Space Instrumentation

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Magnus
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Space Instrumentation

#1 Post by Magnus » Sat Jan 19, 2019 12:08 pm

Rocket Science isn't rocket science.

I worked on instrumentation for the James Webb Space Telescope. The instrumentation was fairly straightforward, although some of the specs were pretty rigid. Cleanroom conditions at all times. There were some things I hadn't thought of, such as no "blind" holes in panels, &c. There are NO trapped areas which might contain air, which will leak out in vacuum conditions and trundle about with the instrument in space deteriorating the "in vacuuo" image quality. You want to put a bolt in there? You drill right through the panel so the air escapes before the telescope reaches orbit. Fun challenges.

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Re: Space Instrumentation

#2 Post by Cacophonix » Sat Jan 19, 2019 6:21 pm

The whole concept of using differential gas pressure in spaceflight reminded me of this little gem!
About 257 seconds into the flight, the second stage cut off, and the rocket entered a coast phase to apogee. Immediately after cut-off, the second stage attitude control system was pressurised. During the coast the correct orientation for third stage separation was maintained by means of the attitude control system. Towards the end of the coast period, the third stage was spun up to a rate of 3 hertz (180 rpm) by means of six Imp rockets.Five seconds later, the third stage separated, and following ten more seconds of coasting, it ignited. The third stage was a Waxwing solid rocket motor, which burned for 55 seconds.

Just over a minute after the third stage had burned out, the payload was released, and gas generators were used to push the spacecraft and spent upper stage apart. The delay between burnout and separation was intended to reduce the risk of recontact between the upper stage and payload due to residual thrust. Despite this, following spacecraft separation on the R3 launch, the upper stage collided with the Prospero satellite, damaging one of the spacecraft's communications antennae; however the spacecraft was still able to successfully complete its mission .On the R3 launch, the ascent took 710 seconds (11.8 min) from liftoff to spacecraft separation.
https://en.wikipedia.org/wiki/Black_Arrow



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Re: Space Instrumentation

#3 Post by Slasher » Sun Jan 20, 2019 3:14 pm

I don't know much about instrumentation, but the mathematics involved in getting Apollo XI to the Moon and back was staggering to say the least. Apart from the usual laws of Newt, Bert Einstein was thrown in as well as a pinch of Quantum mechanics. All done with blackboards, pencils, paper, slide rules, and computers that were slightly more than pocket calculators. Man...those boffins were absolute bloody geniuses figuring out stuff never before attempted. I marvel at that.

It's like as if Queen Victoria had stated "before this decade is out, the goal of this country is to transmit moving pictures of the far flung reaches of the Empire, and receive them safely in Britain."

And the eggheads of that era, 9 years later, went and built a UHF satellite colour telly!

BTW, did you know that the Space Shuttle was originally built to commerial airline specs? Yep +2.5G/-1.0G and all that sh!t. Didn't believe a word when I first read about it in the early 80s. Thought it was a pud pull.
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Re: Space Instrumentation

#4 Post by OFSO » Thu Jan 24, 2019 7:58 pm

I know of at least one mission where after payload ejection a 'few' CCS of fuel and oxidiser ignited (relit) in the chamber and the third stage lunged forward and gave the payload a mighty whack. This is why ullage motors are fitted. The majority of ejection systems I remember were massive springs between payload and vehicle, held in compression until a pyrotechnic device cut the wire. Why ? Go for simplicity, that's why. Another marvellous device for despinning a cylindrical spacecraft consisted of two cables wrapped around the payload, with weights on the ends, all held in place by pyrotechnic cutters. Execute execute execute, the pyro cutters went off, the cables unwrapped, slowing the spacecraft as they did so, and being loose-tethered at the ends, unhooked and disappeared into 'space' in opposite directions to mystify aliens who will find them in a few years time.

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Re: Space Instrumentation

#5 Post by OFSO » Mon Apr 15, 2019 6:35 pm

Interesting questions on TOP regarding the failure of the British-built descent motor on the Israeli lunar probe. Characteristics of thermal dissipation in vacuum are very well known and suggestions that there was uncertainty about the effects of heat soak are surely misplaced.

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Re: Space Instrumentation

#6 Post by Boac » Mon Apr 15, 2019 7:14 pm

It is surely obvious that the Israelis screwed up and cut too much off the end of the nozzle?

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Re: Space Instrumentation

#7 Post by ian16th » Mon Apr 15, 2019 8:19 pm

Slasher wrote:
Sun Jan 20, 2019 3:14 pm
All done with blackboards, pencils, paper, slide rules, and computers that were slightly more than pocket calculators.
The main computer power at NASA in the 60's was a whole lot of IBM 1800 Data Acquisition & Control Systems, plus a few S/360's.
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Re: Space Instrumentation

#8 Post by OFSO » Tue Apr 16, 2019 3:05 pm

When I arrived at ESOC the Big God was an IBM1800. Could its successor have been a 360 ? Hard to remember fifty years later.....

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Re: Space Instrumentation

#9 Post by ian16th » Tue Apr 16, 2019 4:35 pm

OFSO wrote:
Tue Apr 16, 2019 3:05 pm
When I arrived at ESOC the Big God was an IBM1800. Could its successor have been a 360 ? Hard to remember fifty years later.....
The 1800 and S/360 different architectures, but were both built with the same technology.

There was never an IBM successor to the 1800, or the 1130 on which the 1800 was based.

That market was left to DEC, to so that IBM could claim they didn't monopolise the market.
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