SpaceX launched its Starship rocket amidst much fanfare and anticipation earlier this week. The rocket, which took off without any protection for the launch site, left a massive crater in its wake and destroyed the base of the launch tower. With the proverbial 'dust' clearing up after the historic launch, speculation is rife about why the first and second stages of Starship were unable to separate after liftoff, with some even suggesting that the rocket has to 'flip' before the second stage separates to provide the latter with enough force to race away from the Super Heavy booster safely.
Elon Musk Admits SpaceX Miscalculated The Impact of Starship Launch On Pad Concrete
SpaceX's Starship rocket uses 33 engines to liftoff, making it the world's only super heavy rocket right now, apart from NASA's Space Launch System. This makes the rocket generate millions of pounds of force, greater than NASA's Saturn V rocket that sent humans to the Moon. While the Falcon Heavy is also rated to launch more than 50 tons to orbit (NASA's official classification for a super heavy rocket), it is yet to launch such a payload despite being operational for several years.
Starship's thrust, stated to be a whopping 17 million pounds, makes the rocket capable of lifting a stunning 250 tons to low Earth orbit (LEO) if its upper stage is expendable. The thrust also requires shielding on the launch site, and SpaceX's decision to launch it without the shielding earlier this week made the launch site appear as if a bomb had ripped through it.
Footage from several sources showed a massive crater at the base of the launch tower. The orbital launch mount (the 'stand' for the 394 feet tall rocket) was unrecognizable after the smoke cleared and footage of the launch site made rounds on the Internet.
Starship’s launch pad after its test flight yesterday. Yikes.
Perhaps surprisingly, a sustainable launch pad may be the bottleneck for Starship’s success. SpaceX will have to consider what changes must be made before next launch. Perhaps flame diverter or stronger water deluge. pic.twitter.com/vrY6gwH2kX— Toby Li (@tobyliiiiiiiiii) April 21, 2023
Images of the launch pad show that all of the concrete under it was blown away by the rocket, as the land and dirt under it are clearly visible. Independent cameras covering the event revealed massive dust clouds and chunks of concrete flying through the air immediately after launch close to the pad, with residents in the nearby Port Isabel reporting 'gunpowder-like' dust falling from the sky and covering vehicles.
Naturally, this force of the impact should have been predicted by SpaceX - at least due to a potential effect that it might have had on the orbital test launch. The FAA had granted SpaceX permission to launch only one flight, raising the stakes even higher for a launch attempt.
In fact, speculation is rife on internet forums about the launch pad mishap causing the rocket's first and second stages to fail to separate after it had crossed the point of maximum aerodynamic pressure. While the launch was a success simply because Starship flew as far as it did, the fact that the pad (and not the rocket) might have contributed to the upper stage not making it to orbit is a bit of a letdown. There is some speculation that chunks of concrete from the pad damaged the rocket's engines and maneuvering systems, preventing it from accurately maintaining flight trajectory and crucial maneuvers.
Additionally, unverified sources on internet forums claim that Starship has a pretty radical design for stage separation. SpaceX's Falcon 9 sees the first and second stages separate through a pusher mechanism that ejects the second stage after the booster's outer ring engines are turned off. As opposed to this, Starship will instead 'flip' at a stunning 270 degrees using the inner engines capable of gimballing, and at this point, the inner engines will turn off, and the Starship's second stage will separate.
This theory is also bolstered by SpaceX's presenters John Insprucker and Kate Tice during the launch test. At the 2:47 mark, ground control teams confirmed booster engine cutoff, but footage of the launch still showed that some of the engines were still firing, with Mr. Insprucker announcing that Starship was "beginning the flip for stage separation."
After this, the rocket completed almost two 'rotations,' but Tice sounded quite calm at the 3:23 mark when she simply shared that SpaceX was "waiting for stage separation." This suggests that a flip as part of stage separation was expected during the launch. At this point, the booster's engines continued to fire, and Insprucker added roughly ten seconds later:
Yeah Kate right now it looks like we saw the start of the flip, but obviously we're seeing from the ground cameras the entire Starship stack continuing to rotate. We would have had separation by now. Obviously, this does not appear to be a nominal situation.
Coming back to the pad damage, SpaceX's chief Mr. Elon Musk admitted that his firm had underestimated the damage that might occur to the pad during a full-scale launch. Musk shared in a tweet:
3 months ago, we started building a massive water-cooled, steel plate to go under the launch mount. Wasn’t ready in time & we wrongly thought, based on static fire data, that Fondag would make it through 1 launch. Looks like we can be ready to launch again in 1 to 2 months.
He added that the flames of the Raptor engines shattered the concrete instead of eroding it - insinuating that perhaps SpaceX had expected the latter to occur. A water-cooled steel plate would have water flowing under it to remove the rocket's heat. Designing a rocket launch pad is complex, affecting the mass that can be carried to orbit. This is because the vehicle has to be strong enough to withstand the shockwave that reflects off the ground and runs up the rocket's sides. Adding strength means adding more mass, which then reduces the payload capacity.
source https://wccftech.com/spacexs-starship-launch-was-like-a-bomb-destroying-the-launch-pad/