This helps to maintain the propellant temperature in the required range and also keeps the outside of the tank from getting too cold, which would condense and freeze the water vapor in the air into ice; ice is a debris hazard and would add additional weight to the vehicle, reducing overall performance. During the early stages of ascent, the foam also provides thermal protection from aerodynamic heating.
I'm curious: Why does the SLS need foam insulation, while other launchers (such as SpaceX Falcon 9) manage without any such foam insulation?The article says:QuoteThis helps to maintain the propellant temperature in the required range and also keeps the outside of the tank from getting too cold, which would condense and freeze the water vapor in the air into ice; ice is a debris hazard and would add additional weight to the vehicle, reducing overall performance. During the early stages of ascent, the foam also provides thermal protection from aerodynamic heating.I would have thought the foam would impose a greater weight penalty than any condensed ice.
Quote from: cmcqueen on 12/11/2017 12:20 amI'm curious: Why does the SLS need foam insulation, while other launchers (such as SpaceX Falcon 9) manage without any such foam insulation?The article says:QuoteThis helps to maintain the propellant temperature in the required range and also keeps the outside of the tank from getting too cold, which would condense and freeze the water vapor in the air into ice; ice is a debris hazard and would add additional weight to the vehicle, reducing overall performance. During the early stages of ascent, the foam also provides thermal protection from aerodynamic heating.I would have thought the foam would impose a greater weight penalty than any condensed ice.The SLS uses liquid hydrogen (LH2) fuel and the liquid oxygen (LOX) oxidizer which would boil off without insulation.
Quote from: Rocket Science on 12/11/2017 12:25 amQuote from: cmcqueen on 12/11/2017 12:20 amI'm curious: Why does the SLS need foam insulation, while other launchers (such as SpaceX Falcon 9) manage without any such foam insulation?The article says:QuoteThis helps to maintain the propellant temperature in the required range and also keeps the outside of the tank from getting too cold, which would condense and freeze the water vapor in the air into ice; ice is a debris hazard and would add additional weight to the vehicle, reducing overall performance. During the early stages of ascent, the foam also provides thermal protection from aerodynamic heating.I would have thought the foam would impose a greater weight penalty than any condensed ice.The SLS uses liquid hydrogen (LH2) fuel and the liquid oxygen (LOX) oxidizer which would boil off without insulation.Your point about liquid hydrogen is true, but not liquid oxygen. Many (most) other launch vehicles use LOX without jumping through all these hoops for insulating foam.
I'm curious: Why does the SLS need foam insulation, while other launchers (such as SpaceX Falcon 9) manage without any such foam insulation?
Applying foam to the interstage and the forward skirt seems a bit much. Any particular reason why it's being done with SLS?
Applying foam to the intertank and the forward skirt seems a bit much. Any particular reason why it's being done with SLS?
Quote from: Oli on 12/11/2017 09:33 pmApplying foam to the intertank and the forward skirt seems a bit much. Any particular reason why it's being done with SLS?For the same reason most of SLS decisions are justified... Because that's how it was done with Shuttle.No matter what anyone will tell you, this kind of foam is not necessary for LH2, and has many problems. You only need to look back at Saturn V - which flew with two LH2 stages with far longer loiter times - to see that is not necessary.
Although several S-II stages were produced with the original insulation concept, the results were so discouraging that North American spent considerable time and money working up an alternative. Instead of making up panels and affixing them to the tank, the company finally evolved a process for spraying insulation material directly onto the tank walls (eliminating the air pockets), letting it cure, then cutting it to the proper contour. This technique turned out to be much more economical and much lighter than the insulation panels.
Quote from: Lars-J on 12/12/2017 03:23 amQuote from: Oli on 12/11/2017 09:33 pmApplying foam to the intertank and the forward skirt seems a bit much. Any particular reason why it's being done with SLS?For the same reason most of SLS decisions are justified... Because that's how it was done with Shuttle.No matter what anyone will tell you, this kind of foam is not necessary for LH2, and has many problems. You only need to look back at Saturn V - which flew with two LH2 stages with far longer loiter times - to see that is not necessary. In case you had failed to notice: both LH2 tanks on Saturn V (the one on S-II and the one on S-IVB) were insulated. Boil-off was the prime reason.S-IVB LH2 tank was insulated on the inside. S-II LH2 tank was insulated on the outside.Read from here: https://history.nasa.gov/afj/s-ii/s-ii-insulation.htmlYou will also discover where spray-on-foam originated from: S-II
Quote from: woods170 on 12/12/2017 09:34 amQuote from: Lars-J on 12/12/2017 03:23 amQuote from: Oli on 12/11/2017 09:33 pmApplying foam to the intertank and the forward skirt seems a bit much. Any particular reason why it's being done with SLS?For the same reason most of SLS decisions are justified... Because that's how it was done with Shuttle.No matter what anyone will tell you, this kind of foam is not necessary for LH2, and has many problems. You only need to look back at Saturn V - which flew with two LH2 stages with far longer loiter times - to see that is not necessary. In case you had failed to notice: both LH2 tanks on Saturn V (the one on S-II and the one on S-IVB) were insulated. Boil-off was the prime reason.S-IVB LH2 tank was insulated on the inside. S-II LH2 tank was insulated on the outside.Read from here: https://history.nasa.gov/afj/s-ii/s-ii-insulation.htmlYou will also discover where spray-on-foam originated from: S-IIOf course insulation is needed, did I say otherwise? Read again... "this kind of foam". As in what it is and its application method.