Tuesday, July 21, 2015

Margaret Hamilton, Apollo flight software ninja

Margaret headed up the team at the MIT Draper Lab that wrote the software for the Apollo guidance computer. Vox.com has an interesting article about her and her software. The photo shows her standing next to the source code. The article elaborates on the technology of the day and how clever programming saved Apollo 11.

It also comments on the role women played in the early days of the software industry. When I started work, a lot of the programmers were women and some didn't even have a technical degree. I didn't know of any male programmers who didn't have one. Just an observation.


Monday, July 20, 2015

Saturn V, SA-667 continued

The top section of this model is basically complete, less recovery system (cord and 'chute). I could add a wrap to the bottom couple of inches, but I'm not sure how it will all hook together so I'll leave it off for now. Please ignore the fact that the LES is not perfectly straight.

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Just for kicks, I thought I'd make a bill of materials for this section (generally from the top down):

  1. 1/2" of 1/8" dowel.
  2. 3" of a Copperhead tube.
  3. Center disc left over from a centering ring.
  4. 9 paper wraps/components (Mostly from the AlaskaPaperModelWorks's stomp rocket plans).
  5. One tube from an AT DMS motor.
  6. One misc. tube that telescopes over the DMS tube (didn't have a long enough piece and the DMS was too small for the upper wraps when the bottom ones were sized to 3").
  7. One home made bulkhead for the DMS tube.
  8. One large screw eye.
  9. One random plywood disc to hold the screw eye (bulkhead hole was too big).
  10. 6 1/2" of 3" mailing tube.
  11. Home made ply rings to center the DMS tub in the 3" tube.
  12. Home made rings to center the 29mm motor mount in the DMS tube.
  13. 5" of LOC 29mm tube.
  14. Estes motor retainer.
  15. Two short pieces of Kevlar to form attachment points for the recovery harness.
  16. Masking tape, 5-minute epoxy, wood glue, Aleene's tacky glue, glue stick, double-sided clear tape.
That's a fair number of parts and a lot of effort for a rocket whose flight profile may be sub-optimal. I wondered if I should have skipped the induction stabilization and just build a scale Saturn V with lots of detail. Now, I don't think I'm up for another Saturn or Saturn-like object. At least for a while.

Sunday, July 19, 2015

Saturn V, SA-667 beginning

Overall, I still haven't decided what this thing will become, but I have started on parts of it. I have the upper body and have started on the motor mount. And I have the nose cone completed. To enhance the printed wraps, I found another paper rocket plan that included the launch tower. The LES motor is a tube from an AT Copperhead with a small wooden tip. In runs through the capsule into a wooden disc that was left over from a home made centering ring. The scale isn't perfect, but is good enough!

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Saturday, July 18, 2015

Launch Report 2015-6 (NARHAMS)

Location: NARHAMS, Mt. Airy
Weather: wind variable 0-10, cloudy becoming sunny, high in the mid 80's and humid
Total flights: Today - 10; YTD - 42
Total motors: Today - 11; YTD - 46
Motors by class YTD: MMX-2; B-1; C-13; D-2; E-9; F-11; G-7; H-1

Water rocket flights (not included in the totals above): 6


Last night, it looks like it would be cloudy with storms after two PM. This morning, I was disheartened when I found it was raining. However, checking the Mt. Airy weather it looked like the rain would move out and the afternoon would be sunny...and that's what happened!

The bad part was that the surrounding grass was un-mowed and this body doesn't like walking uphill in 3' grass. In the end, I kept most out of the grass and found everything except my V-2 cone that drifted over a far tree line. I found the body with my 18mm RMS case thanks to my wife's guidance. Phew!


My Flights:
  1. Hostile Projectiles V-2 on a D13-5 - High flight that separated on ejection. Lost the cone and, after much searching, found the body. The nice resin cone os OOP but I can find a suitable replacement.
  2. Estes SDI Satellite on a B6-4 - Nice flight and I even caught it in flight (photo is below).
  3. First Flight Hobbies Under Dawg on an D12-0/C11-3 - I angled the rod to keep it out of the grass and it weather cocked even more. But, the flight was great.
  4. F-in-Rocket on an F15-4 - Nice flight with recovery on mowed grass.
  5. AlaskaPaperRocketWorks Saturn V on a C11-3 - Nice but low flight.
  6. Upscale Cluster Bomb on a G74-6 - Nice flight. Big rockets are easier to spot in that grass :)
  7. Estes Snitch on a C6-0 - This one went much higher than its Quest counterpart.
  8. Quest SPEV Saucer on a C6-0 - Not as high, but still nice.
  9. Half ASStron Super-roc on a C6-3 - Despite it not having a 'chute or streamer, it sure drifts a lot. Once again, my lovely wife spotted it in the grass.
  10. Art Applewhite Stealth D5 on a C6-3 -  Nice!
Here's the mid-80's vintage SDI Satellite in flight. The rest of my photos are here.

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Friday, July 17, 2015

Saturn V, SA-666 rework

As I was pondering what to do with the SA-666's successor, I went back to read some of Dean Black's write-ups. I don't remember seeing this in his Apogee Newsletter article but I find that, while an air gap behind the CG results in induction stabilization, an air gap ahead of the CG retards it. D'OH, thats what I randomly decided to add to the SA-666. When it comes to rocket science, you just can't make stuff up. But hey, I never claimed to be a rocket scientist.

Soooo, I decided to resurrect this rocket and try again. The first thing I tried to do is find the transition wrap that I threw away when I invented the air gap transition. I didn't find it so a roughed out a new one (which lacks the nice detail...oh well).

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I also wrapped the damaged nozzles with some metal tape. In my experience, this stuff will protect the substrate, although the heat melts the glue so it tends to fall off. Oh well again...I only need it to stay on for one flight.

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Dean's latest reference design (updated from what's presented in the Apogee article) includes some added holes for long induction tubes. When I sized my air gap, I included the area of those holes in the main gap. There I went, making stuff up again. Anyway, I decided to cut some holes below the air gap. I don't know how this all plays out with the (hopeful) induction stabilization but it might help with any Krushnik problems. On the first flight, the rocket was stable (had a lot of coning, but generally went in an upward direction) but the altitude was a lot lower than expected. That could have been Krushnik or it could have been instant instability during coast. I wish it had been video taped, but I don't think it was.

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Random thoughts on the SA-667.  I still can't decide on the geometry of, or the material for, the internal, smaller induction tube. I am also thinking about making it a ring tail kind of like those used on water rockets. I just don't know. This build may not be finalized until after the MDRA August launch when the SA-666 will fly again.

Thursday, July 16, 2015

The nuclear age turns 70

Today marks the the 70th anniversary of the Trinity Test. You can visit the site, near Alamogordo, NM, on the first Saturday in April and October (April 4 and October 3, 2015).

Here is an animated .gif of the first 109 ms of the detonation. Credit: U.S. D.O.E.