totm nov 2023 SpaceX Discussion Thread

[tater]

Another thing... he earlier tweeted that Mks1/2 are ~200 tons. They are similar construction, welded from many small panels. All the rings in FL are the single seam type, and are for Mk4. Mk3 will start in TX soon, also the single seam type I think, unless he said Mks4/5 would be the lighter ones, in which case Mk3 might be some other method. Regardless, that's a LOT of Starships. What for?

Presumably they expect to break some would be my guess.

 

 

Click the second image to enlarge it, and check out the legs...

Looks like with a small payload, and starting from an elliptical orbit, a refilled SS could do a lunar surface RT. Where "small" is 20-30 tons.

They could deliver an entire Artemis lander to Gateway. Oh, and bring the Gateway at the same time.

[Xd the great]

21 minutes ago, tater said:

They could deliver an entire Artemis lander to Gateway. Oh, and bring the Gateway at the same time.

NASA: slowly develops SLS, attempts to bring Gateway one piece at a time to Halo orbit

Musk: Boom look at my big shiny stick. Also, it can bring the entire gateway to the Moon at once.

[kerbiloid]

50 minutes ago, tater said:

One thing that is clearly different on the current prototypes vs the renders: The belly.

On the renders, what are bulges for landing legs on the current vehicle have a flat area between them on the renders.

Dorsal side here:

Good, good, the heat-protected belly.

Quote

Ep1. "Teflon (donkey)". Starship receives heat protection from one ("bottom") side. ('cuz why fry only nose when you can glide and dissipate the heat with bottom?) (hi, full-steel last-winter Starship!).

U R here.

[RealKerbal3x]

Since it was at 1AM for me, I wasn't able to watch it live, but I've seen the replay now.

Not much new for someone who's been religiously following progress, but at least we got to see some cool renders. I have to say, this new design is really growing on me.

[MinimumSky5]

Ars did an interview with Musk after the press event, and they expanded on a couple of points:

https://arstechnica.com/features/2019/09/after-starship-unveiling-mars-seems-a-little-closer/

The big one for me is that SpaceX has learnt a lot about life support from working on Crew Dragon, and Elon is at least dimly aware that a full regenerative system is needed for Mars transfers.

[Wjolcz]

I have to say that Tim Dodd has grown on me. He asks far better questions than other journalists.

Though I still consider his overreacting and twitter spam a bit cringey.

[ChrisSpace]

7 hours ago, Spaceception said:

Yeah. To be honest, I'm really hoping sooner rather than later, SpaceX finds problems with life support, and go off to develop specialized systems (and we get a proper presentation for it). Like what food will be grown on Mars, and how will it be grown? How much energy and mass will the food/air/water/waste systems require? How are habitats going to be built? How will you protect people from radiation? What will the spacesuits look like? How are you going to maintain and repair the interiors/spacesuits/filters of martian dust? I just want to know how SpaceX themselves will address these.

While there have already been a few research studies about these topics and how SpaceX could approach them (most notably the "Project Destiny" concept from 2017), I think SpaceX will be a bit unique in whatever solutions they come up with. In the concept art we can already see a dome with something green inside it, probably trees, and just outside we can see multiple rows of solar panels, so that already gives a hint as to what they're planning to do for life support and energy systems.

6 hours ago, insert_name said:

Think of the ISS as a research ship and BFR as a ferry, I am expecting that the 100 figure is for the point to point version. Also ISS crew size is limited by the vehicles flying to it, not the volume

I think 100 could be doable for flights to the moon as well, since that's only half a week. As for Mars, well remember that the "100" number was originally made during the ITS era when SpaceX was planning to use a 12m spaceship instead of a 9m one. On a trip to Mars, I'd put 100 as an absolute upper limit and 12 as an absolute lower limit. In 2017 or 2018 they mentioned putting 40 cabins in a 9m BFR, and that seems like a good number.

Also, between the recent presentation/twitter pics and the ITS renders from 2016, and the Methane-based chemical propulsion used by the Starship system, I'm starting to suspect that SpaceX is already eyeing the Saturn system, specifically Titan, as the next main target after the moon and Mars. I'm probably jumping to conclusions a little early but it would make sense.

[MinimumSky5]

How long would it take for Starship to get to Saturn? AFAIK, it would be multiple years. 

[ThatGuyWithALongUsername]

Just now, MinimumSky5 said:

How long would it take for Starship to get to Saturn? AFAIK, it would be multiple years. 

Not quite as long if you launch and refuel *from Mars.*

 

Elon has talked about setting up fuel depots everywhere once, so that makes it sound like the outer solar system missions might not launch from Earth, but rather have supplies sent to Mars, refueled, and launched from there with crew missions also launching from Mars. IDK though, and I don't  think it actually shortens the trip that much, but it could help, especially if you refuel in Mars orbit.

 

He also mentioned destinations past Mars to be Ceres, Callisto, Ganymede and Titan, all of which, fairly particularly it seems, have water ice and carbon dioxide or carbon something. So maybe it could even launch from Jupiter or something.

[Xd the great]

Just now, ThatGuyWithALongUsername said:

He also mentioned destinations past Mars to be Ceres, Callisto, Ganymede and Titan, all of which, fairly particularly it seems, have water ice and carbon dioxide or carbon something. So maybe it could even launch from Jupiter or something.

Now this is pod racing making life multiplanetary.

[kerbiloid]

Now he is trying to launch a flight demonstrator with more than one engine, lol.

[AVaughan]

9 hours ago, cubinator said:

You could do 100 people if every one of them is perfectly fine with never being alone.

With a pressurised volume of 1000 cubic metres you could give everyone a personal "cabin" of 1.5m x 1.5m x 2.25m = 5.0625 cubic metres (5 foot x 5 foot x 7.5 foot) and only use about 50% of that volume.  Not a lot of space for a private cabin, but enough to sit/lie down/sleep/stretch/read/watch tv or a laptop plus store some personal possessions etc. 

I'm not sure whether the remaining 50% of pressurised volume would be enough for life support, food storage, and communal areas like kitchen/dining areas, bathrooms and exercise equipment though.  (Although presumably not everyone will do everything simultaneously, so they don't need a 100 person dining room or gym).

[RealKerbal3x]

1 minute ago, AVaughan said:

I'm not sure whether the remaining 50% of pressurised volume would be enough for life support, food storage, and communal areas like kitchen/dining areas, bathrooms and exercise equipment though.  (Although presumably not everyone will do everything simultaneously, so they don't need a 100 person dining room or gym).

They could sleep and eat in shifts, so that 50 people sleep while the other 50 are awake.

[kerbiloid]

14 minutes ago, AVaughan said:

With a pressurised volume of 1000 cubic metres you could give everyone a personal "cabin" of 1.5m x 1.5m x 2.25m = 5.0625 cubic metres (5 foot x 5 foot x 7.5 foot) and only use about 50% of that volume.  Not a lot of space for a private cabin, but enough to sit/lie down/sleep/stretch/read/watch tv or a laptop plus store some personal possessions etc. 

28 m³/human is required for long-lasting space missions. (Studies from 1960s-70s).
In orbital stations typically 20..80 m³ depending on circumstances.

Edited September 29, 2019 by kerbiloid

[AVaughan]

I'm slightly surprised that the vacuum Raptors won't gimbal.  If everything is working properly, that isn't an issue.  They can use either differential throttle and/or rcs for steering during burns, assuming all three engines are operating.  But if a vacuum raptor were to fail that would only work if the vacuum Raptors are aligned through the centre of mass, and not parallel to the hull.  Aligning them through the centre of mass would mean a tiny cosine loss (probably negligible overall; it might even be smaller than the dV gained from the weight savings from a lighter engine that doesn't gimbal) but would also mean that they couldn't use differential throttle to steer, and would have to rely to rcs.

 

6 minutes ago, kerbiloid said:

28 m³/human is required for long-lasting space missions. (Studies from 1960s-70s).

Source?  Also were those studies for 6-8 month trips, or for 2-3 year trips?

[cubinator]

9 hours ago, Spaceception said:

... what food will be grown on Mars, and how will it be grown? How much energy and mass will the food/air/water/waste systems require?

*cough crickets cough*

I am going to do a study on this - the feed mass required over a two-year trip, how long it takes to produce a serving in a self-contained unit of, say, one cubic meter, whether current methods of feeding and cleaning would be feasible in 0-g...We know they're a good choice for food, but who's ever actually built a box and farmed them in the context of spaceflight?

[kerbiloid]

16 minutes ago, AVaughan said:

Source?  Also were those studies for 6-8 month trips, or for 2-3 year trips?

1. A paper book "Problems of space biology and medicine", in Russian.
2. A ESA Martian expedition project (can be found in pdf, several times linked here).

Both say "27" and "28" m³/human. The former - for "multiday expedition" or so, the latter is a calculation of a Martian ship.

35 minutes ago, AVaughan said:

(Although presumably not everyone will do everything simultaneously, so they don't need a 100 person dining room or gym).

Though, 100 persons require 20..30 toilet seats each with pipes and pumps.
(Probably can be used for methane ISRU, too, lol.)

Upd.
http://emits.sso.esa.int/emits-doc/1-5200-RD20-HMM_Technical_Report_Final_Version.pdf
but looks like they're currently down.

Upd 2.
Idea for the next Musk/Zubrin project: a toroidal vacuum toilet with places for 20 persons at once.
Let the toilet shifts be named "platoons".

Edited September 29, 2019 by kerbiloid

[RealKerbal3x]

I don't think anyone has posted this particular render here yet, so here you go:

I have to say, I really like the look of this design. It still looks 50s sci-fi without the danger of the actuating control surfaces also acting as landing gear.

[kerbiloid]

7 minutes ago, RealKerbal3x said:

It still looks 50s sci-fi without the danger of the actuating control surfaces also acting as landing gear.

Just wait a little either for the first one overturned with pax onboard, or for wheel gears instead of legs and larger wings then.

Edited September 29, 2019 by kerbiloid

[Rakaydos]

6 minutes ago, kerbiloid said:

Just wait a little either for the first one overturned with pax onboard, or for wheel gears instead of legs and larger wings then.

Wings? what wings? There's no wings on that craft, because it never leaves aerodynamic stall.

[sevenperforce]

6 hours ago, tater said:

6 hours ago, mikegarrison said:

One thing I didn't know was that they are going with ceramic tiles as their heat shield. Shuttle, anyone?

Yeah, that was interesting, though they tested some on the last cargo Dragon, and they attached some to Hopper (presumably for vibration, acoustics, etc).

I can understand that the substrate (steel) can take higher temps, but you have to wonder about any adhesive used, strikes me that would perhaps be the limiting factor. That said, X-37 has some thinner ceramic tiles as I understand it.

The ceramic/glass tiles will be bolted on, not glued on as with the Shuttle. As you know, the primary concern for the Shuttle tiles was foam strikes, because of the idiotic choice to sling the orbiter alongside a giant tank covered in icy flaky insulation rather than putting the crew vehicle on top where it belonged. But the adhesive was also problematic, and it was something like two man-years of work just for tile maintenance between each flight. Adhesive failure (caused during early flights because engineers would spit in the glue to make it easier to work with) resulted in multiple tile loss every flight. Not all the tiles were different shapes, but most were.

Not only will Starship lack any problems with foam strikes, but it will also take fewer, larger tiles that are almost all approximately the same size. Because they will be bolted on, rather than glued, it will be easier to replace and inspect. As shown by this image of the way they were affixed on Starhopper, they will simply be affixed by transplanar bolts:

Spoiler

Presumably the bolts will run to nuts welded onto Starship's outer skin. THAT will be a lot of work. By pixel counting, each of those tiles is roughly 31.5 cm across horizontally, or 863 cm². A 50-meter-high, 9-meter-wide vehicle has a cross-section on one side of 834 square meters, not counting the Plasma Deflector Shields or Squid Fins. Let's round up to 1000 square meters to account for those control surfaces. So we're looking at roughly 11,600 tiles. Maintenance on 11,600 identical bolted-on tiles should be easier than the Shuttle's 21,000 varying-geometry glued-on tiles. Welding on the 35,000 nuts will be a pain for sure, though.

My guess is that the size of the tiles is as large as they can get while still ensuring that the loss of any single tile will not be catastrophic. It's particularly significant that bolting the tiles on will make it impossible to have a "zipper" failure, which was always a dramatic concern for the Shuttle.

7 hours ago, tater said:

One thing that is clearly different on the current prototypes vs the renders: The belly.

On the renders, what are bulges for landing legs on the current vehicle have a flat area between them on the renders.

I suspect they are still iterating leg design. The current legs on Mk1 are simply steel I-beams enclosed inside those little tack-welded fairings; they're definitely not retractable or extendable. We may see them swap these out for this version before it flies, or we may see them jack it up and add crush cores underneath and then fly.

Elon definitely made it seem like the chances of Mk1 or Mk2 ever going to orbit are very low, so I wouldn't expect to ever see thermal tiles coating this particular vehicle, although the "belly band" may be a place where we see them test the tile attachments. Landing legs will likely be identical on both windward and leeward for Mk1 and Mk2. With Mk3 and Mk4, which will have full heat shields, we'll see a different shape on the windward side to minimize sharp edges. 

They may go with fixed-column legs on the windward side (as shown in current renders) and fold-down or push-out legs to leeward, just to give a little extra stability. 

It was interesting that Elon said he wanted to try and skip the entry burn for Superheavy, as planned for New Glenn. With 301 stainless it should be easier to buff up the base. I don't know what I think about those legs, though.

[sevenperforce]

2 minutes ago, Rakaydos said:

Wings? what wings? There's no wings on that craft, because it never leaves aerodynamic stall.

I would say that if we're being technical, the control surfaces never leave aerodynamic stall. The body stays in a hypersonic lift state for most of entry, right up until the final "drop" from 20 km or so. But of course your point is right.

18 minutes ago, RealKerbal3x said:

I have to say, I really like the look of this design. It still looks 50s sci-fi without the danger of the actuating control surfaces also acting as landing gear.

I am surprised they have not yet gone to a cargo-bay approach, keeping the header tanks and other stuff in the nose as with the current model and doing a cylindrical payload section, including for the manned version.

The hot-gas thrusters are pretty cool, though. I wonder -- if they put the meth and ox bottles up front, would the hot-gas thrusters be strong enough (and oriented properly) to provide abort capability for the crew cabin?

One thing he didn't discuss in connection to the hot-gas thrusters is that the meth and ox bottles can be refueled with a simple pump from tap-off of the tank pressurant or from thermal vaporization of main-tank props. They seem to have wholly abandoned transpiration cooling plans, but I wonder if they might revisit a regenerative cooling approach. Weld piping along the stagnation path of the hypersonic flow and pipe cryo methane and LOX through to vaporize and thus sap heat. You need to vaporize props to keep the hot-gas thruster bottles full, after all. 

With similar channels on the leeward side, you could even use this system in space for power generation on orbit. Pipe liquid methane through the sunward side to vaporize and run a generator; pipe the methane gas through the leeward side to condense. Solar power without solar panels.

[ThatGuyWithALongUsername]

2 minutes ago, sevenperforce said:

*long informative post*

*like*

 

Also, with the higher melting point of steel and the multiple bolts, it's entirely possible that even if a tile does get cracked in flight, it would stay bolted on and the stainless steel could take the heat.

 

Also, willing to bet that there's some work being done towards making the inspection quicker- maybe even to the point of using fancy equipment to just do a "quick scan" of the entire heat shield, instead of manually inspecting every single tile up close, but I really, really don't know enough about how that might work- I'm just imagining that with all our computery advances since the 1980's, surely that could help speed it up somehow.

 

Also, some questions: Where are the header tanks? There's a window at the nosecone, but they aren't in the tanks?

And are the grid fins on the booster still made of solid cast Titanium? Because that's a lot of Titanium.

[sevenperforce]

1 hour ago, AVaughan said:

I'm slightly surprised that the vacuum Raptors won't gimbal.  If everything is working properly, that isn't an issue.  They can use either differential throttle and/or rcs for steering during burns, assuming all three engines are operating.  But if a vacuum raptor were to fail that would only work if the vacuum Raptors are aligned through the centre of mass, and not parallel to the hull.  Aligning them through the centre of mass would mean a tiny cosine loss (probably negligible overall; it might even be smaller than the dV gained from the weight savings from a lighter engine that doesn't gimbal) but would also mean that they couldn't use differential throttle to steer, and would have to rely to rcs.

I think they just don't have space for them to gimbal. If there was a vacuum Raptor failure, I think they'd just use the SL engines instead. SL Raptors have such a high chamber pressure that underexpansion losses aren't too bad. 

Ideally, you'd want a single gimballing vacuum Raptor in the center, so you could perform single-engine vacuum burns as efficiently as possible. The engines on the outside would be the SL raptors and they could gimbal in through the CoM or in parallel. But they didn't really have space for that, and putting the SL cluster at the center also allows for up to a double-engine-out landing, where the SL Raptor gimbals through the CoM alone and can still touch down safely. 

[tater]

1 hour ago, kerbiloid said:

28 m³/human is required for long-lasting space missions. (Studies from 1960s-70s).
In orbital stations typically 20..80 m³ depending on circumstances.

Seems pretty reasonable to me. the 100 people on one of these things for a long time seems absurd. It basically has a volume similar to my house, maybe 200 m³ smaller than my house, actually. We have 100+ people in the house for parties, and it's not all that bad, but I wouldn't want to live that way for years. The above numbers you quote would be 35 people in Starship. For years. Even that is pretty high, but way more sensible than 100.

24 minutes ago, sevenperforce said:

It was interesting that Elon said he wanted to try and skip the entry burn for Superheavy, as planned for New Glenn. With 301 stainless it should be easier to buff up the base. I don't know what I think about those legs, though.

The narrow stance freaks me out, frankly.

@mikegarrison said the best thing up this thread. It was the F-86 to Mig-15 comparison. It is now a meme to me, it's what I think when I see the vehicle standing in TX. I think, as they go first to the single weld rings, the ship will get cleaner, and cleaner, and will in fact evolve to be far more like the F-86 in that comparison. These early few vehicles 2 per facility) are throw aways for testing.

Edited September 29, 2019 by tater