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SpaceX Dragon
Per SpaceX, the Dragon capsule carries 1200 kg propellant, which
"supports a safe mission profile from sub-orbital insertion to ISS rendezvous to reentry." Questions: 1. What is the propellant? 2. Why the reference to "sub-orbital" insertion? Falcon 9 would perform full orbital insertion. Is that a back-up capability provided in the event of sub-nominal performance of the launch vehicle? I'd have thought that the Furthermore, the second Dragon mission is intended to demonstrate rendezvous with the Falcon 9's second stage, suggesting that at least on that mission, the second stage will make it all the way to orbit. 3. SpaceX used to claim that both stages of the Falcon 9 would be reusable, though it was never clear to me precisely how the upper stage was to be recovered. I see no mention of re-usability on the website now. Has re-usability been dropped? |
#2
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SpaceX Dragon
Have I received no replies because my questions are too stoopid or
because nobody knows? |
#3
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SpaceX Dragon
OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a relatively toxic propellants like that? The same site says that both stages are to be recovered by parachute. Coulda guessed that -- but what about the other details of bringing the second stage back from orbit? |
#4
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SpaceX Dragon
are wrote: OK, spaceglobal.com says the propellant is MMH/NTO, same as for the attitude-control system. Isn't it a bit 20th-century to be using a relatively toxic propellants like that? The same site says that both stages are to be recovered by parachute. Coulda guessed that -- but what about the other details of bringing the second stage back from orbit? They've been keeping details pretty close to their chest, which is probably pretty wise. http://www.thespacereview.com/article/682/1 http://en.wikipedia.org/wiki/SpaceX Pat |
#5
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SpaceX Dragon
On 20 Mar 2007 08:29:33 -0700, "are" wrote:
OK, spaceglobal.com says the propellant is MMH/NTO, same as for the attitude-control system. Isn't it a bit 20th-century to be using a relatively toxic propellants like that? The 21st century is not yet old enough, nor Elon Musk rich enough, to have completely reinvented all of rocketry from scratch. Unless you're planning on putting space on hold for the next twenty years, you are going to have to accept that rockets are going to go up with a whole lot of 20th-century stuff in them that the builders didn't feel they absolutely positively had to redesign. As the 20th century left us with a lot of very good, very reliable MMH/NTO thrusters and even cumbersome but proven techniques for handling MMH and NTO, there are going to be a lot of rocketeers who focus their limited R&D capability elsewhere and fly MMH/NTO. There will also be people who focus on green-propellant engines, but the rest of the industry isn't going to A: wait on them before going ahead with its own plans, or B: wager their plans against the green-propellant folks being ready when needed. -- *John Schilling * "Anything worth doing, * *Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" * *Chief Scientist & General Partner * -13th Rule of Acquisition * *White Elephant Research, LLC * "There is no substitute * * for success" * *661-718-0955 or 661-275-6795 * -58th Rule of Acquisition * |
#6
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SpaceX Dragon
In article .com,
are wrote: OK, spaceglobal.com says the propellant is MMH/NTO, same as for the attitude-control system. Isn't it a bit 20th-century to be using a relatively toxic propellants like that? It's six of one and half a dozen of the other. The trouble with MMH/NTO and its immediate relatives is toxicity, and the resulting handling hassles. But the good part is that proven, reliable hardware to use them is available off the shelf. Pick most anything else, and you may have solved the toxicity problem, but now you've got to develop a lot of the hardware from scratch. And that's not necessarily a simple exercise; the alternatives all have their own special problems, of one kind or another. So if you were trying to go after a bunch of NASA money -- like the COTS contract that SpaceX won -- it's not ridiculous to decide that at least the Mark 1 should use RCS/OMS hardware you can buy right now, even if it's costly and a hassle to use. It makes your proposal look less risky, and that may be more important than reducing operating costs later. -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
#7
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SpaceX Dragon
Yes, and the way to go after a bunch of NASA money is to increase recurring
costs. Plain and simple, and it works. Using Toxic fuel will probably drive them up, making development, testing, ground handling, safety more complex and increase turn around time. Clear the area while we do something with this toxic stuff. Ops, downtime, clean up that mess. Much higher recurring costs, and in the end, probably higher up front costs too. It also limits the multiple use of a heavy item, which SpaceX has been doing some of, with their innovative Falcon 1. Kerosine fuel and hydraulic fluid, Helium pressurization, roll control, attitude thrusters. You can't breath the stuff like other combinations (one that includes Oxygen). So, the choice just added a bunch of weight and complexity to another separate system. Handling it in space may also not be the best of ideas, leaks spewing toxic stuff, which limits another use operationally, offloading excess fuel and oxidizer at a space station/or space hotel. They might actually want any extra Oxygen and probably Hydrogen too, might actually be willing to pay for it. They may not be in the market for deltaV. So, he's limiting his future revenue streams, along with future business opportunities. As activities at a future Space Hotels, Space Stations, Space depots, Space industries complex, Space junkyards and Orbital transfer facility become a reality, the usefulness of cryogenic oxygen, hydrogen, nitrogen, methane, carbon dioxide (solid) will be obvious. They are simply commodities in a new Space Market Place. People will probably have to pay to recycle their excess MMH/NTO, rather than getting payed for their excess Oxygen, Hydrogen ... I agree, it's not ridiculous to decide to use the toxic stuff, but makes me wonder why it's not ridiculous. It's probably driven by NASA and some of their requirements in the contract. NASA is famous for writing contract requirements to get what they want, but not necessarily what they need. They simply need mass transportation and crew transportation to the Station, but should not be telling them how to do it in the requirements. The Tar Baby is holding a carrot, grab the carrot and the Tar Baby grabs you. That why my simplified model of where SpaceX is going has a -1 for such interactions. I also agree, it is a bit 20th-century thinking to use it in the 21st-century. But, NASA seems to be stuck in the 20th with their "Apollo on Steroids", the sequel, exploration plan. -- Craig Fink Courtesy E-Mail Welcome @ -- Henry Spencer wrote: In article .com, are wrote: OK, spaceglobal.com says the propellant is MMH/NTO, same as for the attitude-control system. Isn't it a bit 20th-century to be using a relatively toxic propellants like that? It's six of one and half a dozen of the other. The trouble with MMH/NTO and its immediate relatives is toxicity, and the resulting handling hassles. But the good part is that proven, reliable hardware to use them is available off the shelf. Pick most anything else, and you may have solved the toxicity problem, but now you've got to develop a lot of the hardware from scratch. And that's not necessarily a simple exercise; the alternatives all have their own special problems, of one kind or another. So if you were trying to go after a bunch of NASA money -- like the COTS contract that SpaceX won -- it's not ridiculous to decide that at least the Mark 1 should use RCS/OMS hardware you can buy right now, even if it's costly and a hassle to use. It makes your proposal look less risky, and that may be more important than reducing operating costs later. |
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