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SpaceX fully reusable launcher
I would love to hear opinions about Elon Musk's announcement a
fully reusable, two-stage launcher. In this SpaceX animated video -- http://www.youtube.com/watch?v=p176UpWQOs4 -- the launcher reminds me of the Falcon 9; it looks like the first stage has nine engines. I would think SpaceX would need a much more capable launcher, perhaps something more like the Falcon X or Falcon XX (sans its NERVA-based NTR, for political reasons) to get a decent payload and have enough fuel for a tail-first, soft landing. Would a LOX-kerosene first stage provide enough capability for such a launcher, or would SpaceX have to switch to a LOX-LH2 first stage? Musk made a comment about reusing such a launcher 1,000 times. Was he just stirring up interest, or could a tail-first, soft landing make it possible to reuse a launcher 1,000 times? |
#2
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SpaceX fully reusable launcher
At Sat, 1 Oct 2011 08:17:56 EDT byblow wrote:
I would love to hear opinions about Elon Musk's announcement a fully reusable, two-stage launcher. In this SpaceX animated video -- http://www.youtube.com/watch?v=p176UpWQOs4 -- the launcher reminds me of the Falcon 9; it looks like the first stage has nine engines. I would think SpaceX would need a much more capable launcher, perhaps something more like the Falcon X or Falcon XX (sans its NERVA-based NTR, for political reasons) to get a decent payload and have enough fuel for a tail-first, soft landing. Would a LOX-kerosene first stage provide enough capability for such a launcher, or would SpaceX have to switch to a LOX-LH2 first stage? You do know that the Saturn 5 first stage was LOX-kerosene, and it was able to send the Applo missions to the moon... Musk made a comment about reusing such a launcher 1,000 times. Was he just stirring up interest, or could a tail-first, soft landing make it possible to reuse a launcher 1,000 times? -- Robert Heller -- 978-544-6933 / Deepwoods Software -- http://www.deepsoft.com/ () ascii ribbon campaign -- against html e-mail /\ www.asciiribbon.org -- against proprietary attachments |
#3
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SpaceX fully reusable launcher
On 10/01/2011 09:13 PM, Robert Heller wrote:
At Sat, 1 Oct 2011 08:17:56 EDT wrote: I would love to hear opinions about Elon Musk's announcement a fully reusable, two-stage launcher. In this SpaceX animated video -- http://www.youtube.com/watch?v=p176UpWQOs4 -- the launcher reminds me of the Falcon 9; it looks like the first stage has nine engines. I would think SpaceX would need a much more capable launcher, perhaps something more like the Falcon X or Falcon XX (sans its NERVA-based NTR, for political reasons) to get a decent payload and have enough fuel for a tail-first, soft landing. Would a LOX-kerosene first stage provide enough capability for such a launcher, or would SpaceX have to switch to a LOX-LH2 first stage? You do know that the Saturn 5 first stage was LOX-kerosene, and it was able to send the Applo missions to the moon... The S-IC didn't attempt to fly back to the launch site, either. |
#4
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SpaceX fully reusable launcher
In sci.space.tech message 7cc88da8-a2c0-451f-b4a9-6528b15e6484@i9g2000y
qe.googlegroups.com, Sat, 1 Oct 2011 08:17:56, byblow posted: I would love to hear opinions about Elon Musk's announcement a fully reusable, two-stage launcher. In this SpaceX animated video -- http://www.youtube.com/watch?v=p176UpWQOs4 -- the launcher reminds me of the Falcon 9; it looks like the first stage has nine engines. I would think SpaceX would need a much more capable launcher, perhaps something more like the Falcon X or Falcon XX (sans its NERVA-based NTR, for political reasons) to get a decent payload and have enough fuel for a tail-first, soft landing. The current Falcon 9 will do about 10 tonnes to LEO, 5 tonnes to GTO, and the LEO price is of the order of $30M. Wikipedia figures. If they get just 10 flights per F9, but 1/2 the payload, the cost per go should be well under $10M (allowing for fuel, servicing, staff costs, etc.). That looks a price worth designing payloads for. Figures are pure guesses. BTW, the Video did not, as far as I recall, say that the second stage would flu back; the obvious route is once around Earth. And I think EM said that the video was not faithful to all planned detail. -- (c) John Stockton, nr London, UK. Turnpike v6.05 MIME. Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and 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. |
#5
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For my part, a few layman's observations and questions: First Stage: - Yes, it looks a lot like Falcon 9, byblow. SpaceX says they're all about economies of scale, so I guess it's no surprise this appears to be an evolutionary design. - It's nice how the landing gear fold into aerodynamic nacelles and tuck against the body for launch. - Is there an ablative surface on the front of the first stage? The video doesn't show this clearly. However, after separation the second stage appears to fire against the first stage as it departs. A clever way of conserving energy and saving fuel? - What happens to the black interstage element between separation and landing? Does it retract into the body somehow? Second stage: - Look at how the rocket nozzle both emerges from and contracts into the body, with the landing gear rocking in and out to provide clearance - very clever. - The ablative surface is asymmetrical, with more of it on one side. That means there's only one good orientation for re-entry, yes? - Will the ablative surface pose any difficulties for mating the payload atop it? - After the re-entry burn we don't see the main rocket firing again; as the stage touches down we only see small, side-rockets firing. Any thoughts as to what's going on here? Dragon: - Do we see anything which hasn't been shown in previous videos? It doesn't appear so, but perhaps I'm missing something. - What is the small surface, shown at the 'top' of Dragon, which folds down prior to ISS docking? Wow, so much going on here. Somebody please help me out: for SpaceX to pull this off, are they banking on using atmospheric oxygen for the propulsive landings? It seems doing so could save a great deal of weight, but... is such an approach readily possible? Do there exist rocket engines with the ability to switch from LOX to air-derived O2? Last edited by dglow : October 3rd 11 at 08:19 AM. |
#6
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SpaceX fully reusable launcher
On Oct 3, 6:41 am, dglow wrote:
snip Do there exist rocket engines with the ability to switch from LOX to air-derived O2? The proposed SABRE engines for the Skylon make the switch from air to LOX so I suppose they could do the opposite. Musk isn't a fan of space based solar power, but he does seem to be trying to get the lift cost down into the range where SBSP makes sense (100/kg to GEO). Some years ago I came to the conclusion that even LOX/LH2 isn't good enough and think it will take the exhaust velocity you can get from beamed energy to get the cost down. NASA does have a small project starting up that will investigate hydrogen skin heaters to around 10 MW/m^2. Keith Henson |
#7
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SpaceX fully reusable launcher
I'm curious about the first-stage landing technique. The video doesn't
show a a nose-first reentry for the first-stage, but as dglow astutely noticed, the front of the first-stage appears to have a heat shield that can handle the second-stage exhaust at separation. After separation, the first stage flips over and fires three of its nine engines to begin reentry (I wonder what altitude the stage will reach?). It's next shown descending tail first, possibly with just the center engine firing. The landing struts begin to deploy, rotating downward from a 12 o'clock position, to roughly 5 o'clock and 7 o'clock positions by touchdown. The landing struts appear rather wide, perhaps for extra drag during final descent. I wonder if they're thinking about using aerodynamic flaps as well? My guess is the first-stage does a nose-first reentry like the second- stage, flips over and goes into free fall during most of its descent through the atmosphere, perhaps using the RCS at the top of the stage to control its attitude. I'm curious about what altitude SpaceX envisions firing the center engine for final descent and landing. I assume only one engine is needed because most of its fuel is spent, and the second-stage and Dragon are absent. The Wiki article about the DC-X notes that if it could reach orbit, it would make an ideal craft for landing on the moon or Mars, the latter of which is Musk's ultimate goal. Perhaps he has visions of using the second stage as a Mars cargo lander to complement the Dragon-derived Mars people lander. He might need a fuel depot in earth orbit for such a scheme. Wiki: "Had a DC-type craft been developed that operated as an SSTO in Earth's gravity well, even if with only a minimum 4-6 crew capacity, variants of it might prove extremely capable for both Mars and Moon missions. Such a variant's basic operation would have to be "reversed"; from taking off and then landing, to landing first then taking off. Yet, if this could be accomplished on Earth, the weaker gravity found at both Mars and the Moon would make for dramatically greater payload capabilities, particularly at the latter destination." |
#8
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SpaceX fully reusable launcher
On Oct 3, 9:22 pm, byblow wrote:
My guess is the first-stage does a nose-first reentry like the second- stage, flips over and goes into free fall during most of its descent through the atmosphere, perhaps using the RCS at the top of the stage to control its attitude. I'm curious about what altitude SpaceX envisions firing the center engine for final descent and landing. I assume only one engine is needed because most of its fuel is spent, and the second-stage and Dragon are absent. I suspect that the key to this method is the reduction of reentry velocity, which would have to occur *before reentry*. The intent would be to reduce reentry heating, which has destroyed all of the Falcon stages launched to date, by reducing velocity at the "entry interface" (or whatever they call it). This requires the engines to fire well before reentry, probably even before apogee, which would mean starting them not long after staging. I'm just guessing though .... - Ed Kyle www.spacelaunchreport.com |
#9
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SpaceX fully reusable launcher
Would anyone care to venture a guess as to how much a fully reusable launcher -- based on a Falcon 9 -- could place in LEO? How about a fully reusable launcher with fully reusable side boosters? If cross-feed were used, would that result in the first-stage core booster going too high for the heat shield currently envisioned to protect it during descent? |
#10
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