RedKraken

<wild-ass speculation> Within 2 years, we will know if full-reuse in steel is going to work (re-entry). Allow for quite a few fails (crashes, reentry damage) here. Pad1. Booster1. Another 4 or 5 years of bedding in cargo SS like F9. Allow for a couple of mission fails (and 3 or 4 block improvements). Refueling sorted out. Pad2. Booster2. GTO rideshares (carousel + 12t kickstages) for short-term cash. Dozens of LEO missions for starlink long-term cash. Tanker version starship. Within 8 years, prestige missions to moon/mars....unmanned first, later crewed. Starlink half complete. Pad3. Booster3. First P2P cargo routes within 10 years. Short range (2000km) with just suborbital starship config.. Long Range with suborbital stack. Offshore pads. 12m prototype. Starlink complete w/ 2nd and 3rd gen sats. Another 10 years to go for P2P cargo to go from exclusive to common. </WAS>

That really is good news.

Probably both, eventually. <wild-ass speculation> assuming 200t, 330s-356s, 25MPa, 1.3m engine : They need 3 tested engines for hopper, 7 for starship, and a dozen initially for SH (31 all up), plus a few spares. I think they will be building close to 50 engines over the next 12 months. IIRC a merlin 1D takes about 30 hrs to make, and costs them about 500k USD. (M1D Vac is about x8 time and cost.) I don't know how raptor will compare to that. They might aim to build one a week at cost 2-3 million each. I expect they will pull a few apart. They might run destructive tests to find pressure/temp limits. They will need to run 180-200s for booster engines, 300-400s (full tank) for the starship to orbit and maybe another 300-400s (full tank) for any missions to moon/mars. Another 300-400s (half-tank) to come back from mars. Landings add another 30-40s. So an individual mars engine might end up burning 100%throttle for a total of ~1200 seconds, and consume 0.600x1200 = 720 tonnes of propellant before it gets home for a service. The remaining engines will do maybe half that. We might see engine mods after this series of stand tests, after the hopper tests, and after Starship1 does its test regime. </speculation>

My first (and very half-assed) meme :

Congrats Elon and spx crew. I thought you had popped an engine for sure.

Agreed.... I wonder how things would have turned out if the flight team walked out to scrub a shuttle launch. Career-ending at the time?.... i would prefer to be known as the guys that walked out over safety and lost their jobs. SpaceX operations - anyone on the flight team can scrub a mission? Some folks are very dangerous to be around. Maintain a safe distance and an exit strategy.

Not so much about bashing yourself.... more about anticipating problems....checking assumptions....preparing for uncertainty....planning....covering weak spots.....doing experiments for situations where data is sparse or non-existent.... testing your margins.... checking your simulations against telemetry. Looking at some spacex failures can be instructive. https://en.wikipedia.org/wiki/History_of_SpaceX#Setbacks strut failure crs-7 : do you trust your vendors QC? no way....check your assumptions...test your input materials with more rigour..automate testing. copv failure amos-6: new fueling regime uncovered a structural weakness....testing on the pad is a bad idea....esp with a customer payload. Blow up a test pad. Thats what its for. landing failures : out of teta/teab for a valuable FH core.... this one hurts...its a planning failure. The stuck grid-fin on CRS-16 mission was very interesting. A graceful fail into the ocean. But can u imagine the BFB doing this?

Elon's commenting that being smart does not save you from doing dumb things. Certain learning environments are less forgiving than others. I like tater's comment about hiring smart folks....surround yourself with excellence. Learn what they know..... practice like they practice. The self-awareness of the limits of your abilities. Situational awareness of whats going on around you. The mindset of relentless self-improvers.

An interesting tweet from elon : How many space engineering disasters have we seen caused by smartness over-reach? For example : Apollo 1 capsule fire. Nedelin/Plesetsk pad disasters. n1 program. shuttle program. Mayelin village. Ariane 5 self-destruct. How do you combat dangerous feelings of smartness in the engineering space?

from alhenry1231 at NSF, chonk, thic, smol. https://forum.nasaspaceflight.com/index.php?PHPSESSID=3mnvqm2u62b0p33hn43ev5oqo0&amp;topic=41363.1540 Some folks think that raptors size has suddenly changed. I don't think so. You still have to fit 31 of these under 9m tanks....even with a 10m skirt.

The change to steel got BFR moving fast. And looks like a much stronger, simpler and cheaper design. Transpiration cooling for reentry looks promising...but represents most of the project risk. We have a junkyard hopper built in about 10 weeks. Flying soon. And a BFS prototype being built in parallel, due this year. We have new raptors on the test stands. Now we have booster design simplified from cradle to BFS style landing legs. And cold gas thrusters ??? wait! what? Elon is really pushing hard. This is the best show on the planet right now.

Holy moley.....250t .sl. optimised for the next version... sad BE-4 face. Anyone want to have a guess at the ER and isp? That pic with the human for scale is awesome. The powerhead has an interesting footprint....tall and skinny for the booster i guess. I wonder what the mass ended up .... 1000 kg?

Very interesting! Here is some design goals, volumes, mass estimates and extra diagrams for the craft : http://www.astronautix.com/a/apollomartin410.html

Mr steven of the future has methane thrusters for directional control. Is a hovercraft for catch mode. Lift fans are methane-electric (diesel-electric analog) Then converts to ekranoplane-mode for distance travel. It doesn't have a net at all... just a tub for the fairing to slot into. Not serious .... unless it works.

Yes. Not enough savings to justify new line. The cost savings might look like 2-3 million on 8 (out of 24) launches per year. ~20 million savings per year....just isnt enough. Starman3408 nailed it. I would be interested to know what a steel equivalent of the composite fairing would weigh (guess 300%?), and how much quicker (easier) it could be produced. It may not be useful for spacex. But other agencies might be interested.

I'm thinking you are right.... I had not considered this.

I don't think it could be structural stress. The fairing can be as strong (and heavy) as you need.... even a 20t fairing wouldn't put a big dent in the small payload performance. Although after 25t i expect you would have to start reenforce the stages like FH...or redesign from scratch...not worth it. You could be right about the teams/personnel. Starship has all of the priority now.

I feel a bit flat.....like the hopper fairing. https://twitter.com/RogerLewisHolt/status/1088211714863218688

Why does SpaceX use expensive fairings for small payloads ? I'm talking about any GTO mission around 3 tonnes or less. Or any LEO mission at all since the adaptor is rated about 10 tonnes, when the vehicle is capable of 23-24 tonnes. Falc9 has so much margin on these missions. Why use a super-light, expensive, 6 month lead-time fairing when you could use a very cheap, expendable steel fairing? I must be missing something important. Some fairing info : https://www.reddit.com/r/spacex/comments/7llf74/anatomy_of_a_falcon_9_fairing/ The current composite fairing weighs in at about 2 tonnes. Steel is about 5 times the density of composite (8000 kg/m3 versus 1600) A cheap 10 tonne fairing in steel would penalise less than 10% of its payload (GTO or LEO) on small payload missions. And you could throw it away without incurring a significant loss. (Doesn't work for larger payloads because the deltav margins are too fine.) The booster does all of the hard work, and does not care if it is lifting 550t or 560t off the pad. The upper stage is 115t (normal fairing) or 123t(proposed heavy fairing), but only carries the fairing for 30 seconds in a 300 second burn. I'm sure spacex must have looked at cheap, heavy fairings but decided against them. What is the reason?

If your oxidiser tank is 261 m^3, your CH4 only needs to be ((261/0.54) - 261) = 222 m^3 to get 3.6 O/F ratio. Sev is using 3.8, not really a big difference in this case. (Volume ratio for 3.6 is roughly 54% lox, 46% CH4.) 483 m^3 total bulk methalox subcooled is ~ 900kg per m^3 so 483 * 0.9 = 435t On the other hand, if the methane tank is 261 m^3, your oxidiser should be (261/0.46 - 261) = 306 m^3 567 m^3 total so 567 * 0.9 = 510t I'm going to use a much lighter hopper mass (given the fairing blew over, doh) than sev. Based on 3.5mm average thickness SS, rather than the 5mm i was using before. Fairing will be much less thick. Base will be much more. I read somewhere NSF? in the last day that tank pres (3atm?) will require about 3.5mm for the starship tanks. Hopper could get away with less. I'm starting to think it will be around 40t. 510 t prop, 40t dry , 330s is about 8500 m/s deltaV. Thats a lot of dv.....flying low will average slightly above 330s isp too.

I think hopper will work fine. No big unknowns here, and a lot of lower level risk retired (engines, autogen press, rcs thrusters). Starship hops will be awesome, but i expect most problems to crop up (drag fin actuators and suborbital reentry testing, landing practice). Some top level risk retired here. Booster hop test? Should not throw any problems if hopper tests are successful.. Starship (from booster) should get to orbit fine. Booster rtls (cradle away from pad) should be fine. More risk retired. First orbital reentry attempt...might throw up some unusual results..or outlier parameters. Or just explode. I hope not. The next 3 years are going to be intense, even if stuff comes in late. Aside from dragon2, FH, hopper, SSH and SS : We get Ariane 6 due next year. Vulcan and New Glenn due 2021. SLS will stagger ahead like a crippled brontosaur. Whatever the chinese, russians and indians decide to work on. Methalox and steel. 2020 Mars mission and James webb 2021. Might see vector get to orbit. Might see electric pumps and methane in small rocket format. So much going on, makes me want to go back to school to skill-up.

Here are some numbers for the re-entry cooling energy budget : from this thread : https://www.reddit.com/r/spacex/comments/a9y9r0/an_energy_budget_for_starship_reentry/ The entry speed they were using : 8km/s (so LEO reentry, not mars(12km/s?) or lunar (11km/s?)) Mass : 110t Kinetic Energy = 3500 GJ (LEO re-entry)...... Heat energy reaching the craft = ~ 1% or 35GJ for the cooling system to deal with. This is the key number here and i'm not sure how accurate or precise it is. I'm a thermodynamics rookie, so i have to rely on other folks to refine it. The other critical number is the transpiration cooling : 3GJ of cooling per tonne of methane.... high?, low? about right? The spacecraft itself might end up sinking 5, 10 or 20GJ? for a couple of minutes before it starts to cool in the lower atmosphere. I will be keen to see if Elon gives us some actual numbers.

https://www.popularmechanics.com/space/rockets/a25953663/elon-musk-spacex-bfr-stainless-steel/ Yes. Very easy to work with steel. Oh, and I forgot to mention: The carbon fiber is $135 a kilogram, 35 percent scrap, so you’re starting to approach almost $200 a kilogram. The steel is $3 a kilogram. It’s just 301 stainless. With steel, now you’ve got something where you can comfortably be at a 1500 F interface temperature instead of, say, a 300 F, so you have five times the temperature capability at interface point. What that means is that for a steel structure, the leeward side of the back shell does not need any heat shielding. On the windward side, what I want to do is have the first-ever regenerative heat shield. A double-walled stainless shell—like a stainless-steel sandwich, essentially, with two layers. You just need, essentially, two layers that are joined with stringers. You flow either fuel or water in between the sandwich layer, and then you have micro-perforations on the outside—very tiny perforations—and you essentially bleed water, or you could bleed fuel, through the micro-perforations on the outside. You wouldn’t see them unless you got up close. But you use transpiration cooling to cool the windward side of the rocket. So the whole thing will still look fully chrome, like this cocktail shaker in front of us. But one side will be double-walled and that serves a double purpose, which is to stiffen the structure of the vehicle so it does not suffer from the fate of the Atlas. You have a heat shield that serves double duty as structure. https://www.reddit.com/r/spacex/comments/ain1kk/elon_musk_why_im_building_the_starship_out_of/

Nice shot of the RL-10 deploying its extendable bell.

NROL-71 at vandy, 2min to launch.