SpaceX Starship Orbital Flight Test

Mr. Musk on several occasions has made the point about the necessity of eliminating elements of a design wherever possible. Just because some element was included in a prior design does not mean it is still required for the current design. Presumably, SpaceX had a discussion at one time about whether a flame diverter would still be required – and a very convincing civil engineer demonstrated by sophisticated extrapolation from limited data that the answer was – No. But extrapolation is always risky, and now SpaceX has demonstrated that – Yes, a flame diverter is still required.

One important question is whether a suitable flame diverter system can be grafted onto the existing Stage 0, versus whether a completely redesigned/rebuilt Stage 0 foundation is required.

Another question is whether all the problems with the Starship flight stemmed from flying debris, versus whether there were additional problems with the rocket itself. Days, nights, & weeks of data analysis ahead for the SpaceX crew!

The bleeding edge of technology is a tough environment. SpaceX deserves a big round of applause for getting this first rocket off the ground. Let’s wish them well for the future.


One of the motivations for dispensing with a flame diverter and trench was that no such facilities exist on destinations such as the Moon and Mars, from which they will eventually want to launch return missions. If they can demonstrate that Starship (without Super Heavy, which is only needed for launches from Earth) can operate from unimproved terrain, that means they don’t have to find a solution for that chicken and egg problem. We now know that “size matters”, and while Falcon 9 can land with one engine on a flat concrete pad with no problems, a 33 engine Super Heavy won’t work. We’ll still have to see how Starship fares on its own.

NASA, in conjunction with Masten Space Systems, was researching a concept called “in-Flight Alumina Spray Technique” (FAST), in which a lander hovers above its landing location while injecting aluminium pellets into the rocket exhaust, where they are liquefied and sprayed onto the surface, creating an instant landing pad where the lander sets down. Unfortunately, on 2022-07-21, Masten filed for bankruptcy after running out of money trying to fulfill a NASA Commercial Lunar Payload Services contract on which they admitted to “grossly underbidding”. I don’t know if anybody else is pursuing the FAST concept. Here is a video about the idea.

One of the first things that will have to be done in establishing a Moon or Mars base will be constructing a landing site for subsequent landings with a surface that doesn’t spray debris in all directions and a berm surrounding it to retain any regolith that does go flying. A lunar lander can eject dust at velocities sufficient to enter lunar orbit and possibly damage spacecraft in orbit, not just sandblast anything in the vicinity.


Apparent owner:


Speaking of missile silos I first ran across the term “stage zero” while writing an AIA article for E’Prime Aerospace on the commercialization of the MX missile. The steam canister spit the missile up into the air which had two benefits: avoiding damage to the ground equipment which could be rapidly reused if necessary and imparting substantial momentum before the first stage booster took over.

For something like the Starship it would have to be quite a steam canister of course.


Fascinating! That is a real issue which will have to be addressed. Long ago, the Apollo missions dealt with this by having a two-part lander and leaving the lower part behind on the Moon, used as a launch pad. But that will presumably not be practical as a long-term solution for the Moon or Mars.

Suggesting launching from Earth without a flame diverter as a precursor to future launchings from the Moon & Mars is definitely the kind of “out of the box” thinking that would be desirable in a brainstorming session. But on analysis it would be found to be a non-starter – soils on Moon & Mars are different from Earth, as is gravity and atmosphere; even if it is possible to launch from an unimproved site on Earth, that does not necessarily mean it would also be feasible in the very different conditions on the Moon & Mars. Besides, no-one is suggesting launching from a totally unimproved site on Earth, not even SpaceX. If that really was a factor in the decision to dispense with a flame diverter, then I would be tempted to agree with CW’s characterization of the decision as an “error in judgement”. SpaceX had enough information at the time to make a better decision.

Just speculation: perhaps the major driver was government regulation. SpaceX was already heavily invested in Boca Chica when they began the planning for Stage 0. They may have realized that building a proper flame diverter would have triggered even more EPA delays because of the shallow ground water, and therefore decided to save time by trying to do without one. ???


Building a Saturn V style flame diverter and trench would have posed the same problems NASA faced at Merritt Island in Florida, where the water table was less than one half metre below the land. NASA built what amounted to a truncated pyramid 16 metres high at each of the launch pads with a ramp on one side that the crawler could ascend to deliver the launch platform and mobile service structure. The flame trench was excavated from the compacted soil of the pyramid and the flame diverter placed below where the launch platform was placed. This did the job for the Saturn V and later the Shuttle and SLS. Super Heavy, however, has twice the thrust of the Saturn V, so everything may have needed to be scaled up.

This would have been a massive civil engineering job and would have taken a long time just to compact the fill material to build up the pyramid. Since Boca Chica Wildlife Refuge borders the site, heaven knows how many forms would have to be filled out and hoops jumped through to build something like that.


Basically, they could build an above ground pool around the OLM. they could still use the crane to swing the Superheavy and Starship into place.


Is it an unimaginable engineering feat to build large-diameter metal (or whatever strong enough materials, assuming they exist) tunnels beneath the water table to contain and divert the exhaust gases laterally into the surrounding atmosphere - without impinging directly on the ground water? Maybe a job for The Boring Company? I’m not an engineer, so forgive me if this is absurd. I’m trying to think out of the box.


Let’s hope there are large numbers of people also trying to come up with solutions – but it is tough to see what those solutions might be. Boca Chica may simply be the wrong site, even if SpaceX had a NASA-type budget. Moving to another site might end up being the only cost-effective solution – but where? Presumably it would be best to be on a coastline as close to the Equator as possible.

Is someone on President Xi’s staff preparing a proposal to help SpaceX build a launch site on Hainan Island? If not, why not? What about New Zealand? Or a Joint Venture with Arianespace at their French Guiana spaceport?


More scratching around on the question of a better site for SpaceX than Boca Chica – or Cape Canaveral with the current soil excavation method of launching Starship.

Perhaps the ideal (relatively) low cost geological environment would be a raised beach on an eastern coast facing the Atlantic or Pacific Oceans, not too distant from the Equator. Raised beaches are sedimentary platforms around 25 to 100 feet above current sea level, left behind over geological time when the sea level retreated (or the land mass rose). Put Megazilla on the raised beach and dig a flame trench pointing towards the ocean and Bob, as they say, is your uncle.

There are famous raised beaches on the West Coast of Scotland – but that is the wrong side of the ocean, since the aim is to take advantage of the Earth’s rotation by launching towards the east. A quick scan through Google Scholar indicates lots of geological investigations of raised beaches in Antarctica and on the west coasts of Africa & South America – wrong places. There are raised beaches on the east coast of Canada, but that may be too far from the equator for efficient launching.

Still looks like the best option for Musk (as already a major investor in China through Tesla) would be to explore what subsidies and regulatory bypasses would be available for a launch site on Hainan Island.


I guess habitability of the area for the workers is also an important consideration. I wonder, for example, how they do it for workers in French Guiana? I don’t imagine it rivals living in La Belle France. I also guess much of the work demands utmost skill and cannot be done remotely.


In the early morning of 2023-04-30 (UTC, evening of the 29th in the Western Hemisphere), Elon Musk held an hour long Twitter Spaces conversation, “Starship”, co-hosted by Tim Dodd of Everyday Astronaut. This was a “Subscribers Only” event, so the link above will work only if you’ve signed up to pay Elon US$ 4 (why not 4.20?) a month for his special subscriber content because—he needs the money.

Michael Sheetz, who does subscribe, tweeted items he found worthy of note in the discussion, which have now been collected into a Thread Reader App document. Here are some of the remarks, all quotes from Elon Musk.

Musk: “The outcome was roughly in what I expected, and maybe slightly exceeding my expectations, but roughly what I expected, which is that we would get clear of the pad.”

Musk: “I’m glad to report that the pad damage is actually quite small” and should “be repaired quickly.”

Musk: “The vehicle’s structural margins appear to be better than we expected, as we can tell from the vehicle actually doing somersaults towards the end and still staying intact.”

Musk: From a "pad standpoint, we are probably ready to launch in 6 to 8 weeks.’

“The longest item on that is probably requalification of the flight termination system … it took way too long to rupture the tanks.”

Musk: Time for AFTS [Autonomous Flight Termination System —JW] to kick in “was pretty long,” about “40 seconds-ish.”

Musk: “There were 3 engines that we chose not to start,” so that’s why Super Heavy booster lifted off with 30 engines, “which is the minimum number of engines.”

The 3 engines “didn’t explode,” but just were not “healthy enough to bring them to full thrust so they were shut down”

Musk: At T+27 seconds, SpaceX lost communications due to “some kind of energy event.” And “some kind of explosion happened to knock out the heat shields of engines 17, 18, 19, or 20.”

Musk: “Rocket kept going through T+62 seconds” with the engines continuing to run. Lost thrust vector control at T+85 seconds.

Musk: Generated a “rock tornado” under Super Heavy during liftoff, but SpaceX does not “see evidence that the rock tornado actually damaged engines or heat shields in a material way.” May have happened, but “we have not seen evidence of that.”

Musk: Reason for going with a steel plate instead of a flame trench is that for payloads in the rocket, the worse acoustic environment doesn’t matter to the payload since it’s about 400 feet away.

Musk: “Definitely don’t” expect lunar Starship (under the HLS project) to be the longest lead item for the Artemis III mission.

“We will be the first thing to really be” ready.

Musk: Probably an 80% probability of reaching orbit with Starship this year, and “I think close to 100% chance of reaching orbit within 12 months.”

Read the whole thing.

Jeff Foust of SpaceNews has posted a summary, “Musk predicts next Starship launch in a ‘couple months’ ”.


I may have lost context, but that seems like very bad news. If true, they now have to track down causes of the engine failures.


He says that they lifted off with three engines which the monitoring system decided not to start because of health monitoring. Thirty engines is the minimum number to commit to liftoff. The “explosive event” at T+27 seconds destroyed the heat shield of engines 17, 18, 19, or 20. Then, around 60 second, there was another explosive event which damaged the heat shield around engine 30. He does not speculate on the cause of the explosive events.


Interesting statement by Mr. Musk:
"Musk: For the next flight, “we’re going to start the engines faster and get off the pad faster.” From engine start to moving Starship “was around 5 seconds, which is a really long time to be blasting the pad.” Going to try to cut that time in half. "

Presumably he means they will attempt to throttle up the engines faster. Since probably most of the damage to the site is done when the engines are at full throttle, that may not help with the Rapid Unplanned Digging issue. A lot is riding on that water-cooled steel plate!

Interesting also that 10% of the engines were deemed to be not up to being started. That seems like rather a high failure rate for engines that are intended to be reused at a high launch cadence rate. Lots of work ahead there!


They ripple-start the engines to avoid an additive shock effect as the engines light. This is common in clustered engine configurations. Here is the start-up sequence of the five engines of the Saturn V first stage.

The three engines of the Space Shuttle orbiter were ignited 120 milliseconds apart for the same reason.

I don’t know the engine start sequence for Super Heavy, but they have said the ignitions are spaced out over time. It may be possible, however, to tighten up the time between start events and/or start more engines, presumably separated by space but symmetrically, at the same time to reduce the length of the start sequence. This would also be advantageous for performance, since any fuel you burn prior to release of the rocket for flight contributes nothing toward delivering the payload.


Everyday Astronaut has taken the 8K resolution 90 frames per second video of the portion of Starship’s flight between activation of the Flight Termination System and the eventual explosion, hand-stabilised it frame-by-frame, then rotated the images to take out the tumbling of the rocket as it fell. This was posted as a Twitter video, which cannot be embedded here, so you’ll have to click the link to view it.

In this imagery, you can clearly see the plumes of propellant released from the holes in the tanks blown by the flight termination pyrotechnics and how the ship was rolling around its long axis in addition to tumbling in the upper atmosphere. In the Twitter Spaces conversation, Elon Musk said they will have to install something like linear shaped charges to rip the tanks open and disperse the propellant faster than what was installed on this flight.

Since this imagery was captured at 90 frames per second, it is slow motion compared to real-time events in the flight. Musk said the time between activation of the flight termination system and break-up of the ship was around 40 seconds.


So many different factors to balance & compromise in launching a rocket!

From the Saturn V example, it looks like all engines were at full power about 1 second before launch. If SpaceX’s aim is to cut the burn time before launch to 2.5 seconds (cf nearly 3.5 seconds for Saturn V), that would mean firing up all the engines in the space of about 1.5 seconds – 1,500 milliseconds. If SpaceX can fire up the engines 3 at a time, distributed around the vehicle, that would give them about 150 milliseconds between lighting up each group of 3, which would be comparable to the Space Shuttle ignition schedule. It is always comforting when something has worked before!

As Mr. Musk said, this is probably one of the most technically-challenging tasks the human race has ever attempted. But I do find myself wondering about the foundation loads on a major bridge, and how that partly static/partly slow transient load compares to the rapid transient load underneath Stage 0. Faced with all the many rocket science challenges, perhaps SpaceX under-invested in plain old civil engineering?



I worry the steel plates will get lifted and tossed intact