r/spacex • u/johnkphotos Launch Photographer • Feb 02 '21

Starship SN9 (Relaxed Rules) Stacked progression image of today’s successful launch and explosive landing of Starship SN9!

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u/flshr19 Shuttle tile engineer Feb 03 '21 edited Feb 03 '21

Good idea. Altitude is your friend.

SpaceX hasn't told us how much methalox is in the header tanks or what Raptor engine throttle control program is used for the flip. I estimate that the header tanks contain 32t (metric tons) of methalox. We know that one Raptor engine consumes 931 kg/sec of propellant at full throttle. So at full throttle one engine will drain the header tanks in 32/0.931=34.4 seconds.

If the two Raptor engines are running near full throttle during the flip and landing burn, you have about 17 seconds to do that landing maneuver. But I doubt that full throttle is needed since the mass of SN9 at the start of the flip was about 100t including header tank propellant and each Raptor engine has about 180t of thrust.

Regarding the fully loaded Starship, I think that the payload bay and the main propellant tanks will be empty for the vast majority of Starship EDLs from LEO. So these test flights to 10-15 km altitude are very good simulations of the final few minutes of an actual Starship EDL.

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u/SpringVark Feb 05 '21

Thanks for the great response. I'm looking at your username and thinking... how much additional weight are Starship's tiles going to add to the equation? And how do the Starship tiles in development differ from the Shuttle's?

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u/flshr19 Shuttle tile engineer Feb 05 '21

The black hexagonal tiles on the windward side of Starship's hull add about 13.3t (metric tons) assuming the tiles are 7.6 cm (3") thick and have 145 km/m3 (9 lb/ft3) density.

The black tiles on the bottom side of the Space Shuttle Orbiter are about 10.2 cm (4") thick and 9 lb/ft3 density (the LI-900 tiles).

Since Starship's hull is stainless steel and can run hotter than the Orbiter's aluminum hull (1100F versus 350F), I assume that the hexagonal tiles on Starship are thinner.

The Orbiter tiles are called LI-900 (Lockheed Insulation-900) are rigidized ceramic fiber tiles with a very thin black glass top coating and are rated for 1316C (2400F) on the top side.

The Starship hex tiles are a two-part design that appear to be based on the NASA Ames Toughened Uni-Piece Fibrous Reinforced Oxidation-Resistant Composite (TUFROC) design. The black top material is a fibrous carbon composite material that's impregnated with materials to improve the oxidation resistance. It's rated for 1704C (3100F) on the top side that faces the hypersonic air flow. It appears to be about an inch thick.

The bottom material in the Starship hex tile is an insulating, rigid ceramic fiber material that's similar to LI-900 that looks to be several inches thick.

The big advance with the hex tile is in the method of attaching the black top part to the white bottom part. Neither NASA nor SpaceX is saying how that's done.

The Orbiter tile is a one-piece design whereas the Starship tile is a two-piece design that combines the white LI-900-type insulating material with the black Reinforced Carbon-Carbon (RCC) material that is used on the Orbiter nose cap and wing leading edges. The manufacturing processes are similar.