News:




  • May 22, 2018, 07:55:14 AM

Login with username, password and session length

Author Topic: Space man in a Tesla -is the AC on?  (Read 1727 times)

Offline Paul Taylor

  • Moderator
  • Trade Count: (0)
  • Admiral
  • *****
  • Posts: 5514
  • If God is your Co-pilot - swap seats!
    • Our Local CL Web Page
Space man in a Tesla -is the AC on?
« on: February 13, 2018, 11:04:20 AM »
Ok I know we have a few rocket scientists here. 
I read something the other day on the Falcon launch.
We all saw it go up and the boosters return. Cool stuff.

And some folks are still not sure we put a man on the moon and the earth is flat. I'm not in that crowd.

I got to witness a Shuttle flight so I know we can achieve space flight.

But what got me thinking was what I read about temperatures of space. Temps go from +250F in the sunlight down to -250F in the shadows. Eloin said they did not harden the roadster for space. But I would assume that the tires had no air in them.
So the questions about why the interior of the car is not melted or maybe paint popping off.
Just something to ponder.... 🤔
Paul

AMA 842917


Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #1 on: February 13, 2018, 11:31:52 AM »
But what got me thinking was what I read about temperatures of space. Temps go from +250F in the sunlight down to -250F in the shadows. Eloin said they did not harden the roadster for space. But I would assume that the tires had no air in them.
So the questions about why the interior of the car is not melted or maybe paint popping off.
Just something to ponder.... 🤔

      On the topic of the tires, the gauge pressure only went up by 15 PSI, so if they started with 20-25 PSI, it would stay within the max pressure rating of around 40 (which itself has tremendous margin built in - I see people in autocross running close to 60 psi at times, and I have never seen a tire fail due to overpressure).

     The "+250/-250" range is sort of a misleading measurement. Just like anything else, it depends on material and the thermal conductivity of the parts, the mass and heat capacity, how well they are attached thermally. A block of bare aluminum conducts heat from one side to another well that it goes to a constant moderate temperature as the heat coming in from one side conducts across and radiates out the other - to the best possible background most of the time (-470-ish degrees F, a few Rankines above absolute zero). They were in a rather rapid thermal-control rotation, maybe 1 deg/second, and thats fast enough to take full advantage of the thermal mass taking long enough to heat up on one side and cool down on the other. The only items that are unusual compared to a spacecraft are the carbon parts, those are probably getting pretty hot depending the duty cycle of the sun, so I did sort of expect those to start to blister/outgas/reach the glass transition temperature, and maybe they did. Since there was no load on it, hard to say how strong it remained.

     Things tend to get hot, for the most part, more than cold, because the thermal input is about the same as it is on the ground, but the processes of convection and conduction do not exist. The universe acts like a thermos bottle. The only mitigating factor is the fact that instead of having a nice warm 70-degree background to radiate into, you have the aforementioned 2-5 Rankine black body to radiate into, or at least, half the radiating space is like that (the other half being the 70ish degree earth, and the reflected radiation from the Earth albedo - which is quite significant to the problem).

     So, I would guess that you wouldn't want to put your bare finger on the carbon hood insert, but the metal parts are probably pretty reasonable, and if anything gets "up sun" for long it gets pretty warm but not absurd, and the "down sun" side might be pretty frosty, but still not absurd. The danger spots would be organic/plastic and leather/low-conductivity parts that happen to also have the sun and a reflection of the sun, and stay in one orientation for a long time.

    Brett

Offline Fredvon4

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1488
  • Central Texas
Re: Space man in a Tesla -is the AC on?
« Reply #2 on: February 13, 2018, 11:53:20 AM »
Based on my computer building when we Over clocked CPUs by a huge percent and NEEDED perfect as possible heat sinks... I had to learn a lot about  thermodynamics....

I (with a meager education) actually could understand Brett's response...

Just as a side note.... I imported a black on black with black leather interior  (tee top glass) sports car from Germany to Virginia in the 80s
Got moved to Texas and it sat out in 105F uncovered parking lot all day long.... put a oven thermometer inside to find 280F interior temps

did not hurt the car ----butt my butt  roasted for long times waiting on AC to get me down to a reasonable 77F

MY current ride has cooled seats... and remote start----life is good
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Paul Taylor

  • Moderator
  • Trade Count: (0)
  • Admiral
  • *****
  • Posts: 5514
  • If God is your Co-pilot - swap seats!
    • Our Local CL Web Page
Re: Space man in a Tesla -is the AC on?
« Reply #3 on: February 13, 2018, 01:17:41 PM »
Ok I think I understand - but now my brain hurts. LOL.

I don't have to ponder any longer. 😎

Thanks guys.
Paul

AMA 842917

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3834
  • Millville NJ PDQ Flying Clown Country
Re: Space man in a Tesla -is the AC on?
« Reply #4 on: February 13, 2018, 06:03:33 PM »
I'm still laughin' about that. There's a car up there with an F'n space man in it LOL! LL~
There will be a sunny day and we will fly our airplanes.

Offline Bill Adair

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 783
  • AMA 182626
Re: Space man in a Tesla -is the AC on?
« Reply #5 on: February 13, 2018, 07:28:22 PM »
I'd be interest in how they prepared the Tesla for that journey?

For example, removed the tire valves, drained all liquids, and renewed the license tabs for as long as allowed!  ;D

Bill
Flying control line again, after a forty-nine year break!

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 263
Re: Space man in a Tesla -is the AC on?
« Reply #6 on: February 13, 2018, 09:16:30 PM »
That is impressive and I am glad that the United States has launch vehicles again but I missed something about putting a car in space. Tim
Baton Rouge Bi-Liners
AMA 179681

Offline Peter Nevai

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 832
    • DasNet Corporation
Re: Space man in a Tesla -is the AC on?
« Reply #7 on: February 13, 2018, 09:32:55 PM »
I would gather that radiation exposure will show effects on the tesla long before the temperature extremes. UV, Gamma, Xray radiation unfiltered by an atmosphere will take it's toll. Organics like plastics, rubber etc. will take the heaviest hits. I gather it will be glowing in the dark before too long.
Words Spoken by the first human to set foot on Mars... "Now What?"

Online Chris McMillin

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1693
  • AMA 32529
Re: Space man in a Tesla -is the AC on?
« Reply #8 on: February 13, 2018, 11:35:14 PM »
Brett,
Did they leave the battery out do you think?
Chris...

Offline Jim Carter

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 550
Re: Space man in a Tesla -is the AC on?
« Reply #9 on: February 14, 2018, 07:18:07 AM »
 %^@ %^@  Our national and international/global efforts to launch to space and study the cosmos is an absolutely magnificent and wonderful thing, I agree wholeheartedly  ;).  The missions to the Moon, Saturn, the Asteroids and now, into interstellar space thanks to Voyager are quite simply mind boggling to me  ::).  I think the thing that worries me is:  "IF" .... there is an advanced alien life .... what happens if they will get pissed and send this stuff back with a note saying .... QUIT LITTERING OR ELSE!!  LL~ LL~

Offline Phil Krankowski

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 995
Re: Space man in a Tesla -is the AC on?
« Reply #10 on: February 14, 2018, 09:15:08 AM »
Part fun, part publicity stunt, part "science"...

Yea he could have boosted a block of concrete, and would still have the same "littering" problem, but it wouldn't have been different from any other heavy test launch.

Someone could have solicited part of the risk for a cheap boost too, but nobody was apparently interested, or prepared.

Boost a full success, 2 of 3 boosters landed safe, with the third crashing on landing.  Pretty good really.

Phil

Offline Lauri Malila

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1061
Re: Space man in a Tesla -is the AC on?
« Reply #11 on: February 14, 2018, 06:39:34 PM »
Did the 3rd really crash? I thought it landed in a sameway to a landing pad in sea, a few hundred km from the launchpad. It failed to land properly? L

Offline Phil Krankowski

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 995
Re: Space man in a Tesla -is the AC on?
« Reply #12 on: February 14, 2018, 07:43:20 PM »
https://www.space.com/39690-elon-musk-explains-falcon-heavy-core-booster-crash.html

Yes, at sea.  Quite literally ran out of fuel.

The twin boosters landed with absurd choreography.   Simultaneously, like a launch in reverse.  The video is really cool.

But there is no video of the crash, that I am aware of.

Phil

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #13 on: February 14, 2018, 09:59:44 PM »
https://www.space.com/39690-elon-musk-explains-falcon-heavy-core-booster-crash.html

Yes, at sea.  Quite literally ran out of fuel.

The twin boosters landed with absurd choreography.   Simultaneously, like a launch in reverse. 

      That's more-or-less how it functions, too. Only three of the nine booster engines operate for landing, since it's so light by then, but otherwise, it probably uses the same or very similar control system as boost. As anyone who has played "Lander" for any time, you find quickly that you want to run at idle and let it drop more-or-less free until the last possible moment, then go to full thrust to the point the velocity and altitude get to zero at the same time.

   The center booster didn't run out of fuel, it ran out of start fluid. The engines use TEB (triethyl borane) injected into the engine to cause them to start. This is great stuff, drip it on the carpet, the carpet bursts into flame, drip it on aluminum, the aluminum bursts into flame, drip it on your arm, your skin bursts into flame, that sort of thing. It's dangerous stuff to have around. It was also implicated in the ground explosion they had a few years ago.  They used the same thing to get the engines on the A-12/SR-71 to start, since the fuel is so insensitive to temperature (being used as engine coolant before being injected).

     Anyway, they ran out of TEB so two of the three engines failed to start, and it went submarining at about 300 mph and missed the target boat by about 100 yards (which is fine since it would have probably sunk the thing). You could see the slosh from the crash on the video, right before the splash destroyed the video feed somehow.

    Brett

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #14 on: February 14, 2018, 10:07:43 PM »
Brett,
Did they leave the battery out do you think?
Chris...

   Probably, but bear in mind it would be a LI-ION battery/batteries since it's a Tesla, not a conventional car battery. Also no radiator fluid, oil, etc.  Probably the brake fluid - which wouldn't be that much of a problem but would sort of "creep" out of the cap. It wouldn't boil.  The air in the tires would be OK, no need to take that out. The wax sprayed into the chassis for rust prevention (this was a Lotus Elise to start with) would probably be fine too.

    So probably very little preparation, as long as you don't care what happens a week down the road - which they don't because it's hundreds of thousands of miles away at this point.

     Brett

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #15 on: February 14, 2018, 10:26:07 PM »
I stayed close during the whole launch window so as not to miss any of it. It was as refreshing and exciting as the first launch of the Columbia shuttle to see us back into the serious business of space travel. I haven't missed many televised launches since Mercury.

The next day I scoured YouTube for more information and perspectives and that turned into a bad idea. All sorts of self appointed experts with nothing more than degrees from the "U. of 'Tube" were angrily shouting it all down as fake. Fairly sickening. But one of them did catch something that I couldn't help but wonder about. He was pointing out how the two camera feeds on the side boosters' plumes were identical. Every motion and the size and shapes of the exhaust plumes, flares, and reflections were identical second by second during the ascent. Like one camera was split to make both feeds.

Then on Thursday in the SpaceX launch video, it had changed and the exhaust plumes were obviously different. I can think up several possible explanations, but there was no notice attached regarding it having been edited.

I'm not really worried about it. I have no doubts, especially as so many people were there to see it launch and land, but I'd rather not have started watching the haters' videos flooding the place.
Rusty - Space Junky from way back.
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #16 on: February 15, 2018, 01:47:29 PM »
The next day I scoured YouTube for more information and perspectives and that turned into a bad idea. All sorts of self appointed experts with nothing more than degrees from the "U. of 'Tube" were angrily shouting it all down as fake. Fairly sickening. But one of them did catch something that I couldn't help but wonder about. He was pointing out how the two camera feeds on the side boosters' plumes were identical. Every motion and the size and shapes of the exhaust plumes, flares, and reflections were identical second by second during the ascent. Like one camera was split to make both feeds.

    That was probably a copy-paste error. When they went to build the display, they wrote the HMTL for putting (say) the "right-hand" window on the display, then to put up the "left-hand" display, they copied the first one, pasted it in for the second, changed the position attribute to move it to the other side of the window, but failed to select which camera feed to use, so it was the same one. Later, they fixed it and remade the movie.

   There's no reason at all to believe it was faked, their system appears to be perfectly consistent with the claimed performance, and plenty of people saw the plume from the TMI burn from the ground with the naked eye. If nothing else, they probably wouldn't have tthought to include FOD/ice floating away from the booster that you could clearly see in the video in a CGI system. You could check the shape of the clouds on the Earth in the video, and compare them to the same time and place from an independent weather site. You can put in "real" cloud densities into a CGI movie easily enough, but not live, as far as I know.

    Brett

Offline Peter Nevai

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 832
    • DasNet Corporation
Re: Space man in a Tesla -is the AC on?
« Reply #17 on: February 15, 2018, 09:18:12 PM »
I stayed close during the whole launch window so as not to miss any of it. It was as refreshing and exciting as the first launch of the Columbia shuttle to see us back into the serious business of space travel. I haven't missed many televised launches since Mercury.

The next day I scoured YouTube for more information and perspectives and that turned into a bad idea. All sorts of self appointed experts with nothing more than degrees from the "U. of 'Tube" were angrily shouting it all down as fake. Fairly sickening. But one of them did catch something that I couldn't help but wonder about. He was pointing out how the two camera feeds on the side boosters' plumes were identical. Every motion and the size and shapes of the exhaust plumes, flares, and reflections were identical second by second during the ascent. Like one camera was split to make both feeds.

Then on Thursday in the SpaceX launch video, it had changed and the exhaust plumes were obviously different. I can think up several possible explanations, but there was no notice attached regarding it having been edited.

I'm not really worried about it. I have no doubts, especially as so many people were there to see it launch and land, but I'd rather not have started watching the haters' videos flooding the place.
Rusty - Space Junky from way back.

It makes me laugh, You can see launches from the space center as far away as West Palm beach. Just go to the shore and look north any launches are readily visible. I was at the space center the Saturday before the launch ad saw the vehicle sitting out at the pad. Then went to the beach and saw the launch. Did not see the landing but I believe it happened. I can watch the reentry landings over and over. If anyting I thought it couldn't be that perfect, was almost convinced it was CGI.
Words Spoken by the first human to set foot on Mars... "Now What?"

Offline Jim Carter

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 550
Re: Space man in a Tesla -is the AC on?
« Reply #18 on: February 16, 2018, 09:22:07 AM »
.... I thought it couldn't be that perfect, was almost convinced it was CGI.
Don't worry!  The wife and I live in Titusville and were standing on the shoreline with one heck of a lot of people who witnessed the launch and the twin sonic booms, return and landing of the two boosters!  It was so totally kool. 

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #19 on: February 16, 2018, 03:19:08 PM »
    That was probably a copy-paste error. When they went to build the display, they wrote the HMTL for putting (say) the "right-hand" window on the display, then to put up the "left-hand" display, they copied the first one, pasted it in for the second, changed the position attribute to move it to the other side of the window, but failed to select which camera feed to use, so it was the same one. Later, they fixed it and remade the movie.
Brilliantly simple. Thanks, Brett.
Hopefully Youtube overlooked their normal policy and let them edit it in situ, so the url and comments remained in tact. If I was in charge of the 'Tube, I would have.
Rusty
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Fred Cronenwett

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1579
    • Lafayette Esquadrille
Re: Space man in a Tesla -is the AC on?
« Reply #20 on: February 16, 2018, 05:36:01 PM »
Hope they got Permanent registration tags and that the Airbag is still in working condition just in case it hits some space rocks

Fred
Fred Cronenwett
AMA 3879 - CL Scale
Model Aviation CL Scale columnist

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #21 on: February 16, 2018, 08:17:26 PM »
Brilliantly simple. Thanks, Brett.
Hopefully Youtube overlooked their normal policy and let them edit it in situ, so the url and comments remained in tact. If I was in charge of the 'Tube, I would have.
Rusty

  If you think it was brilliant, perhaps I should not mention how I managed to have such a deep insight into the issue. I certainly never spent hours chasing down a problem only to find that I had made a copy/paste error, so put that right out of your mind.

    Brett

Offline wwwarbird

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6611
  • Welcome to the Stunt Hanger.
Re: Space man in a Tesla -is the AC on?
« Reply #22 on: February 16, 2018, 09:17:37 PM »

 I've searched around a bit and haven't found any, are there any pics of the Telsa-naut space dude sitting in the car?


Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A.
IC C/L Aircraft Modeler, Ex AMA member

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #23 on: February 16, 2018, 09:28:35 PM »
I've searched around a bit and haven't found any, are there any pics of the Telsa-naut space dude sitting in the car?

Offline wwwarbird

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6611
  • Welcome to the Stunt Hanger.
Re: Space man in a Tesla -is the AC on?
« Reply #24 on: February 16, 2018, 10:14:19 PM »

 Thanks Brett. I haven't had much time to keep track of this whole event, is that supposedly an actual shot of the car out in space or just a photoshopped PR deal?

Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A.
IC C/L Aircraft Modeler, Ex AMA member

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #25 on: February 16, 2018, 10:38:05 PM »
Thanks Brett. I haven't had much time to keep track of this whole event, is that supposedly an actual shot of the car out in space or just a photoshopped PR deal?

  Real.

    Brett

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #26 on: February 17, 2018, 01:36:35 AM »
Quote
Brilliantly simple. Thanks, Brett.
  If you think it was brilliant, perhaps I should not mention how I managed to have such a deep insight into the issue. I certainly never spent hours chasing down a problem only to find that I had made a copy/paste error, so put that right out of your mind.

    Brett

Ah well, I didn't say "simply brilliant," I'm familiar with that copy/paste/oops drill too.

My thinking was more along the lines of a couple of techs saying,
"Hey Bert camera 1 is out!"
"No prob Bernie, just patch the #2 feed into it, nobody'll notice."
"Yeah, great idea, Bert. You're a genius."

HTML or some such code never occurred to me. In any case, I suppose we'll never know for sure.
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline RC Storick

  • From concept to reality
  • Administrator
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 11495
  • The finish starts with the first piece of wood cut
    • Stunt Hangar
Re: Space man in a Tesla -is the AC on?
« Reply #27 on: February 17, 2018, 06:53:14 AM »
It doesn't matter the dummy won't survive the Van Allen belt  LL ~. But here is a serious question. If the Van Allen belt has such high radiation how did the Apollo astronauts survive it in 1969 flying in a beer can?
AMA 12366

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #28 on: February 17, 2018, 10:33:31 AM »
They didn't pass through the widest part of it, they didn't stay in it long, and it's not the type of radiation that penetrates metal well. I'll let someone more qualified expand on that last part. They punched through and went to the moon. Six times. I'd hoped the LRO pictures would have settled it once and for all, but... silly me.

It won't be long before it's undeniable because there are a lot of plans in action by different parties who want to be there. It has resources, and at 1/6g you can really scram-ass outta there with a rocket on your ass, aimed at the asteroids or Jupiter, Saturn, and their moons. Boy I wish I had another 60 years to see it.
Rusty
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #29 on: February 17, 2018, 12:50:30 PM »
Ah well, I didn't say "simply brilliant," I'm familiar with that copy/paste/oops drill too.

My thinking was more along the lines of a couple of techs saying,
"Hey Bert camera 1 is out!"
"No prob Bernie, just patch the #2 feed into it, nobody'll notice."
"Yeah, great idea, Bert. You're a genius."

HTML or some such code never occurred to me. In any case, I suppose we'll never know for sure.

   If someone had done "view source" and saved it from the original page, you probably could have found the errant line!

    Brett

Offline FLOYD CARTER

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3208
    • owner
Re: Space man in a Tesla -is the AC on?
« Reply #30 on: February 17, 2018, 01:28:34 PM »
I have read reports that "space" is getting cluttered with old satellites and pieces of Space Junk which is not going to come down.

Putting more "junk" into space seems to be a reckless exercise in self-worship on the part of people with too much money and with no government restrictions.
"Growing old is easy.
 Staying old is hard"
AMA #796  SAM #188  LSF #020

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #31 on: February 17, 2018, 01:30:17 PM »
It doesn't matter the dummy won't survive the Van Allen belt  LL ~. But here is a serious question. If the Van Allen belt has such high radiation how did the Apollo astronauts survive it in 1969 flying in a beer can?

   Multiple reasons - they blew through it in a few minutes, and the "tin can" easily blocks most ionizing radiation. It does less well against gamma radiation but it may have cut the gamma flux by a factor of two or more. I saw the analysis somewhere, but it has been a while, so don't place any wagers on my recollection.

      The total dose for each astronaut was read out at least twice a day throughout the missions, and more for Apollo 8 (the first time through) and the total dose for the entire mission was negligible to very low and not medically relevant. As I recall, the dose from just the Van Allen belts was below one count on the dosimeters, again, you can read the entire air/ground transcript and onboard voice recorder transcript and get the relative doses at various points, or dig around and find the flight surgeons report where they have a plot of total dose over the missions.

     The "fake moon landing" nuts use the radiation as "proof" that it couldn't have been done. The reason that anyone pays any attention even a little bit is that the general public has an *insanely overblown and histrionic" idea of the actual danger of radiation exposure. One click of the Gieger counter and "we are all going to DIE!!!"

      Marie Curie spent most of her professional life discovering and then working with (and carrying around in her pockets) one of the most powerful radioactive elements, Radium. Yes, she died of radiation exposure and they buried her in a lead coffin. But, as it turns out, the radiation she died from was not ionizng radiation from Radium or other radioactive elements - it was X-Rays from the unshielded X-ray machine she used as a volunteer in World War I. There have been accidents that resulted in people getting acute radiation sickness at very high doses, getting over it, and living with it until they died of a heart attack at 80. The very small doses we are talking about here have never been proven to be detrimental in any way.   

     Of all the places in the world you might be worried about, you would think it would be Hiroshima and Nagasaki, Hiroshima in particular being caked with unreacted enriched uranium, since only about 2% of the nuclear materials in the bomb were actually consumed in the reaction before it disassembled itself. So, nuclear wasteland?  No, my minivan was made there, that's where the Mazda factory is. Chernobyl was even dirtier, and everyone has been evacuated for decades. It has turned into a nature preserve, despite the fact that you catch, say, a rabbit, and it's clearly full of radioactive plant leaves.

    The Apollo astronauts generally lived to ripe old ages, dying from the usual old man causes from the era of smoking and steak for breakfast. The few exceptions, particularly Jim Irwin, were almost certainly caused by something else, in the case of Irwin, severe potassium deficiency that built up due to dehydration during his Apollo 15 spacewalks. They were concerned by he and Scott (to a much lesser degree) developed abnormal heart rhythms, as they had an extended and very strenuous EVAs, particularly, trying to extract the core sample that got stuck. The flight surgeon said that he was on the ground, they would have had Irwin in the ICU after the first EVA. Of course, the capsule was pure oxygen and they made him wear the heart monitor leads for the rest of the mission, so it wasn't too far off from an ICU anyway. This led to an ridiculous overreaction by adding potassium to everything they took on 16, particularly the orange juice, which resulted in extreme flatulence and diarrhea  - which is not something you want to spend 10 days in a closed capsule with. On 16, when the frogmen opened the door, they slammed it back shut again, because the smell was so bad.  This, too was captured in the on-board voice, you can read the transcript if you want...

    The most serious radiation problem facing astronauts is X-rays from a solar flare. That really will go through conventional spacecraft materials like aluminum like sh*t through a goose, and the doses can be critical. Had there been a Class M or X solar flare during an Apollo mission, it could easily have been fatal. They paid a little bit of attention to sunspots at the time, and had there been an obvious threat they might have postponed the mission. It was a near miss on (again) 15, I think there was a flare right after they got back. Otherwise, statistics will tell you the threat, it's the likelihood of a sufficiently large flare during any particular 10 day period, aimed your way, you take your chances. For a year-and-a-half Mars mission, you absolutely have to deal with this somehow because it's likely to happen. It's a soluble problem, build a tantalum or lead shield, or use the water you are taking as a shield (A LOT of thickness of water is required, like a giant tank the long way through), aim it in the right direction, and shelter under it for a few minutes/hours.

     Most of what the public knows, or thinks it knows, about radiation is complete nonsense, and its by hyped to the stars by people wanting to cause people to be unreasonably frightened of it for reasons of politics/manipulation.

    Brett
   
p.s. Apollo 15 radiation exposure was 360 millirads for Scott and 510 millirads for Irwn (.36 and .51 rads). That's about a year's worth of exposure on the ground from natural sources. Scott's personal dosimeter failed and he took Worden's since he was going outside, so no personal reading for Al. The passive dosimeters (I think it was a film badge) were about 300 millirads. Here is a table from a source that I consider somewhat alarmist, but:

25   rad:   lowest dose that causes observable blood changes
200   rad:   local dose for onset of skin redness  in humans
400   rad:   predicted 50% chance of acute radiation sickness
1000 rad: predicted 100% chance of acute radiation sickness

   So, the exposure was around 1/50th of what it takes to cause detectable effects

p. p. s. Average Radiation Doses of the Flight Crews for the Apollo Missions
Apollo Mission
Skin Dose, rads
7    0.16    < low earth orbit below belts
8    0.16   < lunar orbit and through the belts
9    0.20  < low earth orbit below belts
10  0.48  < lunar orbit and through the belts
11  0.18  < lunar orbit, landing and through the belts
12  0.58  < lunar orbit, landing and through the belts
13  0.24  < lunar free-return loop and through the belts
14  1.14  < lunar orbit, landing and through the belts
15  0.30  < lunar orbit, landing and through the belts
16  0.51  < lunar orbit, landing and through the belts
17  0.55  < lunar orbit, landing and through the belts

     So it seems the exposure through the belts was much lower than the flight-to-flight variation - 7 and 8 were the same
« Last Edit: February 17, 2018, 08:40:51 PM by Brett Buck »

Offline RC Storick

  • From concept to reality
  • Administrator
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 11495
  • The finish starts with the first piece of wood cut
    • Stunt Hangar
Re: Space man in a Tesla -is the AC on?
« Reply #32 on: February 17, 2018, 02:42:59 PM »
I know nothing or try to think I know anything about space. But we can watch him live here.


Might be boring for a while.  LL~
AMA 12366

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #33 on: February 17, 2018, 02:50:42 PM »
I know nothing or try to think I know anything about space. But we can watch him live here.



Might be boring for a while.  LL~

   Not live any more, of course, by now, the Earth would be a tiny blue dot. And the batteries ran down a few hours after the third engine burn.

    It is definitely boring after a few minutes.

      Brett

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #34 on: February 17, 2018, 02:55:31 PM »
Thanks for the thorough radiation explanation, I'm glad I left it alone.

Brett, this is something I've wondered about for a long time now, but never had anyone to ask; If a booster with the power of a Saturn V(or now a BFR) was launched from the moon with a cargo of probes and satellites, how long could we estimate it would take to get to the outer planets? I'm guessing it would just go straight away from the moon. If not, then my question may be rubbish. But it seems like launching from the moon opens up the possibility of such ambitious missions.

At its extreme speed, could it then use gravity assists on the way, deploying its payloads and exiting on a heading to the next planetary system... forget Mars, drop off at Jupiter, then Uranus, Neptune, and off for a long ride to the Kuiper belt?

I hope this is even a reasonable question. One mission with a lot of return if it's even partially possible. Maybe the thing would need engine burns to hit multiple destinations, and that might be a big complication.
Rusty

DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #35 on: February 17, 2018, 03:01:52 PM »
I have read reports that "space" is getting cluttered with old satellites and pieces of Space Junk which is not going to come down.

Putting more "junk" into space seems to be a reckless exercise in self-worship on the part of people with too much money and with no government restrictions.

   Space junk is definitely a real problem, particularly in low Earth orbit. But in this case, they put it on an escape trajectory, so you have one 20x100 foot bit of debris that is easy to track, moving around in a huge volume of space enclosed by the orbits of Mars (aposelene) and the Earth (periselene).

      Brett
« Last Edit: February 17, 2018, 08:41:43 PM by Brett Buck »

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #36 on: February 17, 2018, 03:14:24 PM »
Thanks for the thorough radiation explanation, I'm glad I left it alone.

Brett, this is something I've wondered about for a long time now, but never had anyone to ask; If a booster with the power of a Saturn V(or now a BFR) was launched from the moon with a cargo of probes and satellites, how long could we estimate it would take to get to the outer planets? I'm guessing it would just go straight away from the moon. If not, then my question may be rubbish.

   The Saturn launch system, as used on Apollo, was pretty impressive in terms of capability, and could have launched deep space missions to some degree. Depending on the payload required (like a relatively small planetary probe like New Horizons), you would want an additional velocity stage, but it could be HUGE compared to most other comparable items, and get a probe to Pluto in very short order (a few years) compared to any of the alternatives. The Saturn V Mars missions used NERVA upper stages, which were nuclear-thermal engines, with extremely high performance  - roughly twice the specific impulse of the best chemical rockets (800 seconds VS 450).

   Now, you would be inclined to use a Hall Current Thruster, XIPS thruster, or some other ion thruster for such a mission, trading off acceleration for performance (1800 seconds VS 450). It woudn't work for a manned mars mission due to low acceleration.

    To get some idea of what was reasonably possible in terms of a manned mission, note:

https://en.wikipedia.org/wiki/Manned_Venus_flyby

     This looks at least plausible, and there were a lot of similar studies for other Saturn V missions that were generally possible from a technical standpoint. A manned flyby mission past Venus would have virtually *no* scientific value, but they probably didn't have enough information about Venus at the time to know about that. And they didn't care too much, they were trying to come up with reasons to keep building Saturn Vs. This mission has the same solar flare issue mentioned above, of course.

     Brett
p.s. I got curious about what a Saturn V interplanetary (interstellar as it turns out) mission using a 1800 sec Hall current thruster. I figure the giant boost capability would let me get a mass ratio of around 10 with a useful payload and a small reactor to power it, so I get 345,000 nautical miles/hour at burnout. That gets you to Pluto in around 15 months, (instead of 9 and a half years) when you figure a reasonable acceleration time and gravity. Unfortunately, it doesn't work well for a Pluto probe because you whip past in minutes because you are still going like a bat out of hades. But it catches Voyagers pretty quickly and keeps going. Also interesting is that you have to start considering *relativistic effects* like time/space dilation.
« Last Edit: February 17, 2018, 08:59:54 PM by Brett Buck »

Offline Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2718
Re: Space man in a Tesla -is the AC on?
« Reply #37 on: February 17, 2018, 04:27:37 PM »
  At first I was doubtful of the possibility of a booster being able to land without the aid of some sort of recovery system, from the stand point of how would you guide it? A spent booster??? A rocket is usually designed to go in one direction, and I didn't think the transmissions in them had a reverse!! LL~ On a typical launch, how far down range does a Falcon fly? I know that the rocket just doesn't go straight up. And at what point in the trajectory does it jettison the boosters>  How does it reverse course so it ends back more or less on the pad it took off from? The spent booster looks like anything BUT aerodynamic and any kind of ballistic shape. It definitely ain't pretty!! How far from the launch pad is the landing pad? It was definitely cool, and mind blowing that the two landed at almost t he same instant!
   Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #38 on: February 17, 2018, 08:01:08 PM »
  At first I was doubtful of the possibility of a booster being able to land without the aid of some sort of recovery system, from the stand point of how would you guide it? A spent booster??? A rocket is usually designed to go in one direction, and I didn't think the transmissions in them had a reverse!!

    The same way it goes up?  I have no direct knowledge for SpaceX, but based on what I have seen, nothing seems too complicated once you have a closed-loop guidance system and autopilot. I think in this case, the boosters separate, it shuts down 6 of the 9 engines, pitches up and brakes while climbing. It knows where it is, how fast it is going and what angle it is pointing from the inertial guidance system (gyros and accelerometers, probably with GPS for external "truth" when available). With that information and some math, it probably predicts the impact point on the earth, driving it to intersect the landing site. When it reaches a predicted impact near the landing site, it shuts down, and lets gravity to the job, and flipping around to align the engines with the velocity vector using "grid fins" near the nose.

   It keeps predicting the remaining altitude and delta-V, and calculating the required throttle setting to remove the remaining velocity. When the throttle setting gets to maybe 75%, you start the engines at 75% throttle, then start using radar or inertial nav/GPS or some sort of terminal radio guidance to adjust the throttle and attitude to get to impact point and get the velocity to be ~10 feet/second at about 50 feet altitude, then hold a constant velocity until touchdown. Limit switches on the legs indicate landing and shuts everything off.

    I am not sure how the autopilot itself works, I would guess that it uses gimballed engines, with an attitude control system that accepts guidance commands (commanded body rates) from the guidance system, integrating those to get an attitude, then controlling the error in the attitude to zero by angling the engines to get the desired angular acceleration generated by the attitude control law. The way the engines are arranged, that's why you need 3 of them.

    You have to keep thrusting through the separation, to keep positive acceleration on the propellant so they are near the pickups. And sometimes, it certainly does flip around and fly "backwards" as it is accelerating back towards the landing pad. There's not much air at those altitudes.

       It's all pretty straightforward. Importantly, most of the same things have to happen on all boosters on the way up! This is just more of the same. Usually when a rocket takes off, it goes "open loop" for a while to make sure that small errors don't cause large steering commands to tilt it over and hit the pad. After that, they are driven along a "gravity turn" where the body of the rocket is maintained in alignment with the velocity vector, so it doesn't come apart due to aerodynamic forces. It's keeping track of its position and velocity all the way up. At some point, at a high enough altitude that you can steer it,  the guidance law becomes active, and steers the rocket back to the planned trajectory by aiming it in the direction it needs to go by issuing commands to the autopilot. Once that converges, it flies along the desired trajectory until the required velocity is reached, then cuts off.

   In this case, instead of cutting off, the system continues to operate with a new target trajectory and impact point, until the impact point is the landing pad.

The only reason that others haven't done something similar is that it's too costly in terms of payload/throw weight, because you have to reserve a fair bit of fuel to fly it back and land. The boosters can fly back because its' pretty close and they save a lot of fuel. The core continues on forward and lands on a ship in the ocean near where it would have hit anyway, saving fuel. 

    The autopilot part of it is absolutely nothing new, nearly every space booster and every three-axis stabilized spacecraft has something similar, and they aren't far from and/or adapted from aircraft autopilots dating back much furthers. Early boosters like the Atlas used radio guidance, tracking the missile on the ground with radar, seeing where it is going, then radioing the rate commands to the autopilot.

    Very quickly, it became possible to put an inertial guidance sensors in the rocket itself, so it was independent of the ground, with variants of increasing performance over the years. Even the V-2 hd a crude version (which didn't work too well and isn't so accurate, good enough for a 200-ish mile IRBM but not nearly good enough for a 10,000 mile ICBM) of inertial guidance.


Quote
LL~ On a typical launch, how far down range does a Falcon fly? I know that the rocket just doesn't go straight up. And at what point in the trajectory does it jettison the boosters>  How does it reverse course so it ends back more or less on the pad it took off from? The spent booster looks like anything BUT aerodynamic and any kind of ballistic shape. It definitely ain't pretty!! How far from the launch pad is the landing pad? It was definitely cool, and mind blowing that the two landed at almost t he same instant!

   I honestly don't know, but I expect it would just take a bit of googling to find out, it's not classified. As far as aerodynamics go, it's probably pretty draggy but it uses fins near the nose to stabilize it in the "tail first" direction when the engines quit. The are "grid fins", not fins like an arrow, which are very draggy but easy to build and light. The Soviets use them to stabilize the Soyuz during aborts, too, and it works fine as long as you don't care about drag (since that is primarily how they work, vice arrow-style fins that work primarily by lift).

     Google is your friend.

    Brett

p.s.   None of this is new, in fact, if you want a moderately extensive discussion of it, try:

https://www.hq.nasa.gov/alsj/a15/A15Delco.pdf  LARGE PDF!

    Which is how it worked on the Apollo 15 Lunar Module, to the point of providing wall-to-wall schematics for the do-it-yourselfer. Useful information in case you should be suddenly called upon to take over a mission to Hadley Rille.  Look at the "Science" section located at about 75% towards the end, the pages are labelled "SC-xx", SC-18 is how the CSM takeover of the booster works and is typical. I routinely use SC-28 to SC-31 for a reference for new hires as to the basics of mass-expulsion (thrusters) attitude control, SC-36 starts a discussion of EXACTLY what you need to know to guide a rocket-propelled item to a specific point on a celestial body, and I spent some time evaluating the very interesting "time division multiplexing" system for using thrusters and a slow thruster gimbal simultaneously.
« Last Edit: February 18, 2018, 12:16:38 PM by Brett Buck »

Online George Albo

  • 2018 Supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 325
Re: Space man in a Tesla -is the AC on?
« Reply #39 on: February 17, 2018, 09:09:24 PM »
It makes me laugh, You can see launches from the space center as far away as West Palm beach. Just go to the shore and look north any launches are readily visible. I was at the space center the Saturday before the launch ad saw the vehicle sitting out at the pad. Then went to the beach and saw the launch. Did not see the landing but I believe it happened. I can watch the reentry landings over and over. If anyting I thought it couldn't be that perfect, was almost convinced it was CGI.
Can see launches further south: Broward County- at night - spectacular
All things come to those that wait. If you want it any faster, you'd better move!:)

Offline Gary Dowler

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 269
Re: Space man in a Tesla -is the AC on?
« Reply #40 on: February 17, 2018, 09:51:00 PM »
Brett, thank you for taking the time to type that out. Some of it is a little over my pay grade, nonetheless I find such posts extremely interesting and informative.

Gary
Profanity is the crutch of the illiterate mind

Offline Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2718
Re: Space man in a Tesla -is the AC on?
« Reply #41 on: February 17, 2018, 09:58:45 PM »
    Yes, thanks for the in depth explanation. Went back and watched the launch and recovery video again and I can see the what's going on now. The video is a little hard to make out in spots. It's just so different from what one gets ingrained in his mind after watching lift offs since 1960! I just could not imagine "flying" the boosters back to the pad, but that is what is happening.
   Type at you later,
    Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #42 on: February 18, 2018, 02:21:41 AM »
I was searching for amateur movies of the launch and booster landings, and found one that is by far the clearest and best video I have seen. It's really worth watching, especially the separation and decent of the side boosters.
This one is worthy of adding to your favorites.
Rusty

Watch in full screen if you can.

DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Bill Adair

  • 2018 Supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 783
  • AMA 182626
Re: Space man in a Tesla -is the AC on?
« Reply #43 on: February 18, 2018, 03:05:09 AM »
Rusty,

Thanks for adding yet another fine video of the launch.  H^^

Bill
Flying control line again, after a forty-nine year break!

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #44 on: February 18, 2018, 12:15:39 PM »
I was searching for amateur movies of the launch and booster landings, and found one that is by far the clearest and best video I have seen. It's really worth watching, especially the separation and decent of the side boosters.

   Several things that deviate from my explanation - looks like they have reaction controls to maintain the attitude in addition to grid fins, and on this return at least, they had to do a trim maneuver on the way down. The attitude control on the way down is clearly thrust vectoring with gimballed engines.

    Brettt

Offline Phil Krankowski

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 995
Re: Space man in a Tesla -is the AC on?
« Reply #45 on: February 18, 2018, 01:39:52 PM »
Here is Spacex's explination.
http://www.spacex.com/news/2015/06/24/why-and-how-landing-rockets
Cold gas thrusters, grid fins, and more.
Yes, there is some vector control in the engines in addition to creating some torque by choosing which engine is lit.  The latest generation of Merlin engine has some throttle control.
https://en.m.wikipedia.org/wiki/Merlin_(rocket_engine_family)

Pretty cool stuff
Phil

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #46 on: February 18, 2018, 02:29:43 PM »
Yes, there is some vector control in the engines in addition to creating some torque by choosing which engine is lit.  The latest generation of Merlin engine has some throttle control.

      As an aside, the Soviet N1 used 30 engines, 26 of which where throttled, and differential throttling as the sole attitude control method. That's also why it failed repeatedly, because it was/is very difficult to make it work reliably, particularly with mid-late 60's era Soviet electronics. All 4 flights failed, all due to engine problems related to KORD (the throttle/attitude control method).

   One of my favorite achievements is designing a similar system using 8 engines and PWM "throttles" (vice steady-state firing with variable thrust). I also consulted with the guys on the ill-fated Mars Polar Lander on a similar system using 12 engines. Unfortunately it was AFTER IT HAD BEEN LAUNCHED, which limited the possibilities for improvements (which they definitely needed), but ultimately the failure was likely unrelated to this system, it probably would have worked *if it hadn't been turned off at 10,000 feet* causing a likely death plummet.

    Brett

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #47 on: February 18, 2018, 04:23:44 PM »
Yeah, that Polar Lander was a huge disappointment. Not to mention, an embarrassment.

I remember watching the early Falcon barge landing attempts. That vectored exhaust really had it dancing around as it approached the deck. I think they have lock-down clamps now, but I've seen one successfully land standing up a couple of meters away from the center of the target
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 8468
Re: Space man in a Tesla -is the AC on?
« Reply #48 on: February 18, 2018, 06:55:37 PM »
Yeah, that Polar Lander was a huge disappointment. Not to mention, an embarrassment.

  It's always a bad sign when the failure report both fails to narrow it down to a root cause, but comes up with 4-5 different possible fatal conditions, any one of which could have been fatal.

   The part of the system that I was (very peripherally) involved with was analysis of the propulsion system for the landing, and even more remotely, the control system design (PWM "throttling" and associated factors). One of the issues was "water hammer", where you get waves oscillating around in the propellant from opening and closing the thruster valves, which in this case, happened 10x a second. They were trying to model it, and as luck would have it, we needed someone to model our system, too, and had also acquired extensive in-flight data on the topic. They used our data and a model of our system to validate their modeling technique - they built our system, and predicted the response, and then compared it to the actual data from flight. Then they used the same principles to model their own system, and predict theirs (which couldn't be test-fired since again, *they had already launched it*). The results are mentioned in the failure report, at some places in the system with a static pressure of 400 psi or something like that, the peak pressure spike was something like 2200 psi, far above the proof pressure.

   This very difficult and costly to test on the ground, of course. Eventually, they restarted the sister program, added a bunch of additional testing that they wanted to do, but cost too much first time. Among the testing and analysis they did was to actually do a water-hammer test (using water instead of fuel) with the full-up system as built. The movie of it is here:

https://www.nasa.gov/mission_pages/phoenix/images/press/hammer-test.html

    Note that it changes the firing pattern as it goes on, and the final bit of it is what we thought was the worst case for MPL, 50% duty cycle (on for 50 milliseconds, off for 50 milliseconds, repeating every 100 milliseconds).

    I might add that we never actually did a ground test nor a very good analysis either, and ALSO had some problems, although not fatal, in fact it worked more-or-less OK for several years. That's why we wanted them to analyze it in the first place.

   Of course, Mars Phoenix was highly successful, even though it was nearly identical to Mars Polar lander.

    Note that the general topic of waves rattling around in tubes is *highly relevant* to model airplanes, since the basic issues with water hammer (particularly resonant water-hammer) are mathematically identical to tuned exhausts on stunt planes.

      Brett


p.s. I might add, these problems were blamed on the "faster-better-cheaper" plan that NASA adopted. But they knew that they were adding risk by cutting costs - so that they could get more missions for a given budget. Cut the mission cost to 1/3 of what it would have and you can have 3x as many of them - meaning they could tolerate more failures and still have a given number of successful missions. Get lucky, and you have more successful missions than if you spent more money to increase the chance of success. And bear in mind, even massive analysis/review/testing costing an astronomical amount of money doesn't guarantee success. So there is *always* a trade-off to be made between some aspect of cost, schedule, and risk, depending on the external drivers. Almost everyone involved understands this pretty well, and all the argument we have over the topic is over putting our efforts in the areas that will make a difference without incurring unreasonable impacts.

   NASA in particular has a real dilemma - they built up an amazing amount of knowledge about project management that they incorporated into their culture and requirements. But most of it came during the manned spaceflight era, where schedule and risk were the key drivers, and cost was incidental. When you have cost constraints, you want to change the equation a bit, but you have all these rules about what you are required to do.

     Faster-better-cheaper was an attempt to skip some of the "required" items that were believed to be disproportionately costly for their value in reducing risk, particularly multiple layers of review. They did OK on that, they tried maybe 10 missions this way, had 5-6 excellent successes. If they had done it the old way, they may have only tried 3 missions, maybe all successful, but 3 is less than 6. What was not figured in was that their own past success set them up for a lot of criticism when they did have a failure, and the general public wasn't really tolerant of it.
     
« Last Edit: February 19, 2018, 10:42:57 AM by Brett Buck »

Offline RknRusty

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2425
    • My Tube channel
Re: Space man in a Tesla -is the AC on?
« Reply #49 on: February 18, 2018, 10:13:48 PM »
Yeah, that Polar Lander was a huge disappointment. Not to mention, an embarrassment.
Now I realize when I wrote that comment, I had Polar lander and Climate Orbiter confused with each other. I was thinking of the English/metric mixup that tore up the Orbiter as being the embarrassment.
My mistake, sorry about that.

Not too long after that, if I recall correctly  ::), another craft had to do some extensive and unnerving aerobreaking, but finally succeeded in making a soft landing. That was an impressive save.
Rusty
DON'T PANIC!
Rusty Knowlton
... and never Ever think about how good you are at something...
while you're doing it!

Jackson Flyers Association (a.k.a. The Wildcat Rangers(C/L))- Fort Jackson, SC
Metrolina Control Line Society (MCLS) - Huntersville, NC - The Carolina Gang
Congaree Flyers - Gaston, SC -  http://www.congareeflyer.com
www.coxengineforum.com


Tags: