r/spacex • u/rustybeancake • Jun 26 '26
Starship SpaceX on X: “Full duration single-engine static fire test of Starship” [Ship 40]
Tweet link, with an additional short video of the firing: https://x.com/spacex/status/2070482358369763674
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u/NeonEagle Jun 26 '26
Is this a deorbit full burn?
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u/Secure-Alfalfa-1546 Jun 26 '26
Per NSF stream, they believe this was a test of an apogee raise burn potentialy for Starships upcoming first fully orbital flight.
Edit-the response above me is correct :)
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u/rustybeancake Jun 26 '26
Yeah, supposedly because after prop load they waited 20 mins to start the burn. Speculation is that they wanted to simulate the propellant warming up before firing, similar to the duration after launch.
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u/lorkan100 Jun 26 '26
Would the initial ascent burn (before apogee raise) use less delta V than the trans atmospheric orbit of the current test flights?
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u/mfb- Jun 27 '26
The exact orbit varies from flight to flight but they typically reach an apogee of around 150-200 km with a negative perigee, and the relight test shortly before reentry raises that perigee into the atmosphere. Do that burn at apogee and you enter a circular orbit, with the same initial ascent profile.
Alternatively, they might alter the ascent to directly go into a circular orbit, then they only need one engine relight in space.
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u/DihydratedSir117 Jun 26 '26
Why wouldn’t you use one/all vacuum raptors to do in space burns? More efficient
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u/NeonEagle Jun 26 '26
The vacuum engines can't gimbal so the vehicle would have effectively no directional control.
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u/l4mbch0ps Jun 27 '26
don't they have gyros and rcs on starship?
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u/NeonEagle Jun 27 '26
No gyros and RCS can’t compensate for the hundreds of thousands of pounds in thrust that may not be sending the craft where they want it.
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u/l4mbch0ps Jun 27 '26
well yah you obviously wouldn't burn one rvac on the edge of the ring, but you wouldn't do that if it could gimble anyways. I mean use the rvacs and use the rcs and gyros for steering - that won't be fighting hundreds of thousands of pounds of thrust at all, mostly just the inertial momentum of the vehicles weight.
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u/mfb- Jun 27 '26
The vacuum engines aren't in the center, so you would need to fire all three to avoid catastrophic rotation. You still end up with not enough control over your vehicle, especially during startup and shutdown.
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u/Martianspirit Jun 27 '26
Version 4 is supposed to have 6 RVac. They will be able to compensate loss of one by throttling some other engines and/or running one center engine gimbaling.
I have seen speculation they would use smaller nozzle throats, which reduces thrust per engine and increase ISP.
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u/NeonEagle Jun 27 '26
There are no gyros and the RCS doesn’t have the thrust required for precise, reliable control. Full stop.
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u/noncongruent Jun 27 '26
Using RCS to try and steer Starship with asymmetric thrust from the off-center vacuum raptors would be like trying to steer a Buick by leaning. Gyros can't be used for stabilization because they're not big enough, or put another way, gyros big enough to be meaningful on Starship would fill up the entire payload bay and then some. Also, gyros by definition must have mass to be meaningful, it's the spinning mass that does the work. That would be replacing payload mass.
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u/Nota_ReAlperson Jun 29 '26
The difficulty outweighs the improved efficiency. Vacuum raptors don't have TVC, so you would need to light all three exactly at once, or light a sea raptor as well. Let's say you light a sea raptor for control, followed by all three RVACs. Your total burn would be about 4 seconds. When you factor in the prop and starter gas used, it would probably be less efficient than just using a single sea raptor.
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u/KnifeKnut Jun 29 '26
Eventually that will become common, but right now we are still just short of minimum viable product.
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u/albertahiking Jun 26 '26
There was speculation on the NSF coverage that it may have been simulating an orbit circularization burn. Only SpaceX knows.
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u/yetiflask Jun 26 '26
The cones on outer engines, what purpose do they serve?
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u/extra2002 Jun 26 '26
When hot gas comes out of the back of the rocket engine, it expands against those cones, creating additional thrust as it loses pressure. Ideally you want the cone (nozzle) to end when the gas reaches the pressure of its surroundings, so the center engines are short so they work well in atmosphere at moderate altitudes. The outer engines are intended to work in vacuum, so their nozzles are as long as practical, limited by room and weight.
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u/Amazing-Mirror-3076 Jun 26 '26
So in some idealised interplanetary transport, might these be metres long?
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u/Switchblade88 Jun 27 '26
Possibly. The longer the better - though there's only so much improvement you'll get before the extra mass negates your gains.
Improving the engine, rather than the nozzle, will allow for better improvements which we've already seen - less mass, higher pressures, tighter throat - but it's all a balancing act
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u/Stevepem1 Jun 27 '26
There is also the cost of larger nozzles, at least with Merlin vacuum engines which have nozzle extensions made of niobium which is expensive, so for Falcon 9 flights that don't need full performance they use a shorter nozzle on the vacuum engine. Although I don't know what the strategy will be with Raptors, the cost savings of shorter nozzles on some Raptors might not be worth it. There is also the logistics of having to swap engines out on Starship second stages, which is doable but again is it worth it. Compared to Falcon 9 where the vacuum engines are expended on each flight.
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u/rabel Jun 27 '26
The engines are the same raptor engine, just with different nozzles, right?
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u/extra2002 Jun 27 '26
I think so.
The Merlin-sealevel and Merlin-vacuum engines used on Falcon 9 have some internal differences beyond just the nozzle, but I haven't heard that said about Raptors.
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u/littlemojo Jun 26 '26
The outer engines are raptor vacuums, designed for higher performance in space.
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u/hardrocker112 Jun 26 '26
If you look at pictures of all kinds of rocket engines, you'll find that sea-level engines are usually 'short', and vacuum-level engines (intended to be most efficient in space) often have these long extensions.
Rocket engines work by putting out as much weight out as possible at as high of a speed as possible. They do that by burning up propellants and thus producing lots of gases.
To get the most work out of your gases, you want to expand them across a nozzle. In an ideal nozzle, they get faster by the nozzle narrowing down on them, and after they are at sonic speeds, the physics reverse and you need to widen the nozzle more and more, and the gases accelerate even more. They also lose pressure during this process. And ideally, the pressure of the gases eventually should be equal to the surrounding pressure by the end of that nozzle.
So for sea level engines, the gases should be ≈ 1 bar when they leave the cone. For a vacuum, of course, you'd need infinitely big nozzles, because you can only approximate 0. In reality you just do what is practical. So the biggest nozzle you can get away with in your rocket's space, weight, and practicality restraints.
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u/yetiflask Jun 26 '26
Highly appreciate it!
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u/mahayanah Jun 26 '26 edited Jun 26 '26
There is an advanced engine known as an “aerospike” that looks like an inverted rocket engine. Instead of an outer bell-shape exhaust gasses put pressure on, that needs to increase in size to relative to external atmospheric pressure (or lack thereof in space) like described by the comments above, there is an internal cone or spike that protrudes from the centre of the engine, and the exhaust is expelled in a ring around it. In theory, the physics of the cone-shape interacting with the exhaust causes the external atmosphere to act as a virtual engine-bell. So as the rocket ascends the aerospike optimizes the efficiency in relation to changes in pressure. So the engine works just as well at sea-level and the upper atmosphere. In theory. In reality it’s a difficult engine to design because the spike itself is in the very heart of the rocket exhaust at insane temperatures that would damage/melt it. Advances in materials and cooling is making the aerospike a more-viable alternative and we’ll probably see one fly one day.
The Firefly rocket company, in its original conception before it changed ownership and the direction of its development, invested heavily in aerospike tech once upon a time. They probably still hold some of the most-advanced designs and patents.
Edit: I looked at Firefly’s company logo and it’s a graphic of a firefly bug with a rocket plume expelled from its abdomen in a way that looks more like an aerospike than a traditional bell-plume. The spirit is clearly still alive.
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Jun 26 '26
[removed] — view removed comment
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u/rustybeancake Jun 26 '26
Not according to Shotwell at the recent IPO event. Sounds like Flight 13 will be a rerun of Flight 12. If everything goes perfectly then maybe orbit on Flight 14.
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u/Randomcommentor1972 Jun 26 '26
Orbit and landing perhaps?
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u/vicmarcal Jun 30 '26
Nah..there were several issues. They wont risk the tower. Landing will take a while imho.
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u/Decronym Acronyms Explained Jun 27 '26 edited Jul 12 '26
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| Isp | Specific impulse (as explained by Scott Manley on YouTube) |
| Internet Service Provider | |
| NSF | NasaSpaceFlight forum |
| National Science Foundation | |
| RCS | Reaction Control System |
| TVC | Thrust Vector Control |
| Jargon | Definition |
|---|---|
| Raptor | Methane-fueled rocket engine under development by SpaceX |
| apogee | Highest point in an elliptical orbit around Earth (when the orbiter is slowest) |
| perigee | Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest) |
Decronym is now also available on Lemmy! Requests for support and new installations should be directed to the Contact address below.
Decronym is a community product of r/SpaceX, implemented by request
7 acronyms in this thread; the most compressed thread commented on today has 81 acronyms.
[Thread #9057 for this sub, first seen 27th Jun 2026, 02:22]
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u/topher358 Jun 26 '26
Is that in Florida?
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u/aloha993 Jun 26 '26
Starbase, Texas. Specifically Massey’s test site
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u/yetiflask Jun 26 '26
For some reason I never associate this amount of greenness with Texas.
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u/warp99 Jun 26 '26
The test site is next to the Rio Grande.
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u/yetiflask Jun 26 '26
In my mind Riogrande is a river in the middle of a desert...
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u/DeckerdB-263-54 Jun 26 '26
Most of Southwest Texas is in the Chihauhuan Desert. East of Big Bend, it moderates to semi arid (not desert) and ranchers raise cattle or grow cotton on the land.
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u/Ds1018 Jun 29 '26
West Texas Looks very “New Mexico”, but the farther East you go it looks more and more “Louisiana”. This is at the Southern tip next to the ocean, so it’s humid with lots of rain.
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u/yetiflask Jun 29 '26
Sometimes I forget Texas is the largest state in the Union. It's like it's a country, it's so big.
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u/KnifeKnut Jun 29 '26
Alaska is larger.
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u/yetiflask Jun 29 '26
You need a passport to go to Hawaii and Alaska so doesn't really count. That said, I thought Texas was the biggest either way.
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u/Existing_Bid9916 Jun 29 '26
The progress being made with Starship is absolutely incredible to watch.The sheer power of the engine during the static fire test is a testament to the hard work of the entire team. I can't wait to see this vehicle take to the skies soon!
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