[ExI] spacex landing on boat

[spike at rainier66.com]

…> On Behalf Of Dan TheBookMan via extropy-chat

Subject: Re: [ExI] spacex landing on boat

 

On Dec 31, 2020, at 2:32 PM, spike jones via extropy-chat <extropy-chat at lists.extropy.org <mailto:extropy-chat at lists.extropy.org> > wrote:

I share this Twitter user’s attitude about how cool this is, but disagree with his comment on impossible.  It was generally agreed by about the late 1990s that it is possible to land a rocket feet first.

 

https://twitter.com/i/status/1343959265988411394

 

spike

 

>…I think his statement — ‘Still kinda hard to believe this was considered *impossible* 5 years ago’ — is vague enough to border on being meaningless. He doesn’t say by whom and even when you say ‘generally’ it’s unstated who you mean. I gather you mean by experts in the field and not, say, the general public or even educated members of the general public…

 

Ja, not by 5 yrs ago.  By then the consensus of the people in the biz I think would have been the feet first landing is possible.  There were credible papers being presented in that direction as much as 30 yrs ago by guys who understood control loops, structural dynamics, performance of thrust vector control, all the elements.  

 

I might be flattering myself here (but hey, somebody hasta do it) and I am watching for my own confirmation bias.  But I give a lotta credit to the big advances made in fiber optic angular accelerometers.  I thought that whole concept was just wicked cool first time I heard of it, and they were returning astonishing numbers: their speed in feeding back info to central processors in the control loop was mind-blowing, and they were handing it accurate numbers.  Working on that gyro accelerometer was one of the most exciting projects I ever did.

 

The structural dynamics modeling advanced some, materials not so much really (we were using good old 6061 alloy for nearly everything the whole time) the actuator tech advanced some.  But it was the calculation end of it, getting the signals from the accelerometers enough times per second, deciding what to do and getting it done before the booster had time to get squirrelly, that was what got this done.  I looked over the control models and thought around 2000 or 2001 that someone would manage the feet first lander.  I didn’t know it was only 15 yrs off.  I mighta guessed at least 20.

 

 

 

>…By the way, I was thinking of how back before SpaceX accomplished this I thought it was very high risk…

 

You were right: it was a crazy high risk project.  Those landings are still high risk: I wouldn’t be surprised if they lose a rocket about every 10 flights.

 

>… Am I wee too cautious or was SpaceX just lucky? Dan

 

 

I am willing to credit the guys at SpaceX.  Their controls guys are just on it.  I bet they enjoy going to the conferences these days: the ordinary controls proles would surely treat them with a lotta respect.

 

I had an idea: go see if I could get a job at SpaceX trimming the hedges or cleaning the restrooms, get a SpaceX badge, go to the controls conferences, act like a bigshot, then when the SpaceX guys don’t know who I am, act like it’s so secret I don’t even know what I am doing.

 

spike

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