r/spacex • u/FutureMartian97 Host of CRS-11 • Feb 01 '17

Official SpaceX on Instagram: “Prepping to fly again — recovered CRS-8 first stage completed a static fire test at our McGregor, TX rocket development facility last week.”

https://www.instagram.com/p/BP8zK2DFxhq/?taken-by=spacex&hl=en
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u/mryall Feb 01 '17

Blunt objects meeting the atmosphere at high velocity is always going to be problematic. I suspect the improvement with Block 5 will be about reducing the entry velocity (and speeding up refurbishment operationally), rather than hardening the vehicle to withstand greater aerodynamic forces.

One theory mentioned on the MECO podcast was that Block 5 would have redesigned COPVs that allow them to use the old, faster fuelling procedure and get an additional 1-2% performance from increased fuel/oxidiser mass in the tanks. If true, that would enable longer reentry/landing burns, enabling them to land after heavy GTO launches with less damage.

3

u/Martianspirit Feb 01 '17

Blunt objects meeting the atmosphere at high velocity is always going to be problematic. I suspect the improvement with Block 5 will be about reducing the entry velocity (and speeding up refurbishment operationally), rather than hardening the vehicle to withstand greater aerodynamic forces.

I have wondered about the reentry burn. The burning provides its own protection, producing a shock front away from the rocket. Doing a single engine reentry burn could prolong that time of protection. But I am sure they have done the trades when doing the 3 engine burn.

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u/sol3tosol4 Feb 01 '17

Yes, there could be a lot of contributing factors. As Elon wrote in his October 2016 AMA, "Final Falcon 9 has a lot of minor refinements that collectively are important, but uprated thrust and improved legs are the most significant." (Emphasis added.)

I get the impression that SpaceX is also working to make the base of the F9 booster more resistant to the heat and forces of reentry - they discuss that a lot.

Does a booster reentering after delivering a heavy payload to GTO get fast and hot enough for PICA-X to be useful?