Quote from: cambrianera on 12/05/2015 04:44 pmIt has amazing cryo properties.As to flammability, do you realize that SpaceX is already embedding carbon fiber inside LOX tank?Lot of mitigation factors can be considered.Where?
It has amazing cryo properties.As to flammability, do you realize that SpaceX is already embedding carbon fiber inside LOX tank?Lot of mitigation factors can be considered.
Quote from: Earendil on 12/05/2015 07:18 amSO why was he allowed to attempt a landing and SX is not?You're comparing apples and oranges. SpaceX already had similar permission for their Grasshopper testbed program in Texas and was planning to do higher altitude hops similar to Blue's at Spaceport America, but their plans changed.RTLS at a Government launch site is an entirely different situation, where the booster is flying back from hundreds of miles downrange with a huge radius of potential impact points if its guidance system were to go astray. New Shepard and Grasshopper were going straight up with limited propellants and thus limited ability to stray from their privately-owned test sites. And in Blue's case it helps if you own 290,000 acres of empty scrubland. There's not much out there to hit if things go wrong. Contrast that with Cape Canaveral/KSC/Cocoa Beach, where there are plenty of buildings and people relatively near the landing site. The risk equation is much different.
SO why was he allowed to attempt a landing and SX is not?
So far - one guy tweeted with unnamed sources. Not very compelling. Yet.
Here is an overview I created of the KSC / CCAFS assets in a satellite view. Grey markers are inactive/demolished. Blue markers are active, or at least leased. Most information came from Wikipedia. Feel free to PM me with suggested corrections, additions, links that should be included in details, etc. Especially for the few buildings scattered between the Air Force Station and the pads. I think one of them is an armory, so that could be important. I ran out of attention, but plan to add more pads and assets.http://tiny.cc/ksc-ccafs-assets-mapNOTE: The one mile polygon around LC-13 was just to help me with some sense of scale, it is in no way an official criteria for anything (accuracy, blast, etc.)
One last thing wrt land landing with this RTF. The last attempt was primarily foiled by a stuck valve causing the stage to overshoot, it tried to compensate...etc, boom. It's fair to say they have mitigated that potential issue as they have with Hydraulics, etc. But that valve response was off by all of 2 seconds or less. Landing this stage is an epic battle of precision. A battle they have not yet won. A battle, if I was the Range, would prefer to keep at sea until it was.
Landing this stage is an epic battle of precision. A battle they have not yet won.
Quote from: rcoppola on 12/05/2015 06:38 pmLanding this stage is an epic battle of precision. A battle they have not yet won.Well, they haven't won it at sea yet. But they have demonstrated it on land numerous times with test vehicles.I see a lot of analogies for what they are doing as when a pilot lands an aircraft. Ideally when landing an airplane you want to have a stabilized flight path when landing, where only small corrections need to be made. If you have a big landing area you're shooting for (i.e. a Cessna 172 landing on a runway built for large jets) you don't have critical corrections you have to make. But if you're an F-18 pilot coming in on an aircraft carrier at night in stormy weather, then if you need to nail that first landing you are making continuous fine & large adjustments all the way down.To me landing on the barge is like landing on the aircraft carrier, and landing on land is like landing at the large commercial airport.I don't have too much concern about the land landing, assuming they have the fuel to get back.
Regarding the struts, the two mitigation steps I saw discussed were increasing the strength of the strut and possibly doing 100% testing. However the strut already had a more than adequate 5:1 load factor. The failure occurred because of poor control of the manufacturing process, not a design flaw. An unanticipated falure mode in the design would have been present in every strut and would in almost all cases have failed within the first few flights. Inconsistent manufacturing is best detected by selecting periodic samples and testing to ultimate strength. This cannot be done with 100% of the parts, nor is this necessary.As C. Edwards Deming pointed out years ago, if manufacturing process is under adequate control a quantitative parameter such as strength at failure in a sample of parts consistently falls into a normal distribution with a standard deviation that is only a fraction of the specified variability. If even a few measurements fall outside of the normal distribution then the process is not under control. Testing doesn't correct the problem. The corrective action is to identify the source of the variability in quality and correct the manufacturing process. Of course NDT of various types can be done with 100% of output, but this doesn't provide a quantitative measure of the critical property, in this case strength.
Regarding the struts, the two mitigation steps I saw discussed were increasing the strength of the strut and possibly doing 100% testing. However the strut already had a more than adequate 5:1 load factor. The failure occurred because of poor control of the manufacturing process, not a design flaw.
Inconsistent manufacturing is best detected by selecting periodic samples and testing to ultimate strength. This cannot be done with 100% of the parts, nor is this necessary.As C. Edwards Deming pointed out years ago...
Testing doesn't correct the problem. The corrective action is to identify the source of the variability in quality and correct the manufacturing process.