Following the maiden launch of the world’s most powerful rocket, SpaceX hopes to conduct a mirror test flight of the Starship rocket this summer.
Several requirements need to be satisfied before the flight of Booster 9 — and a to-be-decided Ship partner — ranging from repairing and improving the launch site to modification to the flight termination system (FTS). However, the launch of Booster 7 and Ship 24 achieved numerous objectives to add confidence in the system and provide a stepping stone to the key milestone of Starship reaching orbital velocity.
Booster 7 and Ship 24’s spectacular launch from Starbase was achieved with a vehicle already out of date.
Via a year of pad tests, rollbacks, modifications, and cryo cycles, Booster 7 still lacked numerous improvements already implemented on the next vehicle to fly, Booster 9.
Before the flight, SpaceX Chief Designer Elon Musk set expectations accordingly, ranging from not destroying the launch site via a pad explosion to gaining as much data as possible.
“If we get far enough away from the launch site before something goes wrong, I’d consider that to be a success,” Musk said ahead of the launch during a Twitter Spaces call to his subscriber base, also agreeing that passing MaxQ would be a win. “Just don’t blow up the launch pad.”
The vehicle did clear the Tower, but the full power of Booster 7’s liftoff thrust caused a “rock tornado” that spewed debris far and wide, impacting numerous structures, including the tank farm.
“The outcome was roughly in the sort of what I expected. And, maybe slightly exceeding my expectations, but roughly what I expected, which was or, or hoped for, I should say. Which is that we would get clear of the pad with minimal damage to the pad,” noted Musk post-flight.
“I’m glad to report that the pad damage is actually quite small and looks like it can be repaired quickly.”
Launch Site Status
It was hoped the pad could cope with liftoff ahead of planned modifications, based somewhat on the 31-engine static fire test of Booster 7. However, that was at 50 percent of the rated thrust, and the ramp-up for launch proved too much for the concrete surface during the six seconds before being committed to liftoff.
“Obviously, the rocket stayed on the launch pad for a while. And, we did generate quite the rock tornado at the base of the vehicle. And, our first guess would have been that the rock tornado would have caused potentially significant damage to the engines.”
“Weirdly, we did not see evidence of the rock tornado actually damaging engines or heat shields in a material way. It may have, but we have not yet seen evidence of that.”
Ahead of the next flight, SpaceX will fill in the crater — which is already near-complete as a task — that resulted from Booster 7’s liftoff and cover it in a water-cooled steel plate. This pre-planned modification will now be completed at the launch site.
“We’re going to be putting down a lot of steel. The debris is really just sand and rock, so it’s not toxic at all or anything. It’s like a sandstorm, essentially — basically a human-made sandstorm. But, we don’t want to do that again, so we’re putting down a very strong steel sandwich that is basically a water-jacketed sandwich.
“It’s two layers of very thick plate steel that are also sort of perforated on the upper side so that you have what is basically a massive, super strong steel showerhead pointing up. And then, the water pressure coming out of there has to exceed the pressure that the engines’ thrust is exerting on the steel plate on the vehicle launch stand.
“It’s a mega steel pancake. This thing’s a beast. You’ll see it come together in the next month or so.”
Another mitigation will be a change to the final seconds of the countdown. During the maiden launch, Starship fired up its engines over a 5-6 second period. Musk added that during Booster 9’s launch, this will be reduced by around 50 percent — to around 2.5 seconds — before the vehicle lifts off.
“So, for the next flight, we certainly will be taking off faster. For this flight, we erred on the side of babying the engines and just sort of gently starting each engine one at a time.”
Thankfully, the initial reports of the launch site in the days after the launch have been positive.
“We’re glad to see that there appears to be minimal damage to the launch ring and the components inside the launch ring. So, that’s great because that launch ring, you know, it takes six months to build up a new launch ring,” added Musk.
“We have some spares, but there’s a lot of complex plumbing and wiring inside the launch ring, and that actually appears to be in good shape.
“We’re going to be replacing a bunch of the tanks in the tank farm. But, these are tanks that we wanted to replace anyway.
“We’re going with more of the vacuum jacketed, kind of giant hotdog-looking tanks. The vacuum-jacketed giant tanks, those are in the best shape, and those are what we want anyway.
“The Tower itself is in good shape. We see no meaningful damage to the Tower, even though it did get hit with some pretty big chunks of concrete.”
The Maiden Launch
Starship took flight during what was only the second launch attempt, following a scrub due to a valve issue just days prior.
Musk explained that the launch took place with 30 engines running instead of the full set of 33.
“There were three engines that we chose not to start, or hit aborts. (So), we actually lifted off with 30 engines, which is the minimum number of engines.
“Those engines did not explode, but they were just, the system didn’t think they were healthy enough to bring them to a full thrust,” added Musk during a post-flight Twitter spaces call, adding that is why the vehicle appeared to lean away from the Tower during ascent.
It was assumed the lean could have been related to pad avoidance, but Musk quickly noted that it is undesirable due to the “blowing torch” of the Raptor 2 engines on the OLM ring.
“If you move sideways sooner, you are moving that big, cutting torch across the launch ring. So, you can think of this thing like the world’s biggest cutting torch, basically. Depending on how close the engines are, they erode that steel at a roughly — I think half an inch to an inch per second of high strength steel is eroded by the cutting torch.”
“(The lean was actually) related to the engines out, and we do not normally expect to lean. It should be aspirationally going straight up.”
As Starship thundered into the South Texas skyline, cameras picked up flashes and heat shield liberations from the engine section.
“At T+27 seconds, engine 19 lost communications, concurrent with some kind of energetic event that liberated the outer heat shield from the engines,” added Musk.
“(This was from the engines) 17, 18, 19, and 20 areas. So, something bad happened at T+27 seconds because engine 19 lost communications and some kind of explosion happened to knock out the heat shield (in that area).”
A bonus from these off-nominal events was gained by the vehicle continuing to push through its launch without any apparent ill effects, such as its trajectory.
“There were visible fires seen from the aft end starting after this event and continuing through flight. The rocket kept going, though. At T+62 seconds, we see additional aft heat shield damage near engine 30. However, the engine continues to run.”
While Starship is capable of running with multiple engines down, Musk had already noted the concern of engines letting go in the aft during launch, describing it ahead of the launch as “if anything goes wrong, it’s like having a box of grenades, but really big grenades. So, if one of those grenades goes off, you don’t want the other grenades to go off too.”
Thankfully, the “retrofitted” blast shielding — which has been tested already at SpaceX’s test site in McGregor, Texas — provided a good amount of protection to the aft of the rocket as a whole, adding confidence in what will be major improvements to the shielding on Booster 9.
“At T+85 seconds is where things hit the fan. We see engine six with a loss of communication to thrust vector control. And, roughly from this point onwards, we lose thrust vector control of the rocket. So, we lose steering at T+85 seconds.
“There appears to be perhaps a flame path somewhere within the vehicle structure that as some of the engines failed; there may have been, there would appear to be a flame path to a piece of avionics or control system that knocked out the thrust vector control.”
The loss of the TVC resulted in Booster 7 losing steering authority, which in turn led to the rocket starting its tumbling motion. The Flight Termination System (FTS) was activated soon after the vehicle started to tumble, but it failed to destroy the vehicle. Therefore, this item will require additional modifications before the next flight and is deemed the long lead item.
“The longest lead item on that is probably the requalification of the flight termination system. Because we did initiate the flight termination system, but it was not enough to, it took way too long to rupture the tanks,” Musk noted.
“So, we need basically a much — we need more detonation cord to unzip the tanks at altitude and ensure that the rocket explodes immediately if a flight termination is necessary.”
An ironic byproduct of the rocket failing to die when the FTS was triggered was the structural margins on the vehicle. The still-integrated stack held together for around 40 seconds before succumbing to its wounds from the FTS being triggered and the aerodynamic stresses.” As you can tell, the vehicle is actually doing somersaults toward the end and still staying intact. The aerodynamic forces would have, I think, at a lower point in the atmosphere, aided in the destruction of the vehicle,” noted Musk.
“The atmospheric density was enough to cause structural failure. But, I mean, this is obviously something that we want to make super sure is solid before proceeding with the next flight.”
“The vehicle’s structural margins appear to be better than we expected.”
Addressing why the vehicle didn’t stage to give Ship 24 a fighting chance of having its standalone test, Musk noted they got close and may have achieved it if they had kept the TVC ability despite engines failing.
“It got pretty close to stage separation. So, if we had maintained thrust vector control and throttled up, which we should have, because we needed to compensate, we’d lost too many engines, so we needed it to — we should have throttled up the remaining engines to make up for the missing ones.
“If we’d throttled up the remaining engines and maintained thrust vector control, we would have made it to staging.”
The lack of staging was due to the Ship’s requirement to make it to its designated abort point in the event of a failure during its flight and the Hawaii splashdown point had it achieved its required burn.
“The problem is that we have a very precise targeted entry point in the Pacific. So, the Ship really wouldn’t have the delta velocity or the capability of reaching that target point. So, it would only be worth really starting the Ship if the Ship is able to complete its mission and reach its targeted landing point just west of Hawaii.”
Next Up: Booster 9 and Ship X
Musk had already noted before the flight that Booster 7’s flight was just about data gathering, with many modifications already employed on future vehicles.
“This is the first step in a very long journey that will require many flights,” added Musk. “Because we’ve made so many improvements in Booster 9 and beyond that, we really just needed to fly this vehicle and then move on to the much-improved Booster 9 and later ship designs.”
In the preflight Twitter Spaces, Musk had already referenced this forward path, citing the next Booster being a major step on the evolution path.
“There are so many improvements from Booster 7 to Booster 9, literally hundreds, some major ones. We’ve moved from hydraulic TVC to electric from Booster 7 to Booster 9. The entire heatshield structure on the base is completely redesigned.”
These changes, along with Booster 7 getting past MaxQ and almost to staging, add confidence in the next attempt with Booster 9.
“I think we’ve got a better than 50% chance of reaching orbit on the next flight. So, I’d say that my expectation for the next flight would be more likely to reach orbit than not,” Musk noted in the post-flight Twitter Spaces.
“We’re just going to do repeat, basically. The goal of these early missions is just information. Like, we don’t have any payload or anything. We just try to learn as much as possible. And so, that’s why I would consider this to be a success because since the goal of the flight was to learn a lot, and we learned a lot, I would characterize it as a success. Obviously not a complete success, but still nonetheless successful.”
With numerous vehicles already in various stages of production at the build site, SpaceX hopes to pick up the pace as they continue to learn how to fly with this new system and reach the goal of making it to orbit.
“I’m hoping we can get four flights out this year, maybe five. And, we should; I would be surprised if we exit this year without getting to orbit. I think it’s a, not a 100% probability, but we’ve probably got an 80% probability of reaching orbit this year.”
“The thing to bear in mind is SpaceX is actually quite good at production. So like, like extremely, like the best in history of any rocket maker with production. I mean, we’re making a Falcon 9 upper stage, which is a large complex machine, every three or four days.”
The Ship that will fly with Booster 9 is yet to be chosen. Ship 25 is currently at the Masseys test site near the Production facility, while Ship 26 and 27 are “naked” vehicles without any Thermal Protection System (TPS). Ship 28 is in the High Bay and sports the aero surfaces seen on Ship 24, which are also included on Ship 25.
Based on the clues provided by Musk during the Twitter Spaces, it is likely Ship 28 may be chosen to fly, given the repeat objectives that include re-entry data and the wish to move on to “future” designs.
“We’ve not made a final decision on the Ship. That’s why I was referring to Booster 9, but I was somewhat I did not mention the ship number. So, a good catch there,” added Musk in response to NSF. “I think we’ll probably make that decision this week.
“It would be super to try to deorbit and see how well the ship heat shield works. Because we need to maintain control in hypersonic, high heating regime, then get through transonic, and then, you know, maintain control all the way through a very wide array of mach regimes.
“And so, the vehicle actually behaves differently with radically different heating and force at the various, you know, coming back from like roughly mach 23 to 0. So, I think we’ll put a ship on that gives us that capability. But, we haven’t decided exactly what ship number it should be.”
Musk also added context to this entire Starship program by thanking the team involved and noting just how much of a challenge is being undertaken with the most powerful rocket in history, and one that is set to be fully reusable.
“I thought the SpaceX team did amazing work. This is really one of the hardest technical projects that humanity has ever done. I mean, if you say, like, fully reusable, humongous rocket, fully and rapidly reusable, reliable Rocket Of Unusual Size.
“But, this is certainly a candidate for the hardest technical problem done by humans. It’s a candidate, you know.
“So, I think the team’s done excellent work on a very hard problem. I’m upbeat about the next 12 months. I think we’re going to get to orbit.
“And then, it’ll probably take us a few more years to achieve reusability on a regular basis where we bring the booster back and bring the ship back and where it gets, you know, it’ll take a few years to get to where Falcon 9 is today, where it is now quite normal for the rocket to land.”
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(Lead Image: Starship doing somersaults. Credit: Max Evans for NSF/L2)