News:



  • July 05, 2025, 03:32:38 PM

Login with username, password and session length

Author Topic: A question for Brett  (Read 6346 times)

Offline Warren Walker

  • 25 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 309
A question for Brett
« on: September 01, 2016, 06:10:39 PM »
In the story I read about the Space x rocket explosion, it said the satellite cost 150M.
How much was the rest of it worth? Rocket, fuel, launch pad, man hours, just wondering.

W.W.
 

Offline Dennis Moritz

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2485
Re: A question for Brett
« Reply #1 on: September 01, 2016, 06:43:23 PM »
Not much now


Sent from my iPhone using Tapatalk

Offline RknRusty

  • 2019 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2687
    • My Tube channel
Re: A question for Brett
« Reply #2 on: September 01, 2016, 10:31:57 PM »
Apparently the fueling system caught fire while filling the Falcon's tank prior to the test run. The sattelite, to be used for broadband Internet access to poorly connected areas in the region, was also destroyed, but insured for its full value of $286 million. Sucks for facebook users in remote areas. I linked to that LA Times story from SpaceX.com.
http://www.latimes.com/business/la-fi-space-x-explosion-20160901-snap-story.html.
I don't know the rest of the cost.
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: 14501
Re: A question for Brett
« Reply #3 on: September 02, 2016, 12:50:52 AM »
In the story I read about the Space x rocket explosion, it said the satellite cost 150M.
How much was the rest of it worth? Rocket, fuel, launch pad, man hours, just wondering.

   I am far from an expert on the SpaceX costs, but I think they are charging about $60-70 million per launch, which may be operating at a loss. That's much less than an Atlas launch which I could price out, but might be something like $200 million. Today, clearly, they had substantial damage to the pad and support equipment, so figure maybe $20 million for that. Those are all slightly better than guesses, but it's within an order of magnitude. What it will cost them in the long run is TBD, but it wouldn't surprise me if Musk had to insure the next few on his own dime.

     I would have to dispute the description of the failure. It seemed pretty clear that the second stage exploded, not just catch fire. That's quite puzzling. I think we all expected that there was some sort of a  tank vent valve issue that caused the tank to burst (as the LOX boiled off), then caught fire. But it was far too sharp an explosion for a mere leak, even a severe leak. I don't know how their tanks work, but if it had a common bulkhead, that could have leaked LOX into the fuel tank, and then it's just a matter of a sharp impact or tiny initiating event followed by a very bright and fast disassembly. Essentially, this kind of tank is a single more-or-less cylindrical tank, with a single bulkhead across the middle to separate the fuel and oxidizer. This still follows the LOX vent valve icing or failure theory, except that instead of bursting the side of the tank, it burst or separated the common bulkhead and leaked internally.

   Once the second stage blew, it collapsed on the first stage, causing a bigger but much less sharp explosion and fire at the base of the pad. Then, the injection/upper stage, payload, and payload fairing, still held by the gantry, pulled the top of the gantry to the side, then tipped over and fell to the ground. At that point, it clearly burst the tanks and exploded the upper stage, so that's a third big blow up and fire. The service tanks blew in the fire, and then towards the end, the spacecraft propulsion also blew with a relatively small pop.

   Several other interesting questions are raised. First and most obvious is why they want to do a static test in the first place. That was common early on, but later mostly abandoned as not particularly insightful. Any firing is a risk. If the static test is good, you learn nothing useful because it would have worked in a real flight anyway. If it doesn't work, aside from a few minor failure modes, it will blow and wreck the whole thing anyway, and at best you haven't damaged the payload. Which brings up the next obvious question, why do it with the payload stacked?  This eliminates almost any value to the test, because you are taking almost all the risk you would in a real launch. When they did it on the Atlas back in the 50's/60's, they didn't do it with a live H-bomb on top, and they didn't ask John Glenn to climb up there and ride it out, because if it does blow, you kill everybody so the only reason to static test is to test the relatively cheap rocket before you risk the payload. The way they did it, you gain almost nothing.   Third question is why, if you are doing a static test, do you also fuel the upper stage. You sure aren't going to static test that, it's sitting on the rest of the rocket, so why bother fueling it. Usually, fueling tests are done completely independent of a static test. or at most you do the lower stage fueling test and static test, and do the upper stage fueling tests later.

    I have to say, I don't have a lot of sympathy for Musk and company. They have spent the last 5+ years telling everyone how stupid and backwards everyone else is, particularly the experienced contractors like ULA. I have no great love for ULA, either, but having 50+ years of experience has at least taught them to be very careful. Musk, Rutan, et al seem to operate on hubris. Perhaps they are learning some hard lessons and humility, but no evidence of it so far.

   One thing I have learned over the years operating in the most stressing and difficult environments is that no one is smart enough to slap-dash it and beat the odds for long. You can never be *too* rigorous or careful. Knowing that is largely *why* ULA costs 5x as much. Even that doesn't guarantee success, but is sure raises the odds. It can be a very humbling business and one single mistake can destroy tens of millions, hundreds of millions, or billions of dollars and maybe kill a bunch of people.

     Brett

p.s . in case anyone hasn't seen it, heres the definitive video. Money shot at about 1:11 and definitely turn on the sound:

« Last Edit: September 02, 2016, 03:31:16 AM by Brett Buck »

Offline Chris McMillin

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1917
  • AMA 32529
Re: A question for Brett
« Reply #4 on: September 02, 2016, 09:20:34 AM »
Thanks for a frank report, man. I'd love to see that vid with the sound syncronized but the evidence as presented is very impressive. I simply cannot imagine a static test outside of a test environment/procedure either, ie payload on top is dumb. If I owned the payload I would've bitched big time knowing that plan! So dumb.
As dumb as the Rutan guy unlocking the wing in highspeed flight;
Or ground level pressurizing the Apollo 1 two additional pounds while pumped full of 100% O2.
Just very weird where people act as if they do not understand the basics while actually operating the real vehicles. I guess it happens more than we would like to think?
Chris...

Offline pat king

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1353
    • PDK LLC
Re: A question for Brett
« Reply #5 on: September 02, 2016, 12:40:21 PM »
I think the sound is off because of the distance of the camera from the vehicle. I would guess the long lens on the camera makes us think it is significantly closer to the bird than it is.
We all make mistakes, but even more so when the people are not qualified to be doing what they are.

Pat
Cryogenic Fluids Production Specialist
USAF 1965-1969
Pat King
Monee, IL

AMA 168941

Offline Fredvon4

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2101
  • Central Texas
Re: A question for Brett
« Reply #6 on: September 02, 2016, 01:05:14 PM »
Pat said..."We all make mistakes, but even more so when the people are not qualified to be doing what they are."

I say....Or deliberately willing to IGNORE 7+ decades of best practices in the testing community...all well and thoroughly documented

Perhaps Brett's opining about their egos (implied) hubris and apparent lack of humility is spot on...

Fred
US Army Test and Evaluation Officer 2001~2014

I wrote dozens of Event Design Plans for simple $20M projects up to a few $64B systems

I did not work the missile system tests at White sands or the (formerly Kwajalein Missile Range) Ronald Reagan Ballistic Missile Defense Test Site, commonly referred to as the Reagan Test Site. But I did work closely with, or went to school with ( Acquisition training) about 12 of those Test officers. From conversation I know we would have NEVER designed a test the way this one was done

I find Brett's observation in line with my own curiosity about the static test....
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #7 on: September 02, 2016, 02:00:29 PM »
Pat said..."We all make mistakes, but even more so when the people are not qualified to be doing what they are."

I say....Or deliberately willing to IGNORE 7+ decades of best practices in the testing community...all well and thoroughly documented

  That's what is so frustrating, and it happens over and over. The issue with the roll/yaw coupling on SS1, for example, is basic knowledge (that sweep has a dihedral effect and extreme sweep, or extreme effective sweep (like a lifting body or SS1) has extreme dihedral effects) and has been demonstrated in both technical literature in pop culture since the 60's. The opening sequence of "Six Million Dollar Man" showed it. You almost have to willfully ignore it to not know about it.

   Same with a lot of this stuff, the worst case of hubris probably being the second stage of Falcon 1 going unstable. It is definitely a hard problem to stabilize a gimbal-controlled rocket stage throughout an entire fuel burn, the inertia changes by a factor of 10, the mass/acceleration by a factor of 5 or so, and thus the slosh effects vary widely over the mission. But, one thing I do know, is that running 100,000 simulations, tweaking the gains by eye until it looks about right, is not a robust solution. That's why the "dinosaurs" cost a lot and take a long time, everbody did that already and found out the hard way.

  The worst from a cost standpoint is an rocket engine test at the Mojave airport parking lot with rubberneckers gathered around, and getting, as I recall, 3 people killed in an entirely avoidable explosion from a very well known phenomenon.

   The people pioneering everything learned a lot of hard lessons - because there was no other way - and they are very well documented. It's always going to be a risky venture and you can never analyze away every problem. But you darn well better be willing to take advantage of the hundreds of disasters and followups that people already know about. Or, let your own arrogance get in the way, and learn it all for yourself from scratch.

    Brett

Offline Tim Wescott

  • 25 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12904
Re: A question for Brett
« Reply #8 on: September 02, 2016, 02:34:43 PM »
   Same with a lot of this stuff, the worst case of hubris probably being the second stage of Falcon 1 going unstable. It is definitely a hard problem to stabilize a gimbal-controlled rocket stage throughout an entire fuel burn, the inertia changes by a factor of 10, the mass/acceleration by a factor of 5 or so, and thus the slosh effects vary widely over the mission. But, one thing I do know, is that running 100,000 simulations, tweaking the gains by eye until it looks about right, is not a robust solution. That's why the "dinosaurs" cost a lot and take a long time, everbody did that already and found out the hard way.

Do you know that they did that, or do you just surmise that from the thing's behavior?

'cause, I sometimes advocate seat-of-the-pants loop tuning, but only in cases where the problem is easy to solve and no one is going to get as much as a paper cut if things go haywire.  There's no excuse to not do it right (particularly since doing it right followed by 10,000 simulations to verify costs less than 100,000 iterations of doing it wrong).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Warren Walker

  • 25 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 309
Re: A question for Brett
« Reply #9 on: September 02, 2016, 09:16:45 PM »
Thanks for the info Brett, as always, you paint a great picture in the way you explain things.

W.W.

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #10 on: September 02, 2016, 09:38:23 PM »
Thanks for a frank report, man. I'd love to see that vid with the sound syncronized but the evidence as presented is very impressive.

The sound is unsynchronized only because the microphone is at the camera, and both are several miles/10 seconds away.

 
Quote
I simply cannot imagine a static test outside of a test environment/procedure either, ie payload on top is dumb. If I owned the payload I would've bitched big time knowing that plan! So dumb.
As dumb as the Rutan guy unlocking the wing in highspeed flight;
Or ground level pressurizing the Apollo 1 two additional pounds while pumped full of 100% O2.
Just very weird where people act as if they do not understand the basics while actually operating the real vehicles. I guess it happens more than we would like to think?

     Yes, and it would certainly be interesting to have an entirely independent objective investigation into the SS2 issue to see if that was really true. It certainly works out conveniently  for the company that there's nothing wrong with the design, just a random pilot error that can be solved by better, and very inexpensive, training.

For Apollo 1, they had to maintain positive pressure to do the test. It was not designed to take pressure from the outside. The two PSI was not, all by itself, outrageous. Apollo 1 was a different set of forcing functions/drivers and a different type of hubris. Any of the individual design decisions was more-or-less justifiable, but the execution was not up to par.

     For instance, a pure oxygen environment was absolutely necessary, and they we might still be trying to build a large enough rocket to do the mission otherwise. If you wanted to use a sea-level atmosphere, that probably triples the weight of the lunar module - you would have to build the ascent stage twice as heavy to take the pressure, meaning the descent stage might have to be twice or 3x as big to be able to land it.

      Even at 5 psi, the lunar module blew up like a metal balloon, with the door bulging out in the middle because it was so light. At 14.7 psi, you also have to have a pretty large airlock that operates at 3.5 or so psi pure oxygen anyway, because you sure can't run the spacesuits at 15 psi, and you have to pre-breath for hours, so the mission is greatly extended - meaning bigger batteries, change to fuel cells, or other immense complications. Or, run the CM at 14.7 and the LM at 4.5 pure oxygen, with an airlock  between. Then you have to wait for hours to transfer from one to another, lengthening the mission and adding immense risk.

    Any of that would mean something substantially larger than a Saturn V, once you add up all the extra weight.

    There were certainly other possible workarounds, like the one they ended up with (start with atmospheric pressure and nitrogen and let it leak down slowly to 5 psi before you get in the LM). What was more-or-less unconscionable was the workmanship of the CM, and the excessive flammable materials. It's not like they didn't know better, fire prevention was a known design issue.


    Brett

Offline RC Storick

  • Forum owner
  • Administrator
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12567
  • The finish starts with the first piece of wood cut
    • Stunt Hangar
Re: A question for Brett
« Reply #11 on: September 03, 2016, 08:09:43 AM »

p.s . in case anyone hasn't seen it, heres the definitive video. Money shot at about 1:11 and definitely turn on the sound:


NO SMOKING
[/b]
AMA 12366

Offline david beazley

  • 2017
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 442
Re: A question for Brett
« Reply #12 on: September 03, 2016, 12:49:15 PM »
Geez, now there are nome conspiracy theorists saying it was attacked by a drone.
http://www.dailystar.co.uk/news/latest-news/542878/spacex-rocket-explosion-elon-musk-falcon-9-attacked
I guess PT Barnum was right. 
It's only paranoia if they aren't really after you.
Analog man trapped in a digital world
AMA # 2817

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #13 on: September 03, 2016, 01:35:33 PM »
Geez, now there are nome conspiracy theorists saying it was attacked by a drone.
http://www.dailystar.co.uk/news/latest-news/542878/spacex-rocket-explosion-elon-musk-falcon-9-attacked
I guess PT Barnum was right. 

   The object they show could be very-fast-moving and close to the rocket, or slow-moving and close to the camera. Easy to misinterpret with the extreme foreshortening effect of very long lenses.

    Apparently they use TEB (triethyl borane) as part of the ignition system, which can be used safely but is definitely a problem if there are any leaks. I sure wouldn't fill the second stage TEB tank for a static test, but there's another possible ignition source.

   There are plenty of potential failure modes for any rocket, it will be interesting to see if they ever come up with one, and if the public statements are consistent with the evidence.

      Brett

Offline Douglas Ames

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1299
Re: A question for Brett
« Reply #14 on: September 03, 2016, 04:19:13 PM »
 Snip> I have to say, I don't have a lot of sympathy for Musk and company. They have spent the last 5+ years telling everyone how stupid and backwards everyone else is, particularly the experienced contractors like ULA. I have no great love for ULA, either, but having 50+ years of experience has at least taught them to be very careful. Musk, Rutan, et al seem to operate on hubris. Perhaps they are learning some hard lessons and humility, but no evidence of it so far. <

I've read this in other places also. They really need to suck it up and change their mindset.
NASA and the Aerospace Industry have decades of experience. Mostly success, but they learn from their failures.
AMA 656546

If you do a little bit every day it will get done, or you can do it tomorrow.

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #15 on: September 03, 2016, 05:14:07 PM »
Snip> I have to say, I don't have a lot of sympathy for Musk and company. They have spent the last 5+ years telling everyone how stupid and backwards everyone else is, particularly the experienced contractors like ULA. I have no great love for ULA, either, but having 50+ years of experience has at least taught them to be very careful. Musk, Rutan, et al seem to operate on hubris. Perhaps they are learning some hard lessons and humility, but no evidence of it so far. <

I've read this in other places also. They really need to suck it up and change their mindset.
NASA and the Aerospace Industry have decades of experience. Mostly success, but they learn from their failures.

   The fanbois are even worse. Like this:

http://thefreethoughtproject.com/watch-elon-musk-nasa-school-children-lands-rocket/

     NASA and Von Braun considered this during the initial Saturn C1-C5 designs in the late 50's.  But they rejected it because it *costs something like 30% of the throw weight* both from the fuel you have to reserve for the landing, and for the landing gear, heat shield, etc, for some hypothetical saving on recurring costs, and the additional risk of flying something  multiple times.

   Just to be clear, I don't fault them at all for having failures. Search for "early rocket failures" and see how many there were originally. Failures are a necessary element to develop something like this. I do fault them for either not being aware of the vast database of experience, or not knowing about it, all the while claiming to be geniuses for ignoring it.

    Brett
« Last Edit: September 03, 2016, 07:48:01 PM by Brett Buck »

Offline Tim Wescott

  • 25 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12904
Re: A question for Brett
« Reply #16 on: September 04, 2016, 11:56:37 AM »
  The fanbois are even worse. Like this:

http://thefreethoughtproject.com/watch-elon-musk-nasa-school-children-lands-rocket/

     NASA and Von Braun considered this during the initial Saturn C1-C5 designs in the late 50's.  But they rejected it because it *costs something like 30% of the throw weight* both from the fuel you have to reserve for the landing, and for the landing gear, heat shield, etc, for some hypothetical saving on recurring costs, and the additional risk of flying something  multiple times.

   Just to be clear, I don't fault them at all for having failures. Search for "early rocket failures" and see how many there were originally. Failures are a necessary element to develop something like this. I do fault them for either not being aware of the vast database of experience, or not knowing about it, all the while claiming to be geniuses for ignoring it.

    Brett

Yes, clearly we should use something sensible, like a Lofstrom loop.  It looks like it needs more power than is available from a small block Chevy engine -- maybe a 427 or two?
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #17 on: September 04, 2016, 12:31:57 PM »
Yes, clearly we should use something sensible, like a Lofstrom loop.  It looks like it needs more power than is available from a small block Chevy engine -- maybe a 427 or two?

   The obvious solution is to power the loop with unicorns on a treadmill.

     Brett

Offline Russ Popel

  • 21 supporter
  • Trade Count: (0)
  • New Pilot
  • *
  • Posts: 14
Re: A question for Brett
« Reply #18 on: September 04, 2016, 01:29:37 PM »
Just to expand this interesting topic a little,Brett what's your impression of the Russian program? I assembled and flew a Soviet trainer jet and was taken with how they did things different ,yet quite simple and ingenious .

Offline FLOYD CARTER

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4503
    • owner
Re: A question for Brett
« Reply #19 on: September 04, 2016, 02:09:13 PM »
The basic NASA problem is that they tended to be just too cautious, and they over-designed, and over-tested everything, until the costs got too much for even our "spend-happy" government to tolerate.  So, enter the private sector, saying they could to the same job at far less cost.

These figures of 200-300 million $ for one payload, or one launch vehicle, even for private industry, is a little frightening to me. 

I'm just thankful that this launch failure didn't cost the taxpayers (well, maybe some).

Floyd
91 years, but still going
AMA #796  SAM #188  LSF #020

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #20 on: September 04, 2016, 02:55:32 PM »
The basic NASA problem is that they tended to be just too cautious, and they over-designed, and over-tested everything, until the costs got too much for even our "spend-happy" government to tolerate.  So, enter the private sector, saying they could to the same job at far less cost.

  Particularly since it's very easy to say you can do things, and not so easy to actually do it.

      Brett

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 14501
Re: A question for Brett
« Reply #21 on: September 04, 2016, 03:09:17 PM »
Do you know that they did that, or do you just surmise that from the thing's behavior?

'cause, I sometimes advocate seat-of-the-pants loop tuning, but only in cases where the problem is easy to solve and no one is going to get as much as a paper cut if things go haywire.  There's no excuse to not do it right (particularly since doing it right followed by 10,000 simulations to verify costs less than 100,000 iterations of doing it wrong).

   That's what people very close to the process tell me they did. Hand-tuning the gains is one thing- to some extent, there is always some art to it. It's another to dispense with analytical work entirely and just run a bunch of simulations and hope you hit the right conditions somewhere in there at random.

   I know for direct fact that other of the new-space people don't know what they are doing. Carmack was on sci.space. <<something>> explaining why timing didn't matter and Windows RT was plenty good enough for the operating system - for his *gimbal loop* that probably needed to run at 120 hz+. He explained that they had done hundreds of simulations with random timing jitter and thus proved it. OY!  Even the Orion service module, which uses an old OMS pod engine and gimbal control, uses an analog system for the servo loop, partly because no one could build a discrete-sampled system fast enough. It's particularly bad when you take the gigantic OMS engine that used do push around the big old orbiter, and stick it to the back of the relatively tiny Orion CSM.

     Brett

Offline Dennis Moritz

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2485
Re: A question for Brett
« Reply #22 on: September 04, 2016, 04:24:25 PM »
The Space Shuttle is a reusable. I met a fellow at Brodak who worked on it. He said it would have been vastly more cost effective to continue missions using the shuttle. No doubt very different from using a reusable rocket stage. Why was the shuttle abandoned?


Sent from my iPhone using Tapatalk

Offline Tim Wescott

  • 25 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12904
Re: A question for Brett
« Reply #23 on: September 04, 2016, 05:07:29 PM »
   That's what people very close to the process tell me they did. Hand-tuning the gains is one thing- to some extent, there is always some art to it. It's another to dispense with analytical work entirely and just run a bunch of simulations and hope you hit the right conditions somewhere in there at random.

Well, even when you're doing it by analysis you'll still do some tweaking, yes, but I wouldn't trust such a control loop unless I had an analytical solution that showed good behavior not only throughout a normal run, but for oddball situations too.  If you know your stuff you can do this with pencil and paper, for God's sake.

   I know for direct fact that other of the new-space people don't know what they are doing. Carmack was on sci.space. <<something>> explaining why timing didn't matter and Windows RT was plenty good enough for the operating system - for his *gimbal loop* that probably needed to run at 120 hz+. He explained that they had done hundreds of simulations with random timing jitter and thus proved it. OY!

Windows RT?  There are combinations of microprocessors, data acquisition hardware, and operating systems that can be deterministic to less than a microsecond -- but I wouldn't "Windows" anything in a life-critical application.

  Even the Orion service module, which uses an old OMS pod engine and gimbal control, uses an analog system for the servo loop, partly because no one could build a discrete-sampled system fast enough. It's particularly bad when you take the gigantic OMS engine that used do push around the big old orbiter, and stick it to the back of the relatively tiny Orion CSM.

What bandwidth?  I can't speak to what's space-rated or not, but with today's parts you could easily close a 5kHz bandwidth loop using a general-purpose core (50kHz sampling rate), a bit more with a DSP core, and probably over 100kHz with an FPGA.

I've worked with some exceedingly technically conservative people who couldn't believe that digital loops could work comparably to analog, and in general my digital loops have held their own against their analog loops.  But that's digital loops done right vs. analog loops done right, and I'm not so enamored of digital for its own sake that I don't still consider (and sometimes use) analog loops where they seem warranted.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.


Advertise Here
Tags: