Wiki Super Heavy/Starship - General Development Discussion

[Ben W]

At the risk of stating the overtly obvious, it’s worth noting that electric propulsion requires a massive amount of DC power to charge the field and huck molecules out the business end. The good news is that it’s a very compatible concept with communications satellites (most GEOs, most megaconstellations, etc) as they already have large power subsystems to supply the power hungry payloads….but for a mission that doesn’t otherwise need a ton of power (imaging sats, a fuel depot, etc) it can result in an EPS materially bigger than is otherwise necessary.

In the case of putting EP on Booster that would mean a massive solar array, batteries, chargers, etc. All totally doable for sure...its just going to be on an unprecedented scale. For reference, PPE--which near as I know is the largest contemplated EP system to-date--has something like a 50kW power subsystem and is going to push around 40T worth of mass. An EP Booster will be probably mass an order of magnitude or more higher.

From the internet engineering perspective Its also worth throwing in here that EP tanks are really high pressure--MEOP is in the 400+ bar range and the load is in the 300's. So...they kinda need their own tanks. In the contemplated re-use concept the pressurant tanks would likely suffice, though volume would likely be an issue.

And finally, just for funsies, its worth noting that both the Xenon and Krypton markets have been MASSIVELY impacted by Vlad's antics, since much of the world's supply--especially Xe--comes from the Ukraine. The price has gone up like 6-10x since he decided to wage not-war, and its super fluctuatey and generally difficult to procure. Plenty of folks are scrambling to develop alternatives but its not easy because the efficiency of Xe is hard to beat--that's why it was chosen in the first place for EP. Krypton is above Xe on the table and so its lower molecular mass makes it that much less efficient. Iodine is probably going to emerge as the winner (Busek is already advertising it) as its pretty heavy (its right next to Xenon on the table) and also can be stored as a solid so the reduction in storage vessels brings a lot of volume/mass upside there.

This is super informative. Thanks!

I sort of pictured that the krypton/xenon would be cryogenically liquefied in the tanks, rather than stored as a high pressure gas. They have similar boiling points as methalox. (I suggested krypton because it's 10x cheaper than xenon, Vlad notwithstanding, though still admittedly very pricey.) The high pressure would mostly come for free as the propellant converts itself from liquid to gas. For big missions, an RTG or very small nuclear reactor (think nuclear submarine but smaller) might work for providing constant power for electric ion propulsion, if not VASIMR directly. Iodine may get around some of these issues, as it's cheaper (10x again cheaper than krypton), and doesn't need to be cryogenically cooled, though I don't see how the methalox tanks could be repurposed for it. Just thinking out loud, and I am admittedly not an expert on this!

 

[HVM]

https://twitter.com/x/status/1571929797185667072

 

[HVM]

https://twitter.com/x/status/1571935414448963586

Booster 7 now returns to high bay for robustness upgrades & booster 8 moves to pad for testing. Next big test is probably full stack wet dress rehearsal, then 33 engine firing in a few weeks.

 

[ecarfan]

Very interesting! If B7 is going to be upgraded, I interpret that to mean that the plan is still to send it to orbit first. SpaceX will take advantage of the vacated OLM to test B8 so that it can be launched as soon as possible after B7. But which ship will be paired with B8? I assume S25 as it has been fully stacked but it was rolled to the high bay for stacking without any TPS tiles in place.

Another ship nosecone has been moved out of the tent and to the windbreak bay but it also has no tiles in place, and interestingly, no flap mounts. Maybe it is destined to be the nose for the first Depot Starship?

 

[Electroman]

https://twitter.com/x/status/1571935414448963586

I am a bit nervous on how things will hold up when all 33 are firing with NO flame trench. Don't have a good feeling on that.

 

[mongo]

I am a bit nervous on how things will hold up when all 33 are firing with NO flame trench. Don't have a good feeling on that.

The whole under-stand is a flame trench, what's missing is a diverter.
Unlike STS, the entire bottom of the booster is engines pushing out an insane amount of exhaust at high speed. Also a different type than solid boosters. The staggered startup with the center three first startup may induce outward flow that helps direct the remaining engine's exhaust.

Interesting to see what deluge system ends up looking like.

 

[ecarfan]

Another ship nosecone has been moved out of the tent and to the windbreak bay but it also has no tiles in place, and interestingly, no flap mounts. Maybe it is destined to be the nose for the first Depot Starship?

New video from NSF discussing the different Starship variants mentions that that nosecone with no tiles or flap attachment points could be for a Depot Starship, go to the 8 minute point in the video. Or it could be for Starlink V2 or other missions where the ship would be expended.

 

[bxr140]

Iodine may get around some of these issues, as it's cheaper (10x again cheaper than krypton), and doesn't need to be cryogenically cooled, though I don't see how the methalox tanks could be repurposed for it. Just thinking out loud, and I am admittedly not an expert on this!

Cryo is generally avoided for long term space use--it’s pretty finnicky versus to pressure vessels. Its actually going to be pretty interesting to see how SpaceX solves that problem when it comes to starship refueling anf long term storage. Yeah, space is cold...but if you're not careful space is hot too...

Anyway, I guess the EP topic also really depends on the problem that's being solved. It feels like anything that moves humans needs to be raptor driven, given the timelines involved with super low thrust EP (the "big" thrusters on PPE are I think around 1N). And anything that lands on a surface (the moon, mars) also needs to be Raptor-ed, so obviously neither of those would use EP...so I think what we're really talking about here with EP is 1) a proper methalox depot--either in earth orbit or transported beyond earth--and then maybe also 2) some non-human cargo transport.

From the fuel depot perspective obviously the tanks can't be repurposed, but that's ok in the iodine scenario since storing as a solid is a huge volume advantage. There's a gazillion ways to conops that kind of depot solution; generally I think some EP pack that's integrated on the Depot Booster (either on the ground or once on orbit…in either case maybe at the pointy end...?) probably does the job. And even with pressurized Krypton tanks there's a huge ∆V-per-volume (and mass) upside versus combustibles that probably still works out.

For the non-human EP cargo transport I think First Principals drives that to a less constrained form factor than something that needs to land and take off on planets. If its too big to stuff into a Starship you just send up modules on a couple starships and assemble it on orbit.

 

[mongo]

So much new info on Twitter

• Booster 7 getting reliability upgrades
• Booters 9 (in process) has many design changes, especially for isolating engine RUD
• (Sub) orbital test late October or, more likely, November
• Will have two full stacks ready in November and a production rate of one full stack every two months
• Can transport ships from Brownsville to Cape
• 39-A launch around Q2 2023 with TX built stack

https://twitter.com/x/status/1572568337263243264

 

[ecarfan]

And B8 has now been rolled out to the pad area in preparation for placing it on the OLM (after B7 is removed) and doing cryo tests.

 

[ecarfan]

See Post #365 at NSF for a summary by @RingWatchers of what is happening with the S26 nosecone, which has no TPMS, no flap mounts, and other unusual features. Possibly it will be for a Starship that will be used for the first on orbit cryogenic propellant transfer test, which SpaceX has a NASA contract for.

 

[ecarfan]

New photo of the Starlink “PEZ dispenser” assembly being installed into the payload section of what is believed to be S27.

https://twitter.com/x/status/1572599428913008640

 

[Electroman]

This is how they are going to dispense the Starlink satellites?

The design of Starship without fairings will make it challenging to deploy multiple satellites of various sizes. They all need to be dispensed in one direction and through one outlet.

 

[Ben W]

Cryo is generally avoided for long term space use--it’s pretty finnicky versus to pressure vessels. Its actually going to be pretty interesting to see how SpaceX solves that problem when it comes to starship refueling anf long term storage. Yeah, space is cold...but if you're not careful space is hot too...

Anyway, I guess the EP topic also really depends on the problem that's being solved. It feels like anything that moves humans needs to be raptor driven, given the timelines involved with super low thrust EP (the "big" thrusters on PPE are I think around 1N). And anything that lands on a surface (the moon, mars) also needs to be Raptor-ed, so obviously neither of those would use EP...so I think what we're really talking about here with EP is 1) a proper methalox depot--either in earth orbit or transported beyond earth--and then maybe also 2) some non-human cargo transport.

From the fuel depot perspective obviously the tanks can't be repurposed, but that's ok in the iodine scenario since storing as a solid is a huge volume advantage. There's a gazillion ways to conops that kind of depot solution; generally I think some EP pack that's integrated on the Depot Booster (either on the ground or once on orbit…in either case maybe at the pointy end...?) probably does the job. And even with pressurized Krypton tanks there's a huge ∆V-per-volume (and mass) upside versus combustibles that probably still works out.

For the non-human EP cargo transport I think First Principals drives that to a less constrained form factor than something that needs to land and take off on planets. If its too big to stuff into a Starship you just send up modules on a couple starships and assemble it on orbit.

JWST seems to have figured out the cooling side of things pretty well. Agreed that limited EP thrust would probably restrict its use to non-crewed missions, unless it were used as e.g. an interplanetary cycler a la "The Martian". A very large ion engine (or several in parallel) might give 10N of thrust, compared to 2 million Newtons for a single Raptor. So a one-minute Raptor burn would be equivalent to about a five-month 10N ion burn.

I was more thinking about crazy science missions like putting a telescope at 50x the distance of Pluto, at which distance the sun becomes a gravitational lens. Fun to think about how the Starship platform might enable things like this!

 

[ICUDoc]

one-minute Raptor burn would be equivalent to about a five-month 10N ion burn

Wow, that's a crazy comparison!

 

[ecarfan]

This is how they are going to dispense the Starlink satellites?

The design of Starship without fairings will make it challenging to deploy multiple satellites of various sizes. They all need to be dispensed in one direction and through one outlet.

That is how SpaceX plans to deploy Starlink V2 sats using Starship.

That is not how SpaceX will design a Starship to deploy other types of satellites for commercial and government customers. See https://www.spacex.com/vehicles/starship/

 

[mongo]

Not super scientific, but in this slow motion of the 7 engine static fire, it can be observed that the condensation clouds are not showing signs of being buffeted by reflected engine exhaust.

 

[ecarfan]

Thanks for posting that. Beautiful video. Not sure if I could detect all 7 engines starts but saw at least 5.

No sign of a water deluge system in operation.

 

[ecarfan]

No sign of a water deluge system in operation.

And now there is.

https://twitter.com/x/status/1572945869783322625

https://twitter.com/x/status/1572945108722675712

@mlindner at NSF posted:

This is a sound suppression system. They're using high pressure nitrogen to atomize the water to increase surface area in the air. They're doing this instead of a traditional deluge system because they're not allowed by environmental rules to discharge water into the surroundings without some kind of catchment pond, which they don't want to wait to have to build (because permission would take time and have to undergo state engineering review). Sound suppression works by basically making the air "heavier" such that it absorbs sound as compared to the surrounding air.

 

[Electroman]

But why 6 minutes? By the 6th minute the first stage would be on its way back after staging. Perhaps needed for 30 seconds maybe?