Watching Falcon Heavy's side boosters land, I was amazed that they could withstand the stresses of re-entry yet still fire again for a (relatively) slow, smooth landing.

I see there are heat shields on the bottoms of those boosters, but what is special about the Merlin engines themselves to enable them all the stress of liftoff, re-entry, and another ignition for landing? How do the parts at the bottom of the booster withstand re-entry yet still function?

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    $\begingroup$ It is not like a reentry from a low orbit. The boosters will separate at lower height and speed. $\endgroup$ – Uwe Feb 6 '18 at 21:07

Remember on the way up those engine bells are taking an amazing amount of heat from burning LOX and RP1. They can handle a LOT of heat.

On the way down, they take most of the heat on the engine bells, designed to take it, and then the components above it, are the ones with protection.

SpaceX has been iterating and evolving the materials and equipment to better survive with each launch. The final iteration is expected to be the Block 5 Falcon 9 version that should be very reusable for at least 10 flights. It is expected by the mid point of 2018 to fly a mission.

Prior to this launch, SpaceX has landed 21 boosters successfully. Several have made it all the way down, but for variety of reasons did not end up standing. (Like the GovSat-1/SES-16 booster the previous week. It landed on the water, since the OCISLY ASDS was required for this mission, and was found lying on its side in the water. Does not count as a successful landing, but sort of was.).

In fact both the side boosters are on their second flights. Thaicomm-8 and CRS-9 missions were the previous flights of these boosters.

  • $\begingroup$ The side boosters from the flight today are re-used ones? Amazing! $\endgroup$ – cr0 Feb 6 '18 at 21:23
  • $\begingroup$ New boosters cost money man! You want affordable space flight? You got reduce, reuse, recycle! $\endgroup$ – geoffc Feb 6 '18 at 21:30
  • $\begingroup$ As a geoscientist I'm right there with ya on the need. As a novice to rocket science, I'm in awe. $\endgroup$ – cr0 Feb 6 '18 at 21:41
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    $\begingroup$ @cr0 This F-H is actually not representative of what they plan to fly. Proper F-H will use Block 5 cores for side and core. But this was cheap and easy to get most of the testing needed. Besides Block 5 will likely fly a lot before the next F-H so they will know the core works. $\endgroup$ – geoffc Feb 6 '18 at 22:06
  • $\begingroup$ I know that in KSP, one often reenters vehicles using the engine as a heat shield. I had no idea this worked in real life. $\endgroup$ – ikrase Feb 19 at 5:21

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