BOCA CHICA, TX – The first full-scale Starship prototype for SpaceX has finally completed its cryogenic pressure test! What exactly does that mean and what’s up next? We’re talking about that today.
It’s been a while since we’ve talked about SpaceX’s Starship prototype development so let’s get everyone up to speed. First if you’re not familiar with what the Starship is, this is the next generation rocket that SpaceX is developing to send people to the Moon or Mars it was previously known as the Interplanetary Transportation System or ITS. It was then renamed to the Big Falcon Focket or the Big F***ing Rocket or just BFR for short. After that they renamed it again to the Starship and Super Heavy launch vehicle. The Super Heavy is the first stage booster of that rocket and the Starship is the upper stage where people will ride.
Last year in 2019 we saw the development of that lovable flying water tower known as Starhopper. Star Hopper completed a couple of hops (test flights), but finished its test campaign in August of 2019. After that SpaceX moved on to full-scale prototypes the first of which we saw back in September 2019 when Elon Musk did a public presentation displaying the mk1 Starship prototype down in Boca Chica, TX. At that presentation Elon Musk said that that mk1 prototype would be ready to perform an ambitious 20 kilometre test flight in about a month or two.
“Our plan is in basically 1 to 2 months to do the the 20 kilometer or 65 [thousand] foot flight with Starship mk1”
-Elon Musk, September 2019
Now for anybody keeping score at home it’s been about seven months and it hasn’t flown yet, but that’s okay because a lot has changed since then. As you might imagine from that seven month delay, SpaceX has had a little bit of trouble along the way scaling up their platform from the Starhopper days to the full-scale prototype. You can’t really blame them, though. After all, this is a development platform and unexpected issues are… expected.
Leading up to the successful test from earlier this week, SpaceX has specifically had issues with cryogenic pressurization tests on their fuel tanks. The mk1 prototype that we saw back in September kicked off the boom town celebrations back in November 2019 during a cryogenic pressurization test when it failed.
Starship Mk1 has failed cyro pressure testing. That is why you test. It is just a prototype. They will fix it and move on. #SpaceX
(via @LabPadre)https://t.co/g9p6YXU9wK pic.twitter.com/ShJeCZonGG
— Michael Baylor (@nextspaceflight) November 20, 2019
This overpressurization event was actually kind of expected, because SpaceX was attempting to bring the prototype to max pressurization so a failure and overpressurization event was not exactly unexpected. They’d already decided not to fly the mk1 prototype, because they had already made so many design changes that a future version would probably be better suited for flight tests. That mk1 prototype obviously never flew. Then, the mk2 prototype which was being built in Cape Canaveral Florida was eventually cancelled so they could focus their efforts in Boca Chica, TX and speed up development.
That brings us to the mk3 prototype which SpaceX actually changed up the naming structure on us and started calling that serial number one or SN1. SN1 was built and rolled out to the test pad back in February 2020 and that failed spectacularly.
#Space_News: SpaceX’s #Starship SN1 prototype has blown up during pressure test. Initial reports have implied that the tank may have suffered a structural failure during pressurisation.#SpaceX #BocaChica pic.twitter.com/K8sGRADlZk
— BIS (@BIS_spaceflight) February 29, 2020
I’m sure that SpaceX would not use that terminology, but let’s just say it was a crazy sight.
After the failure of SN1, SpaceX would move on to SN2 which was actually a smaller tank test and not a full-scale test. SN2 was actually the first to pass the cryogenic pressurization test, but it wasn’t full-scale. For that they had to pull out SN3 which would be the next full-scale prototype. SN3 performed that test just a couple of weeks ago at the beginning of April 2020 sadly that vehicle also failed when it appears that the liquid oxygen tank buckled under the weight of the methane tank that was up on top.
#SpaceX’s #Starship SN3 prototype rocket CRUMPLES like a tin can as it fails latest test https://t.co/dqMcDmSvMB pic.twitter.com/HeWViEcCez
— RT (@RT_com) April 3, 2020
Elon Musk mentioned on Twitter that this failure was actually a test configuration failure and not a failure of their design. That’s relatively good news in that they don’t have to go back to the drawing board. They can just fix the test for next time and that next time happened just a couple of days ago with SN4.
Pretty much. Good news is that this was a test configuration error, rather than a design or build mistake. Not enough pressure in the LOX tank ullage to maintain stability with a heavy load in the CH4 tank. This was done with N2.
— Elon Musk (@elonmusk) April 5, 2020
SN4 first had to pass an ambient pressure test which it did and then it moved on to cryogenic pressurization. That pressurization test came on Sunday, April 26, 2020 where it successfully passed by reaching 4.9 bars which is enough to fly with.
SN4 passed cryo proof! 😅 pic.twitter.com/EJakThZRGF
— Elon Musk (@elonmusk) April 27, 2020
In order for that Starship prototype to be classified for orbital flights it will need to pass a pressurization test getting up to six bars of pressure. Beyond that, if Starship wants to fly humans, it’s going to need pressurization of up to eight and a half bars. However, let’s not get ahead of ourselves here. There are still a lot of design changes happening with the Starship prototype. Elon Musk has said that they’re already changing metals & they’re redesigning the thrust dome so things could change drastically just in the coming weeks.
Yes, switching soon to a 300 series alloy with higher ductility at cryogenic temp. 301 is good as sheet, but not as plate. Also, a lot of geometric changes.
— Elon Musk (@elonmusk) April 26, 2020
It’s a little dicey tbh. Thrust dome is being redesigned. Current one has four separate layers of steel in some places!
— Elon Musk (@elonmusk) April 26, 2020
Next up for the SN4 vehicle will be a static fire test where they mount one Raptor engine to the bottom of that vehicle and then fire the engine while holding it down to the ground. If it successfully performs the static fire, SN4 could be the first candidate to fly a 150 meter hop or test flight. The SN4 Starship prototype could be physically ready to perform that 150 meter hop within just a few weeks, but whether or not the FAA is ready to give approval for that flight test is another story. That could take a couple of weeks too.
SN4 is only going to be capable of performing smaller hops, because it doesn’t have any control surfaces on it and Elon Musk has said that there is no intention to put control surfaces on SN4. That functionality will be reserved for SN5 or maybe SN6 later down the road as they’ve already redesigned their control surfaces. Starting with SN5 or maybe SN6 those will be the first candidates that will have three Raptor engines on the bottom and be capable of flying the twenty kilometer test flight.
Just one. SN5 will get three.
— Elon Musk (@elonmusk) April 27, 2020
One thing’s for sure and that is the speed at which this development is taking place and the fact that we can watch it all is pretty awesome! Don’t forget we have the DM-2 flight which is the first crewed flight with astronauts flying onboard the Falcon 9 up to the International Space Station coming up at the end of May!
I want to know which project of SpaceX you’re looking forward to most! Are you looking forward to Starship? Crew Dragon? Starlink internet? Let me know!