the only way to make a car was to festoon it with fancy, expensive googaws then we'd have never had the cost breakthrough that led to automobile ownership being widespread and fairly inexpensive. The same thing is the case for spaceflight, I believe. We have these one of a kind, custom built luxury vehicles which are too expensive to open up the spaceflight market much (manned or unmanned). What we need is a simple model-T that does the job and is cheap, though not necessarily the finest of its class. But, once lots of people or companies buy the model-T and use it that will create the more broad based market which will be capable of pushing development at a much faster pace than the hand-buil, custom model production lines can, and thus we will end up with better, less expensive launch vehicles in the long run, due to expansion of the market. As I said, it happened with automobiles; it also happened with computers and audio/video electronics, and much else. |
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Cost of launch and laws of physics
"Christopher M. Jones" wrote in message ... The same thing is the case for spaceflight, I believe. We have these one of a kind, custom built luxury vehicles which are too expensive to open up the spaceflight market much (manned or unmanned). What we need is a simple model-T that does the job and is cheap, though not necessarily the finest of its class. But, once lots of people or companies buy the model-T and use it that will create the more broad based market which will be capable of pushing development at a much faster pace than the hand-buil, custom model production lines can, and thus we will end up with better, less expensive launch vehicles in the long run, due to expansion of the market. As I said, it happened with automobiles; it also happened with computers and audio/video electronics, and much else. But not with supersonic passenger aircraft. :-/ Low costs and mass production are fine if the market exists, I'm personally very dubious about the space tourism angle and without that the market opportunities for mass production are relatively limited. I recently flew Concorde which was full, but mostly of aviation enthusiasts like me who had had a chance at a low cost ticket, all of us were pretty much at the limit of what our partners would allow us to spend on a one-off treat. Still, the low cost approach seems to have worked with Concorde, it is fully booked pretty much until they stop flying it. That's not to say that I think Virgin could run it profitably. I got some incredible pictures out of the window at 58,000 feet which, sadly, probably about as high as I expect to ever get to fly. |
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