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If you take the time to study the documentation from the 1950s & 1960s, the engineering culture of that era appears to be markedly different from the engineerin
by areoform 2y ago
If you take the time to study the documentation from the 1950s & 1960s, the engineering culture of that era appears to be markedly different from the engineering culture prevalent today. And I think it's deeply rooted in the symbiotic relationship between computing, Baumol's cost disease and our obsession with precision, results-oriented, MBA-style-min-maxing, "good enough for government work" engineering.
Robert Truax, the designer of the Sea Dragon, loved to promote the design paradigm of Big Dumb Boosters. Instead of many small, sophisticated rocket engines, what if we made one big robust one that can take a lickin' and keep on kickin'.
The idea was to relax the mass margins and to create big. dumb. boosters. It's the approach TRW explicitly followed for the Lunar Module engine,
> "There was an amusing but instructive side to this program. TRW farmed-out the fabrication of the engine and its supporting structure, less the injector that they fabricated themselves, to a "job-shop" commercial steel fabricator located near their facility . The contract price was $ 8000. Two TRW executives visited the facility to observe the fabrication process. They found only one individual working on the hardware, and when queried, he did not know nor care that he was building an aerospace rocket engine."
> " I had arrived late to witness the test, and only saw the firing. I was told by others who witnessed the entire test procedure that the engine was pulled out of outdoor storage where it lay unprotected against the elements. Before it was placed on the launch stand, the test crew dusted off the desert sand that had clung to it. This unplanned inlcusion [sic] of a bit of an environmental test also demonstrated hardware ruggedness of the kind no other liquid rocket eingine [sic] could approach."
The Surveyor program managed to make it "just work" 5 out of 7 times by adopting this approach. It had robust landing legs and RADAR. They would decelerate and then shut off the engine 11' above the surface. The wide, sturdy legs would then absorb that final impact of coming stand still from free fall.
These programs had a lot of capital behind them. Some components required precision engineering, but there's a very clear through line and embrace of the "we gotta make stuff that can take a lickin' & keeps kickin'" philosophy.
Modern engineering approaches seem to be the opposite of that. I think we've become so accustomed to living in a silicon driven world where our personal devices are engineered at microscopic level that we've forgotten how to do things the Apollo-era way.
For example, to the best of my knowledge, IM-2 doesn't use RADAR — they're using LIDAR and optical navigation instead. Perhaps it is to save on mass and power so that more payload reaches the surface. Perhaps optical navigation was declared to be "good enough." Perhaps it doesn't make sense from a minmaxing of capital perspective. But this philosophy may not be suited to an untamed frontier.
China adopted the Surveyor / Apollo-era philosophy. Their first successful lander, Chang'e 3, used the same hover & fall technique as Surveyor.
> The vehicle will hover at this altitude, moving horizontally under its own guidance to avoid obstacles, and then slowly descend to 4 m above the ground, at which point its engine will shut down for a free-fall onto the lunar surface. The landing site will be at Sinus Iridum, at a latitude of 44º.
It chose the terminal landing sites with the help of LIDAR and its cameras, but it relied on RADAR and a suite of sensors to have robust navigation.
The follow up missions up-ed the ante every time, but they seem to have consistently focused on the robustness of their craft over precision, MBA-spreadsheet-oriented minmax-ing.
- dylan604 2y ago> Perhaps it is to save on mass and power so that more payload reaches the surface. It doesn't matter how much mass was saved and how much more payload that allowed to reach the surface if the landing isn't successful. Successful landing is mandatory for anything else to matter. The obviousness of this baffles me that it is taken so haphazardly.
- ordu 2y agoI believe that the thing you are missing is Intuitive Machines aims at landing a lot of spacecrafts, not just one. They hope to have a limited number of failures to land which will teach them how to do it reliably. We might doubt will this work or not, but if we accept the plan then it becomes a rational decision to increase the engineering complexity and risks of failure by saving on mass, because in the long run less missions will allow to land more payload. Though, of course, I wonder how many landings they are planning to do, and how many of them they need to do to compensate for each failure to land.
- dylan604 2y agoAgain, if you can't stick the landing, you might as well not have any payload on it. So if you're worried about cost, keep testing until you can stick the landing with dummy mass. Once that works, send the real payload. Otherwise, you're just wasting payload. The mindset difference seems to be that if there's no human on board, so no problemo wasting a lander if something goes wrong. That's just a bad attitude (as well as yaw and roll). If you designed everything with "baby on board" hanging in the window, you'd probably not cut so many corners so sharply. Otherwise, why not just light your cigars with hundred dollar bills. How would you feel if you were on the team building the payload, but the lander guys keep fucking up so you just wasted however much time you spent because "meh, we're just testing". In sports, there's a saying "practice like you play because you play like you practice".
- cratermoon 2y agoOkay but successfully landing an inanimate carbon rod is easy, but why?