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#11
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How much mass was saved by using a two-stage LM in Apollo?
"Jeff Findley" wrote:
True. In addition to the mass of the landing gear is the mass of the structure in the descent stage which was there to support and distribute the landing loads, which was a pretty big unknown before the first landing. No one really knew the physical properties of the lunar surface. That and no one knew how well the astronauts would do landing the LEM with the possibility of a lot of lunar dust being kicked up and obscuring the view. It was a real possibility that the landing could be pretty hard if the descent engine blew away enough dust to reveal a hard, rocky surface and the blowing dust made the view so bad the landing was hard to begin with. Sure, all those things were unknown before the first landing. But after the first landing NASA chose to not disrupt LEM production in order to update the design as the [LEM] program was already deeply in trouble. Thus Apollo 11 was, in some regards, obsolescent even before it flew. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#12
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How much mass was saved by using a two-stage LM in Apollo?
are writes:
The two stage version has the safety advantage that there's a back-up engine available should the descent engine fail during landing. In addition, the ascent engine can be very simple, and hence reliable, since it requires no throttle. The later flights damaged the decent engine bell on contact, didn't they? The seperate ascent engine was designed to be dirt-simple and discrete from the decent systems.. for good reasons... -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
#14
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How much mass was saved by using a two-stage LM in Apollo?
Derek Lyons wrote: Sure, all those things were unknown before the first landing. Not completely unknown, as he had the Surveyor landings to give us some indication of what the surface was like (the LM wasn't going to sink in the dread hundred-foot-deep layer of Moon dust, for instance). Surveyor 6 was particularly helpful in this regard as it lifted off from the lunar surface and then re-landed 2.5 meters away, letting the scientists get a look at the depressions created by the landing pads during the first landing. But after the first landing NASA chose to not disrupt LEM production in order to update the design as the [LEM] program was already deeply in trouble. Thus Apollo 11 was, in some regards, obsolescent even before it flew. It also had the landing probes extending from the bottom of the landing pads, to let the crew know when they were getting close to touchdown even if they were blinded by dust. as was mentioned in another thread a few months ago, the dust thrown up by the landing engine shot out at very high velocity, and in the vacuum of the Moon kept right on going at that velocity until gravity pulled it back to the surface, sandblasting one side of the Surveyor 3 spacecraft during the landing of Apollo 12's LM, despite the distance of the LM from the Surveyor: http://upload.wikimedia.org/wikipedi...000-001316.jpg During Apollo this wasn't a problem, but it will be a problem if we ever build a permanent Moonbase and need to resupply it via cargo landers. Every time one lands the Moonbase is going to get hit by something like a horizontal micrometeor shower. And you don't want to be standing outside when it hits, as it's not going to help the clarity of your helmet's faceplate one iota. Pat |
#15
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How much mass was saved by using a two-stage LM in Apollo?
Pat Flannery wrote:
Derek Lyons wrote: Sure, all those things were unknown before the first landing. Not completely unknown, as he had the Surveyor landings to give us some indication of what the surface was like But after the first landing NASA chose to not disrupt LEM production in order to update the design as the [LEM] program was already deeply in trouble. Thus Apollo 11 was, in some regards, obsolescent even before it flew. I thought it would be clear that Jeff was calling A11 the first landing, while I was subtly reminding him it was not. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#16
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How much mass was saved by using a two-stage LM in Apollo?
On Mar 24, 5:32 am, "Alan Erskine" wrote:
"Matt" wrote in message ... On Mar 24, 6:03 am, "Alan Erskine" wrote: Couldn't be too much - extra engine; propellant and pressurant tanks; extra insulation on the underside of the Ascent Stage etc, as well as the separation mechanism and other systems. I thought it was more about reducing the mass the ascent stage engine had to lift back off the Moon. Yeah, but if you had an empty 'Descent stage' (minus all the bits-and-pieces I mentioned above), it wouldn't be _that_ much heavier. I might have to do some heavy-duty research to find out - check out system weights etc and deduct them from the DS structure. Remember, it would also mean the descent stage would be lighter and therefore use less propellant during descent; making more propellant available for the combined ascent. It didn't quite work anyway you'd care to cut it, so what's the difference? .. - Brad Guth |
#17
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How much mass was saved by using a two-stage LM in Apollo?
On Mar 24, 7:52 am, "Alan Erskine" wrote:
"Greg D. Moore (Strider)" wrote in ... Consider you need tanks and engine. The mass of the tank compared to the mass of the fuel probably isn't that much. The DS tanks could have been extended - not by much either - they were considerably greater diameter than the AS tanks. Also, the AS tanks were spherical - basically, two domes welded together; so a small (cylindrical) extension in the length of the DS tanks would have been much lighter than that. Sure, as a % of propellant capacity, the saving might not have been that great, but if all the systems _exclusive_ to the AS that were essentially duplicates of the DS systems; the difference might be substantial. So extra tankage probably doesn't hurt as much there as one might think. And then there's all the insulation panels under the AS. Think of the increase in useable volume inside the AS. And there's all the panelling on top of the DS - designed to prevent the thrust of the ASE from penetrating into the DS. Wouldn't need that either. The mass of the engine I'm guessing is a more significant issue. According to EA (http://www.astronautix.com/engines/tr201.htm), the AS Engine weighed 113kg. Plus all the pressurising tanks; plumbing (and the pyrotechnics that go with stage sep) Does anyone know how much the landing gear weighed? hmmmm.... I'm sure there's not going to be that much of a difference in total mass - and then there's the residual prop in the DS - AS11 had 20 seconds, but the other landings had over 60 seconds each - that adds up to quite a bit of mass too. You're trying to fix something that according to the lord almighty (aka NASA/Apollo) was absolutely perfect in every possible way, that oddly can't be replicated as of today or of any other time in order to save their own soul. .. - Brad Guth |
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