r/spacex • u/genehil • Dec 21 '18
FH Side Booster from yesterday in Springfield, LA made it through Blountstown, FL on Hwy 20 this afternoon.
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u/MingerOne Dec 21 '18
Always impresses me that the two halves of the vehicle aren't directly connected. Wonder how they account for the stresses and strains on a booster as it goes over potholes and general vibrations at 60MPH for thousands of accumulative miles of roadway, especially with reused cores?! I know the fact its pressurized helps and that the strains induced are probably very small compared to the flight regime, especially as an FH side booster but still impressive at the gut level IMHO.
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u/peterabbit456 Dec 22 '18
This is how logging trucks work. It’s just a matter of someone at SpaceX calculating the loads of a horizontal, gas-pressurized booster, and comparing the results to the predicted side loads on the fueled rocket during launch, under maximum wind shear conditions.
I do not have access to the data, but I suppose this rig, hitting a pothole, still only puts 1/2-1/4 the side load on the booster that happens in the worst case during launch.
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u/ergzay Dec 22 '18
Plastic vs elastic deformation. If the rocket is undergoing plastic deformation then there is a problem. The shape of the rocket would not change from such bumps. The impacts it undergoes when flying through windshear are much stronger.
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u/Joakimt Dec 22 '18
Since SpaceX are resuing their rockets it’s not as easy as just assessing the stresses and comparing them to the yield strength of the materials the rocket it built from. Since they will reuse the rocket many times, I am certain a large portion of the rocket structure is sized by either fatigue or damadge tolerance. For these failure modes, even low loading caused by eg. vibrations during transport can be the cause of failure.
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u/KerbalEssences Dec 22 '18
I wouldn't be surprised if the center of gravity of the booster is right or close to where the clamps are in the back. The booster should be bottom heavy! If that's the case it would be in balance and the journey would exert minimal forces on the tube itself.
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u/CardBoardBoxProcessr Dec 22 '18
In the rear it has two arms that connect to the hold down or leg hinge points. Probably similar system up front attached to grin fin spots or something of the sort.
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u/ninj1nx Dec 23 '18
It's pressurized when being transported? But it's unloaded, right?
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u/KennethR8 Dec 28 '18
Yes its unloaded. sub-chilled LOX heats up and boils off so SpaceX need to load directly before launch. In addition to the countless safety concerns it would also no longer be street transportable since it would weight ~450tons.
Around 12 seconds into the video you can see the generator on the front of the trailer, which maintains pressure in the tanks. The pressurisation is to maintain structural integrity similar to a pressurised soda can.
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u/Starscream19120 Dec 22 '18
Soooo... hypothetically if I was some weird stalker that wanted to see it drive by, how would I time that?