Sunday, March 20, 2022

Some Words About Last Night

I ended last night's post on SpaceX achieving yet another reuse record with a photo that caught a Falcon 9 seconds after lift off, while the booster from the mission a week before was being moved from the recovery drone onto the truck for transport to where it will be inspected and prepared for it's next flight.  I said, "in my mind, the way it ought to be."  This is not so much about the launch cadence of once a week, which is the only place in the world trying for that.  It's about the reuse of the hardware. 

I've only worked on the design of a few satellites, and really only one I can talk about by name and mission, back between about 1990 and 1996.  As a receiver and PLL synthesizer designer, I worked on those parts of satellites.  I believe the things I'm going to talk about apply to rockets and their hardware, both electronic and mechanical, but I never worked on a launch vehicle.  

Those who aren't familiar with the design world probably don't know this, but the price of the parts you buy depends on the conditions the parts are rated to work under.  The cheapest electronic parts are the plain commercial grade parts; they're rated for a narrow temperature range, from 0 to 50C, or 32 to 122F.  These are what are used in consumer devices of all kinds including inside the passenger compartments of cars.  There are three more stringent selection grades and each grade is more expensive than the one before: industrial (often -40 to +80C), Military (-55 to 125C) and then Space rated, or Class S.  There are others for really severe environments, but these are the main ranges.

Everyone who works on space hardware knows that the requirements always specify the most expensive parts made.  Class S parts are generally screened and tested to the same temperatures as military, unless there are requirements for that specific mission that go beyond those, and are also rated for their ability to survive radiation in space.  
 
It's important to say that there could be no difference between the silicon that makes up two parts, one commercial and one class S.  They can be made side by side on a wafer and one gets more tests and documentation than the other.  It's the difference in testing to guarantee the performance that raises the price.  That's why I think it's fair to lump things like engine turbopumps and processors; they're both the best parts because of the things done to guarantee they are.

To me, a very reasonable question goes something like "these are the best parts in the world and we throw them out after one use?"  We invoke these requirements to ensure that these very expensive satellites (or manned capsules), being lifted into orbit by even more expensive boosters, all perform their mission.  Most transistors or more complex circuits will run virtually forever, if you run them a bit below their absolute maximum ratings, but we throw these out after a few minutes of use?  Remember, Voyager has been running since 1977 - and those are probably 1973 vintage parts which ran for hundreds of hours in ground testing.   

We throw these out because "old space" never seriously asked the question of how much more work they would have to do in order to recover a booster, or how much capability they throw away on every mission.  They never really seriously contemplated "how can we do this?" because they never seriously thought there was a need to reuse boosters.  Congress was apparently happy to keep paying them whatever they billed for any launch vehicle - look no farther than SLS.  A week ago, I opined,
I've long thought that the way SpaceX developed the technology was brilliant.  I could see from the way ULA CEO Tory Bruno talked that he thought it would cost way too much money to develop and he just saw the costs entirely differently.  SpaceX seemed to think that they sent up a Falcon 9 for hire and when the booster separated, it had just been thrown out.  It's now "free" as if they picked it out of a trash pile to experiment on.  They can tell the engines to turn on for a very minimal amount of extra cost, and guide it to where it could land.  As long as the primary mission of launching a customer's satellite was accomplished, and every launch coverage has stressed that was their crucial part, everything after MECO was teaching them more than if they dropped the booster in the ocean.  True, the recovery drones were an expense and there were others, but those costs get amortized out over many recoveries - well over 100 at this time.
There's a Netflix documentary coming on the return of manned spaceflight to the US through SpaceX Crew Dragon and the story of getting there. There's a line in the trailer about how SpaceX changed the industry.  I would say they didn't simply change the industry; they changed everything.  The rest of the industry just hasn't learned that, yet.

Which raises the real question that if they can do 12 launches on one booster, how many more before it becomes too expensive to refurbish for reuse?  20?  Who knows?  Don Rumsfeld's quote about having known unknowns and unknown unknowns comes to mind. Last summer, Elon Musk was openly talking about boosters being launched 20 or 30 times, maybe up to 100 times, with periodic maintenance like commercial airliners get.  It's the dawn of a new age - the one promised to us 60 years ago.

B1051 after her 10th flight and arrival at Port Canaveral, two flights ago.  Richard Angle photo for Teslarati.

 

 

14 comments:

  1. Something that the reduced cost and increased launch tempo of the Falcon 9, and soon Starship, does is make recovering satellites and other orbital pieces-parts actually feasible.

    What was going to be a big part of the Shuttle program but never realized, the snagging of big, expensive satellites and returning them for refurb or salvaging and investigating what actually happens with long-term space exposure on equipment.

    So far only a few recovered satellites and the work on Hubble and the ISS have given engineers and scientists actual hands-on opportunities to actually investigate all the hazards of space, from radiation to huge temperature variations and, of course, space debris damage.

    Now? Just need a small 'tractor' or 'tug' to attach to a satellite or other orbital object to bring it into a recoverable orbit, and, of course, a way to grab, enclose, mount (maybe using airbags or something) and then deorbiting and returning to Earth.

    Or, wacky concept, set up an orbital repair facility (using, hmm, a Starship...)

    This, every/thing that was promised with post-lunar Apollo and never ever appeared, is possible with the low cost of launchers and returnable cargo space.

    No wonder legacy aerospace is using lawfare to slow-roll SpaceX.

    Thanks for the info on why space components are so darned expensive.

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  2. I'm guessing the largest concentration of strong structure on a satellite is where the last-stage engine attaches. So, put a mandrel made from a pipe surrounded by expanding gas bags up into the combustion chamber, already designed to retain thousands of psi in every direction, and hold it like a popsicle on a stick: Flexible Inflatable Satellite Tackle (tether, trail, trap, tool, trace). Who remembers Traveling Wave Amplifier Tube?

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    1. There is a company, forgotten which, that is developing precisely that.

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    2. I remember seeing a TWTA, which is rather different from remembering how they work.

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  3. At some point people will want to only hire "used" boosters because they know they work well.

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  4. A significant part of the cost of aerospace parts is the certification that they meet the requirements under which they were purchased. Structural items are supposedly tracked all the way back to the lot of the metal from which they were made. Of course, paying for that does not necessarily mean it was done. Lawrence Engineering bolts come to mind...

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    1. The running jokes used to be: "you're buying the paperwork, the parts themselves are free" and "before launch can be allowed, the paperwork stack has to be taller than the launch vehicle." Or it has to outweigh the launch vehicle.

      I'm sure there are more.



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  5. the most interesting part of your post is the mental aspect. the 5 minute mile barrier was a thing.. until it wasn't. I wonder what other self limiting paradigms mankind will break in the next 10 - 25 years as we start working the moon and mars habitability problem... if we don't nuke ourselves back to the middle ages

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  6. I think that one of the biggest concerns WRT reuse of the stages will be increasing metal fatigue. Mr. Musk is no doubt aware of this, and i presume that Space X is keeping close track of it, especially for critical components.
    It's been @20 years, but I worked on one of the ISS modules, and the lead engineer's biggest concern was over the increasing problem with metal fatigue.
    A good overview of the problem is given at Wikipedia:
    https://en.wikipedia.org/wiki/Corrosion_in_space
    I'm researching this subject in some depth, as I'm writing a hard SF novel on a different approach to getting to Earth orbit; JP Powell's Balloons to Space concept, and this is something that I'll have to address.

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    1. My guess, FWIW, is that the gotcha is going to be one of the unknown unknowns, to borrow Rumsfeld's quote. Metal fatigue is known, at least in the sense that everyone knows it exists, and probably addressed. What's going to get them is something out of the blue that wasn't considered.

      An advantage of stainless (as in Starship, not sure about F9) over aluminum is that if the loads are kept below some point, SS just elastically stretches and goes back to the original size.

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    2. Rumsfeld's remark was actually quite insightful. In 1995, i took a class in Denver on spacecraft design, and the instructor spent some time discussing unusual failure points on missiles, spacecraft and satellites. One unusual failure point occurred on a satellite that the instructor wouldn't name. Failure analysis over several weeks failed to find a cause, until an outside consultant went through the drawings and found something. There was a wire bundle that was not encased in protective sheathing. The bundle was routed through part of the structure, and had to be bent over an edge. No fillets or chamfers, just a straight, hard edge that during launch, laid bare at least a few of the wires. That led to an eventual fire and failure of the satellite.
      That has stuck with me for many years, and I've always insisted on either adding fillets or chamfers or wrapping the bundles in protective sheathing. Both is better, by far.
      I have been favorably impressed with SpaceX's QC operations, having worked a stint as a design checker for one of their vendors some years back.
      I'm hoping to read the headline in about 10 years that one of their first stages has reached the 100 flights mark, and that Mr. Musk is going to shoot for 1000.

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    3. Maybe I'm stupidly optimistic, but as many times as a sharp edge has bitten into wires like that, I would hope it would never get past PDR or the earliest design discussions. Design rules just wouldn't allow it and just wouldn't get as far as actually flying.

      Back a couple of months ago, the small startup company Astra tried a launch from Cape Canaveral SFS. The fairing failed to detach properly and the mission failed. When they did the post mortem, they found it was one of those cases where the documentation was backwards, but the people doing the wiring faithfully and accurately followed it, and they were followed by the Quality Assurance group ensuring it was properly built to documents. That kind of thing happens All The Time.

      It's why my concern about AI isn't that it's gonna go all Skynet on us to kill us off, or that's it's gonna go all "Three Laws of Robotics" and enslave us to protect us. It's that some software is gonna have a minor error that completely changes the meaning and kill us all off doing what it "thought" was good.

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  7. Something that puzzles me, and I have not seen addressed in any of the discussions, is the Falcon 9 second stages. Are they discarded to burn up on reentry, and where does all that debris end up? As this post discusses, that's a lot of hardware to be discarding--once a week now! It must be quite an assembly line producing them. I realize that the Falcon 9 is seen as an interim vehicle until Starship/Booster is fully operational. At this time though, Falcon 9 and Soyuz are the only options for manned missions to LEO. Or am I missing something here entirely?

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    1. Yes, the second stages reenter and burn up within a day or two, depending on the mission. It is a lot of hardware to be disposing of, and it's not all in one place. They work to get them to end up in the oceans, but that's about all.

      There was talk about trying to recover them like the booster and fairings, but I haven't heard anything about that in a while; maybe a couple of years.

      The production line must be pretty busy, and they need to do some boosters now and then so that they remember how.

      Other than Falcon 9 and Soyuz, I know of no other manned vehicles to LEO. Boeing's capsule had a disastrous test flight, and getting it ready to re-test has been one problem after another. Last I heard the next test flight is no earlier than this May.

      The next Crew Dragon manned flight is the 30th and will be a 100% private mission for a company called Axiom. Their focus is getting a private space station built.

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