For those who aren't following this religiously like I am, here's the Tl;Dw:
SpaceX's falcon 9 is pretty big, but Starship is massively larger. It's also made cheaply out of steel in a huge garage in rural Texas. The engines are the most advanced ever made (arguably). Tomorrow, SpaceX is going to try to fly the prototype 12.5km up, then have it freefall, falling sideways. At the last moment, it will reorient itself and land on a landing pad.
Just to add a bit more color on size: Starship itself is about 50m in height, somewhat shorter than the full Falcon 9 stack (70m). Starship has a much larger diameter though, at 9m vs 3.7m for Falcon9.
But Starship is just the second stage. That's what's being tested tomorrow.
Eventually this will sit atop a massive new super-heavy booster. The full stack will be 122m high, nearly 2.5x taller than Falcon 9, and with a dramatically larger volume.
That might be a better definition of science than “It’s like messing around, but taking notes.”
I love how everyone quotes it, and SpaceX deserves the credit for making that attitude popular. But what really makes it possible is cheap cameras — so when watching a blast that is likely destroying every living thing and destroying every piece of electronic in its way, I’ll be cheering for GoPro too.
I think the increased telemetry ("3000 channels" per the Falcon 9 AMOS-6 explosion; who knows what Starship will have) and the ease nowadays with which one could store the data on an SD card tucked inside every multiply-redundant avionics box, makes it much more likely you'll be able to pinpoint the cause of an error even after a catastrophic explosion. Hence enabling SpaceX to fail-fast with confidence that they will be able to find the problem from the data and fix it.
Plus apparently they're relatively cheap to build, that just makes the test even cheaper.
They at least used SD cards in GoPro cameras on fairings. I admit I cannot authoritatively speak to what they are using for telemetry storage if they decided to go that way.
SD card connections are unreliable in an environment with heavy vibrations (something you’d expect with a rocket). For something like a GoPro, that might be acceptable to SpaceX, but for critical telemetry data, I highly doubt it as GP stated.
Also important to note that this is Starship Serial Number 8. If it has an "accident" it's good to know that there is actually a Starship SN9 that has just been completed at the manufacturing base a couple km from the launch site, standing by to take its place and try again.
Then there are two more vehicles abou 50% done - just join the tanks and add the pointy part in the front.
And parts have been spotted assigned up to SN16!
So this is really no ordinary space program where you prepare for years to launch a single super expensive rocket and then deliberate for months or years what went wrong and how to fix it.
No, they built the best rocket engine ever, attach it to glamurous 50s SF rocket built from stainless steel (and random Falcon 9/Dragon/Tesla parts) in a marsh and then launch and make more until it can go to space cheaply and reliably.
> The engines are the most advanced ever made (arguably).
Maybe not arguably. They embody a technology that's been considered for a long time the Holy Grail of rocket science - the full-flow staged combustion cycle:
As much as I love the Space Shuttle, I wish the US had not went all in on Hydrogen Oxygen. The RS-25 are amazing engines, but we could have had operational full flow staged engines 20 years ago if we had gone down that route. Though probably not the landing part.
Interesting that full flow LOX-LH2 engines could be easier to get, as oxygen and hydrogen can be ignited in a wide range of ratio. With LOX-kero you might have to have a two stage gas generator, when first you ignite components with a good ratio and then add a component to the already established combustion.
If you were wanting to optimize for high specific impulse, it seems LOX-LH2:Be or a fluorine based fuel is the way to go purely on the numbers (not accounting for cost or stability).
TL;DR: Liquid-fuel rockets work by combining a liquid fuel with oxygen. To get the fuel and oxygen into the combustion chamber in huge quantities, they use a big fancy pump. To power this big fancy pump, all liquid-fuel rockets burn fuel in a separate combustion chamber, using the hot gas to power the pump. After the gas powers the pump, it has to go somewhere. Most rockets just dump the gas (these are called 'Gas-generator cycle' engines). This is nice and easy (ha), but it also means that the gas isn't going through the main combustion chamber, so it isn't propelling the rocket. The rockets on Starship re-use the gas that drives the pumps, pushing them into the combustion chamber and burning any unused fuel/oxygen to propel the rocket.
Fascinating! Their rocket's trust-weight ratio (~73, according to Wiki) is WAY below the state of the art gas-generator cycle Merlin (~185), presumably because of the added weight of the motor and batteries required to operate an electric turbopump. It's always interesting to see folks look past a supposedly bad design and discover that its other benefits (in this case, cost and simplified design, apparently?) can still render it a viable option.
> The rockets on Starship re-use the gas that drives the pumps, pushing them into the combustion chamber
How is that possible? From a total layman's point of view, the pressure in the combustion chamber should always be greater than whatever the pump can put out, thus leading to a pump stall... what am I missing?
Actually the pump has to be able to put out as much if not more pressure than the pressure generated in the combustion chamber, otherwise it wouldn't be able to push a steady stream of fuel and oxidizer into the chamber.
Okay, I'll bite, How many moving parts do the SpaceX engines have?
Assuming the fuel and oxidizer impellers are on a common shaft, that's one. There must be a throttle valve somewhere, so that's two. What am I missing? Are there reduction gears?
Yes, indeed, we have plenty of real-life cyberpunk around us already, may it please be the time when earlier space SF finally starts to become real, too? :)
>Tomorrow, SpaceX is going to try to fly the prototype 12.5km up, then have it freefall, falling sideways. At the last moment, it will reorient itself and land on a landing pad.
The model is pretty current (except for the tank strapped on the side that is downwind during the drop phase) and the flight phases look reasonable as well (phases: launch, horizontal drop with flaps correcting the position and a turn to land vertically again).
I’ve been following testing progress on /r/spacex and it’s a lot of fun having such a detailed view into the whole operation as these Starship prototypes are built and iterated upon out in the open.
Elon has said chance of a soft landing is less than 50%, so I would expect a very eventful livestream. Personally I’m hoping to see re-light and some sort of flip, with limited damage to ground support equipment. IMO a soft landing is too much to even hope for.
The engine re-light is non-trivial because they will be fed from a separate header tank at the tip of the nosecone at that point.
It would not be surprising if this didn’t actually happen tomorrow, there’s a million things which could lead to further delays. If it happens at all this month it would be thrilling.
They actually lost the center booster, so not entirely nailed. Unfortunately we didn't get good imagery of that particular catastrophe, but if Starship goes down in flames it will be within reach of lots of ground-based cameras. Would make for pretty fireworks.
In case people don't know, they hit the orbit they were going for.
This was a solar orbit that goes out as far as Mars orbit, but does not actually rendezvous with Mars. It's similar to the first part of a Hohmann transfer, but without course correction and circularisation burns.
Trying to actually hit Mars would require launching within a specific window, as well as all the other things required for planetary missions - powered upper stage (not a car), planetary protection protocols, etc.
So actually hitting Mars would not only restrict launch opportunities (bad for a test launch) but would also add a whole suite of costs associated with going to another planet (also bad for a test).
I don't think they ever actually tried to hit mars. mars was in completely the wrong orbit at time of launch - they just wanted to get to about where mars would have been.
Doing the landing swing move and then stopping the swing with the rocket engine seems dicey to me. The timing on those firings need to be incredibly accurate.
The next prototype is already built, so if this one lands nose first they can just fix any issues and try again. Elon really is building rockets like a software engineer.
There a free app that lets you fly the Starship made by Austin Meyer [0]. I highly recommend anyone with an iOS device who is interested to give it a try.
Youtuber Everyday Astronaut is on South Padre this week getting ready to live stream the festivities. I recommend all good space nerds have it on on the background tomorrow.
There are daily videos of the construction and test site, by Mary @BocaChicaGal and NASASpaceFlight. Pretty marsh sunrises over rockets, and meditative construction timelapses. Today's: https://www.youtube.com/watch?v=cRN2Ikt6x6w
Stainless maintains better strength at ultra low temperatures, is an order of magnitude cheaper, and can be manufactured more easily with a vastly larger set of forming and joining options.
But, that doesn't explain why he never mentions titanium, which is the other half of the question. If you even mention aluminum, the titanium question is clearly more relevant.
And, if these things are to be re-used, up-front material cost is less relevant than value. Titanium maybe doesn't get stronger at cryo temperatures, but is it still stronger than steel at such a temperatures? I couldn't find numbers. If it is, the dry weight of the vehicle could be much less, with large follow-on benefits.
Stainless strength is ~1600MPA at -200C, Titanium is ~900MPA. Density difference is 8.0g/cc vs. 4.5g/cc for titanium. So at low temp, strength to weight ratio is about even.
Maximum working temp for stainless is ~800C vs ~600C for Titanium, therefore requiring a smaller heat shield. Some parts of the vehicle will require no shielding or insulation.
So strength to weight is a wash at low temp (fully loaded with propellant), stainless is better at high temp (re-entry) and Titanium costs ~10x more. Aluminum is also cheap and easy to work with but will require larger heat shields. SpaceX is making a trade-off between weight, re-usability, development cost, and development speed. I really think between the marginal performance benefits and significant manufacturability challenges Titanium just doesn't bring a lot to the table.
Somebody said Ti was 10x as expensive, but numbers I see are closer to 2x, which surprised me. Ti is supposed to be radically less subject to fatigue cracking, so ought to last longer and need less inspection, but is harder to get good welds in, in the first place.
I guess they can build them both ways, for different use cases, in time.
SpaceX's falcon 9 is pretty big, but Starship is massively larger. It's also made cheaply out of steel in a huge garage in rural Texas. The engines are the most advanced ever made (arguably). Tomorrow, SpaceX is going to try to fly the prototype 12.5km up, then have it freefall, falling sideways. At the last moment, it will reorient itself and land on a landing pad.
Or, it will explode stupendously.
It's going to be awesome either way.