TexAgs91 said:
Kceovaisnt- said:
So the only issue is durability of the pad under the OLM.
Not just under the OLM. Remember boosters and starships will be flying back to the pad. While it's true it won't be as much thrust as a launch the area surrounding the OLM will still need to be hardened as well.
I am not convinced this will be an issue at all.
The full stack left the pad with about 1.3 thrust to weight ratio. That approximates to above 10 million lbs of thrust. For about 5 full seconds before liftoff firing 31 engines at launch on the pad at about 60 ft above the pad surface which was Fondag. Thrust was likely closer to 12 million lbs but let's assume just over 10M.
When the Booster attempts a landing at the launch site, it will ignite 5 of the 10 inner ring engines along with the center 3 engines for the landing burn. Before the Booster even approaches the launch site and has finished the bulk of it's deceleration, it will cutoff the 5 inner ring engines and land with nearly empty propellant tanks with only the center 3 Raptor 2 engines running at throttled power around a 1.0 thrust to weight ratio. So, that's about 450 thousand lbs of thrust. It will land about 250 ft above the pad surface and the engines should cutoff just after the vehicle comes to a rest on the chopsticks.
So that's 3 engines at landing compared to 31 at liftoff, approx. 5% total thrust at landing compared to liftoff, and around 4x the height off the pad surface as compared to liftoff.
These are huge factors.
We see the damage that resulted from the 1st test flight of the full stack. We have also seen 6 engine static fires from Ship 24 on the suborbital pad about 20 ft above the pad surface which I think is plain concrete for about 5 seconds. Although it DID have a small deluge system. Also that pad has seen suborbital launches with 3 engines and about 25% propellant load for suborbital test flights with no deluge. Although, those were Raptor 1 engines. No major issues on the pad on those tests other than bit of spalling
I don't see the need to beef up the pad or surrounding areas for landings at the launch site.