Quote from: mgfitter on 10/24/2016 07:50 pmAssuming they can make these tanks work, what is the likely mass advantage of a liner-less composite tank vs. a traditional Aluminum alloy tank of similar capacity?Are we talking about a 10%, 30%, 50% reduction in mass?-MGAs Elon said."At worst we will have to line the tanks with either a spray on sealant or invar." (not exact quote)This doesn't sound as bad of a mass penalty of going with an all Al tank.
Assuming they can make these tanks work, what is the likely mass advantage of a liner-less composite tank vs. a traditional Aluminum alloy tank of similar capacity?Are we talking about a 10%, 30%, 50% reduction in mass?-MG
Quote from: HMXHMX on 10/24/2016 08:58 pmQuote from: mgfitter on 10/24/2016 07:50 pmAssuming they can make these tanks work, what is the likely mass advantage of a liner-less composite tank vs. a traditional Aluminum alloy tank of similar capacity?Are we talking about a 10%, 30%, 50% reduction in mass?-MGIt depends on a number of factors, but when I have designed medium-volume launch vehicle tanks (EELV class) the aluminum ones tends to be about 0.7-0.8 lbm/pcf (all you smart folks can no doubt convert to your units of preference) while pure composite are in the range of 0.4-0.5.well I can guess that lbm is pounds mass.pcf is percent fuel?Edit: acronym finder says per cubic foot(off)
Quote from: mgfitter on 10/24/2016 07:50 pmAssuming they can make these tanks work, what is the likely mass advantage of a liner-less composite tank vs. a traditional Aluminum alloy tank of similar capacity?Are we talking about a 10%, 30%, 50% reduction in mass?-MGIt depends on a number of factors, but when I have designed medium-volume launch vehicle tanks (EELV class) the aluminum ones tends to be about 0.7-0.8 lbm/pcf (all you smart folks can no doubt convert to your units of preference) while pure composite are in the range of 0.4-0.5.
Quote from: brickmack on 10/24/2016 03:00 pmQuote from: docmordrid on 10/24/2016 08:15 amI would think a plain flat barge without expensive hardware aboard. That way stage landings aren't compromised if it flunks out.What would the failure modes be here? If the tank fails I wouldn't expect a huge amount of damage to the barge, theres not much fuel to combust with. And they've dealt with barge explosions before anywayAgain ambiguity in Elon's answer, didn't specify what the tank is filled with during the pressure test. Could be just freshwater. Then the biggest danger to the barge is to get wet on the topside too.
Quote from: docmordrid on 10/24/2016 08:15 amI would think a plain flat barge without expensive hardware aboard. That way stage landings aren't compromised if it flunks out.What would the failure modes be here? If the tank fails I wouldn't expect a huge amount of damage to the barge, theres not much fuel to combust with. And they've dealt with barge explosions before anyway
I would think a plain flat barge without expensive hardware aboard. That way stage landings aren't compromised if it flunks out.
Or, you do what Musk said - use an Invar liner which is tough and minimizes expansion/contraction issues.
Quote from: uhuznaa on 10/24/2016 03:13 pmBy the way, Musk confirmed (Reddit AMA) that the smaller spherical tanks in the main tanks contain the landing propellants:"Those are the header tanks that contain the landing propellant. They are separate in order to have greater insulation and minimize boil-off, avoid sloshing on entry and not have to press up the whole main tank.""The liquid oxygen transfer tube serves as the header tank for ox"I get the award
By the way, Musk confirmed (Reddit AMA) that the smaller spherical tanks in the main tanks contain the landing propellants:"Those are the header tanks that contain the landing propellant. They are separate in order to have greater insulation and minimize boil-off, avoid sloshing on entry and not have to press up the whole main tank.""The liquid oxygen transfer tube serves as the header tank for ox"
Quote from: Burninate on 10/12/2016 01:37 pmSubcooling of the methane is assumed. Subcooling of the LOX is not something you're going to get; Too much weight.Your sentence makes little sense. Part of Methane's attraction is it can be operated at very close to the same (sub cooled) temperature as LOX, keeping the thermal gradient across any common bulkhead tanks quite low. If you can do one, you can do the other.
Subcooling of the methane is assumed. Subcooling of the LOX is not something you're going to get; Too much weight.