KSK Posted January 15, 2018 Share Posted January 15, 2018 (edited) Serious question - does anyone know how COPV helium bottles compare structurally to the composite propellant tanks planned for BFR? I'm wondering if that might be something of a silver lining on the ASAP cloud? As well to get these concerns out of the way now before bringing BFR into production. Edited January 15, 2018 by KSK Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 7 minutes ago, KSK said: Serious question - does anyone know how COPV helium bottles compare structurally to the composite propellant tanks planned for BFR? I'm wondering if that might be something of a silver lining on the ASAP cloud? As well to get these concerns out of the way now before bringing BFR into production. They are very different. COPVs are Composite-Overwrapped Pressure Vessels; they are aluminum tanks wrapped in carbon-fiber composite. The aluminum encloses/seals the vessel contents while the composite provides high tensile strength with lower structural mass than a pure-aluminum solution. The BFR is intended to dispense with the aluminum liner altogether. This is a big challenge; pure oxygen likes to eat everything, but especially carbon. I am not sure exactly how they plan to preserve interior surface integrity with multiple cycles of hot and cold oxygen loading, especially considering that they plan on using autogenous pressurization. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted January 15, 2018 Share Posted January 15, 2018 4 minutes ago, sevenperforce said: They are very different. COPVs are Composite-Overwrapped Pressure Vessels; they are aluminum tanks wrapped in carbon-fiber composite. The aluminum encloses/seals the vessel contents while the composite provides high tensile strength with lower structural mass than a pure-aluminum solution. The BFR is intended to dispense with the aluminum liner altogether. This is a big challenge; pure oxygen likes to eat everything, but especially carbon. I am not sure exactly how they plan to preserve interior surface integrity with multiple cycles of hot and cold oxygen loading, especially considering that they plan on using autogenous pressurization. Think BFR goes away from using helium at all at least for the upper stage. Instead they use pressurized metan and oxygen. Kind of like ULA is moving on the centaur replacement. For one you can not refuel helium on Mars, just orbital refueling would be hard. And oxygen in composite tanks are fun in an very Kerbal way. They will need some sort of liner. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 3 minutes ago, magnemoe said: Think BFR goes away from using helium at all at least for the upper stage. Instead they use pressurized metan and oxygen. Kind of like ULA is moving on the centaur replacement. For one you can not refuel helium on Mars, just orbital refueling would be hard. And oxygen in composite tanks are fun in an very Kerbal way. They will need some sort of liner. Right, that's the other difference: the COPVs are for holding helium at ridiculously high pressure; the BFR tanks are holding cryo methane and LOX at considerably lower pressures. IIRC Musk said they were going to linerless on the LOX tanks but who knows how reliable that is. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 15, 2018 Share Posted January 15, 2018 51 minutes ago, sevenperforce said: Ditto this. I have been out of likes all morning. Double double dittos. Also, @KSK et al, IIRC one of the items planned for Block 5 are new helium tanks... Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 3 minutes ago, CatastrophicFailure said: Also, @KSK et al, IIRC one of the items planned for Block 5 are new helium tanks... They determined that the AMOS-6 failure could be prevented in the future either by a slower fuel loading process or a COPV redesign, so they've been doing less efficient fuel loading on the Block 3s and Block 4s that are flying right now, and the Block 5s will return to the more efficient fuel loading with new COPVs. Quote Link to comment Share on other sites More sharing options...
KSK Posted January 15, 2018 Share Posted January 15, 2018 Thanks everyone! It sounds like the ASAP report has effectively already been actioned then, at least with regard to the COPVs. That's good. Have to admit that I'm curious as to the technicalities of storing LOX or even GOX in a carbon tank but I think it's safe to assume that the SpaceX engineers have spotted the 'elephant in the room' problem there. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 8 minutes ago, KSK said: Have to admit that I'm curious as to the technicalities of storing LOX or even GOX in a carbon tank but I think it's safe to assume that the SpaceX engineers have spotted the 'elephant in the room' problem there. Well, we all know what happens when you put LOX in a carbon tank: Just kidding, this was a burst test, not a failure. BFR components are already flying! In all seriousness, there's like 7 pages of discussion over here: https://forum.nasaspaceflight.com/index.php?topic=41378.40 NASA has had success with ionic epoxy composites with GOX and LOX at various pressures. Quote Link to comment Share on other sites More sharing options...
PB666 Posted January 15, 2018 Share Posted January 15, 2018 (edited) 1 hour ago, sevenperforce said: The BFR is intended to dispense with the aluminum liner altogether. This is a big challenge; pure oxygen likes to eat everything, but especially carbon. I am not sure exactly how they plan to preserve interior surface integrity with multiple cycles of hot and cold oxygen loading, especially considering that they plan on using autogenous pressurization. LOX does not neccesarily autocombust carbon. Remember that diesel explodes in the presence of compressed air at STP. but that is not true for unsubstituted aeromatics, the have 4n+2 stabilization, thats why octane (and at one time, tetra-ethyl lead) to improve performance in gasoline, too much benzene. The more of these connected in the ground structure, the more stable they are and the less energy they generate on combustion. Its the reason coal burns so slowly and produces so much energy relative to other fuels. There are things that you can do to the surface of carbon fiber in excess of what is innate to prevent the explosion danger. The critical ingredient is that you need something with the same thermal expansion rate as the carbon fiber (or a little less since it is inside the tank), that is inert to oxygen. Certain forms of silicon (like the silicon you use on the screen of your iPhones) that a very thin and very durable. And alternative is to have a slightly different carbon fiber layer on the inside and the outside. The question I might ask, if you could make it safe . . . .why wouldn't you use a carbon fiber tank on a reusable launch vehicle? Thats probably another 5 to 10 kT of PL to orbit right there. (you need less fuel to retro back to the pad, thats for certain the tanks are a significant part of the empty mass). This mean more dV to craft and a greater velocity tolerance to return to launch pad. The concept of space travel in its very nature is such that the process you are involved in produce huge sums of specific energy that in any other context would be as dangerous as hell. There is no reason to say we'll take a risk this direction, but not that direction. You have to parallel those risk and individually mitigate them. The safety issue you ignore will be the one that gets you. Why do they spray water at the launch ejecta, or sparkle under the engines, or use launch clamps. All of these things are varied system stabilizations. The other thing is that some of you guys think the Orion interplanetary drive system could be a thing . . . . that's a huge risk, so many risks would have to be mitigated to make that work. If you are worried about carbon fiber tanks constituitively autocombusting, best to keep the feet on the ground. 22 minutes ago, sevenperforce said: Well, we all know what happens when you put LOX in a carbon tank: Just kidding, this was a burst test, not a failure. BFR components are already flying! In all seriousness, there's like 7 pages of discussion over here: https://forum.nasaspaceflight.com/index.php?topic=41378.40 NASA has had success with ionic epoxy composites with GOX and LOX at various pressures. The question is how much pressure. Edited January 15, 2018 by PB666 Quote Link to comment Share on other sites More sharing options...
tater Posted January 16, 2018 Share Posted January 16, 2018 It’s also important to realize that commercial crew is not anything like commercial cargo. NASA is micromanaging it, often causing delays measured in years. The bar for the 2 new crew vehicles is higher than for Orion, and it has changed, always in a way that delays. I think some is to not entirely obviate Orion. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted January 16, 2018 Share Posted January 16, 2018 10 hours ago, tater said: It’s also important to realize that commercial crew is not anything like commercial cargo. NASA is micromanaging it, often causing delays measured in years. NASA haven't yet started managing spaceships with several tens of civilians flying to Mars. So, I believe in humanity first time arriving to Mars in brand new and shining spaceships, built by the United Spoiler Alliance of Nuclear Plant Manufacturers of Australia and New Zealand, launched from the National Nuclear Center in Victoria Desert. At least not sooner. Quote Link to comment Share on other sites More sharing options...
NSEP Posted January 16, 2018 Share Posted January 16, 2018 No delays for FH static fire today in about 7 hours? Seems good! Quote Link to comment Share on other sites More sharing options...
StarStreak2109 Posted January 16, 2018 Share Posted January 16, 2018 Hopefully the day of days has come! Holding my breath! Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted January 16, 2018 Share Posted January 16, 2018 In other news, the total flight time for Dragon has now reached a whopping 367 days, 23 hours with the return of CRS-13 - which means Dragon now has more than a year of total flight time. Not bad at all for a spacecraft that started flying only 7 years ago. Quote Link to comment Share on other sites More sharing options...
Scotius Posted January 16, 2018 Share Posted January 16, 2018 Not bad for a company that was founded in 2002. In fifteen years they went from nothing to a very capable, reuseable launch system, reuseable cargo craft and a very strong position in the space launch market. Deep i my heart, i hope that at the end of the next fifteen years period we'll see a man leaving a footprint on Mars surface. Quote Link to comment Share on other sites More sharing options...
NSEP Posted January 16, 2018 Share Posted January 16, 2018 The Falcon Heavy static fire in 3 hours? No delays? Still? I hope they don't push it back on the last moment. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 16, 2018 Share Posted January 16, 2018 According to SpaceFlightNow, there’s been no confirmation of anything today. I’d say it’s still pretty up in the air. Er, metaphorically, That is. Quote Link to comment Share on other sites More sharing options...
NSEP Posted January 16, 2018 Share Posted January 16, 2018 At what t- do live streams pop up on Youtube before static fires? Crossing my fingers now... Quote Link to comment Share on other sites More sharing options...
tater Posted January 16, 2018 Share Posted January 16, 2018 No static fire today, apparently. Boo. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted January 16, 2018 Share Posted January 16, 2018 (edited) Here’s hoping they get to light that triple candle today. The window is supposed to open at 4pm EST, half an hour before I get off work. So hopefully when I’m off work and check my phone, this thread will be a few pages longer Bah humbug Edited January 16, 2018 by StrandedonEarth Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 16, 2018 Share Posted January 16, 2018 1 minute ago, tater said: No static fire today, apparently. Boo. [frustrated conniptions] Quote Link to comment Share on other sites More sharing options...
NSEP Posted January 16, 2018 Share Posted January 16, 2018 Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted January 16, 2018 Share Posted January 16, 2018 I'm going to put out a prediction - Falcon Heavy will launch on Valentine's Day. I hope I'm wrong (in one direction, not the other). There's always tomorrow, though! We've waited six years, we can wait another few weeks for the launch. Quote Link to comment Share on other sites More sharing options...
Shpaget Posted January 16, 2018 Share Posted January 16, 2018 (edited) 6 minutes ago, Ultimate Steve said: we can wait another few weeks for the launch. Speak for yourself! I've been pestering my colleagues at work for a week now with some rocket stuff thing. Edited January 16, 2018 by Shpaget Quote Link to comment Share on other sites More sharing options...
cubinator Posted January 16, 2018 Share Posted January 16, 2018 1 hour ago, Shpaget said: Speak for yourself! I've been pestering my colleagues at work for a week now with some rocket stuff thing. Me too! What if by the time it launches Mars is in the right place for a direct transfer? Quote Link to comment Share on other sites More sharing options...
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