Slide rule use in space

[4ster]

I thought this would be a good place to ask this question.

Over dinner last night conversation veered into 1960's spacecraft and their nav computers. I mentioned that backup was a slide rule and my very smart, slightly older, civil engineering friend snorted and said there was no way a slide had the precision necessary to navigate a space craft. Sitting next to me was another smart, but younger aeronautical engineer that went to school in the post slide rule era so he was not backing me up.

After dinner, at home I ran across a posting that on a Gemini mission a crew member calculated a burn time faster with his slide rule than with the onboard computer. The post was hearsay and not something that I would consider evidence. Did they even have an on board computer on Gemini?

We all acknowledge that slide rules were aboard Apollo, Gemini and possibly Mercury spacecraft. The question is were they precise enough to calculate burn rates for orbital navigation and re-entry?

I am just a forester and was never very good with a slide rule. Their use was sun-setting about the time that I was in classes where they were necessary. Calculators were becoming common place.

[Maximilian Hohmann]

Hello!

(05-06-2016 01:59 PM)4ster Wrote:  ... but younger aeronautical engineer that went to school in the post slide rule era so he was not backing me up.

I'm not so young any more, but young enough to have studied aeronautical engineering without a slide rule (*), and more than willing to come to your rescue :-) They used slide rules - standard and special ones - on all space missions before the Shuttle (and I guess even then). The web is full of relevant sites, e.g. Aerospace related slide rules which contains this famous image of Buzz Aldrin and his slide rule onboard Apollo 11:



Best regards
Max


(*) About ten years after finishing university I treated myself to an ATPL (airline transport pilot license) and what surprise: The calculations during the theory classes and exams were all done on a slide rule...

[Accutron]

(05-06-2016 01:59 PM)4ster Wrote:  my very smart, slightly older, civil engineering friend snorted and said there was no way a slide had the precision necessary to navigate a space craft.

I guess that's why NASA hires aeronautical engineers for such things instead of civil engineers. The early space program was built with slide rules. Here's a quote from NASA engineer Bob Bobola:

"Computers were around, but they were great big in size. Most reports were handwritten, and a lot of the calculations – weight, center of gravity – were mostly done by hand using a slide rule. It's a wonder we were successful."

Faith 7 (Mercury-Atlas 9) lost altitude readings on the 20th orbit, and lost power to the automatic stabilization and control system on the 21st orbit. Gordon Cooper had to manually calculate everything with a Bulova Accutron Astronaut 214 wristwatch and a circa 1949 Keuffel & Esser slide rule, and pilot the capsule manually. It was the most accurate splashdown in the whole Mercury program, landing about four miles from the recovery ship.

[Didier Lachieze]

(05-06-2016 03:33 PM)Maximilian Hohmann Wrote:  The web is full of relevant sites, e.g. Aerospace related slide rules which contains this famous image of Buzz Aldrin and his slide rule onboard Apollo 11:

According to the NASA this picture was not taken on Apollo 11 but on-board Gemini 12: NASA photo number S66-62984.

[Maximilian Hohmann]

(05-06-2016 05:04 PM)Didier Lachieze Wrote:  According to the NASA this picture was not taken on Apollo 11 but on-board Gemini 12...

I think NASA is right... the window looks more like Gemini. This picture is shown on dozens of websites and all attribute it to Apollo 11. So much for "accurate information from the internet"!

[d b]

(05-06-2016 04:03 PM)Accutron Wrote:  Faith 7 (Mercury-Atlas 9) lost altitude readings on the 20th orbit, and lost power to the automatic stabilization and control system on the 21st orbit. Gordon Cooper had to manually calculate everything with a Bulova Accutron Astronaut 214 wristwatch and a circa 1949 Keuffel & Esser slide rule, and pilot the capsule manually. It was the most accurate splashdown in the whole Mercury program, landing about four miles from the recovery ship.

This is the most inspiring story I have heard in a while. Thanks.
When tales of explorers and adventurers end with "he left clicked to run the app and saved the day"; the human race will have went down the drain.

[rprosperi]

(05-06-2016 05:38 PM)Maximilian Hohmann Wrote:  I think NASA is right... the window looks more like Gemini. This picture is shown on dozens of websites and all attribute it to Apollo 11. So much for "accurate information from the internet"!

You beat me Max, I was ready to point out the window too. Totally unique identifier of any interior spacecraft shot, the "eyes" on the Gemini craft are always a dead giveaway. Best looking of all the spacecraft by far. If you don't know much about Project Gemini, read up on it, every mission was amazing stuff.

[4ster]

(05-06-2016 04:03 PM)Accutron Wrote:  

(05-06-2016 01:59 PM)4ster Wrote:  my very smart, slightly older, civil engineering friend snorted and said there was no way a slide had the precision necessary to navigate a space craft.

I guess that's why NASA hires aeronautical engineers for such things instead of civil engineers. The early space program was built with slide rules. Here's a quote from NASA engineer Bob Bobola:

"Computers were around, but they were great big in size. Most reports were handwritten, and a lot of the calculations – weight, center of gravity – were mostly done by hand using a slide rule. It's a wonder we were successful."

Faith 7 (Mercury-Atlas 9) lost altitude readings on the 20th orbit, and lost power to the automatic stabilization and control system on the 21st orbit. Gordon Cooper had to manually calculate everything with a Bulova Accutron Astronaut 214 wristwatch and a circa 1949 Keuffel & Esser slide rule, and pilot the capsule manually. It was the most accurate splashdown in the whole Mercury program, landing about four miles from the recovery ship.

I'll relay your observation about NASA's engineering preference to my civil engineering friend, which reminds me of a joke proving that God is a civil engineer...but I digress.

I looked into the Faith 7 flight, a truly inspiring story of a great pilot overcoming his craft's system failures, thanks for relating the incident. I'm not sure it proves my supposition about navigation using slide rules since ground support supplied the timing of the re-entry burn. I would assume that Cooper double checked the NASA math with his slide rule but from what I read the start of the burn was relayed via radio by Glen.

From the NASA history site:
Twenty-three minutes later Cooper came into contact with Glenn again, reporting himself in retroattitude, holding manually, and with checkoff list complete. Glenn gave the 10-second countdown, and Cooper, keeping his pitch down 34 degrees by his window reticle, shot his retrorockets manually on the "Mark!" Glenn reported: "Right on the old gazoo. . . . Dealer's choice on reentry here, [501] fly-by-wire or manual . . . It's been a real fine flight, Gordon. Real beautiful all the way. Have a cool reentry, will you."

Cooper timed his burn with his watch.

Except for re-entry and time spent on the far side of the moon, NASA was almost always in contact with their spacecraft. NASA probably generated all navigation data and relayed it to the spacecraft via radio on the Mercury missions. Which to me implies that the heavy lifting would have been done by computer. I did find that the Gemini space craft were the first with a "solid state computer" on board.

[Garth Wilson]

Howard Speegle of Diva Automation game me his permission to re-tell his story:

With your background, you might enjoy some aspects of my work on the Nimbus weather satellite. It had a 250 mW transmitter and our 85-foot dish with Maser amplifier could achieve autolock at -150 dbm at a range of 3000 miles.

However, the launch vehicle suffered an early burnout and the orbit was degraded, causing the satellite to be lost to the free world for three days. No one at NASA Goddard or the DEW line or any tracking stations around the world were able to locate any evidence that it existed. We scanned the skies continuously in every sort of random and geometric pattern for days, but no cigar.

Finally, I whipped out my trusty circular pocket slide rule and did a bit of jimjam combined with whazzamatazz and came up with a reasonable approximation of what the orbit would look like with a 10 second premature shutoff and suggested to my boss that they point the antenna in a certain direction at a certain time.

And lo!, it came to pass. He wanted to know where I had studied astrophysics and I didn't think he would appreciate knowing about my plastic slide rule so I simply shrugged it off.

A few weeks later, the ham club at the University of Alaska, down the road, timidly asked if we might have any interest in the telemetry tapes they had made of the first pass. A bunch of kids using a hand-pointed chicken wire parabola had made beautiful recordings of the entire pass and subsequent passes. They had outperformed the combined might of NASA and the millions upon millions of dollars of state of the art equipment we had. Kudos to them. I don't know whether we ever thanked them. Perhaps I should send this story to the university so they can add it to their list of accomplishments.

[brianddk]

(05-06-2016 04:03 PM)Accutron Wrote:  Gordon Cooper had to manually calculate everything with a Bulova Accutron Astronaut 214 wristwatch and a circa 1949 Keuffel & Esser slide rule, and pilot the capsule manually. It was the most accurate splashdown in the whole Mercury program, landing about four miles from the recovery ship.

Today I learned that wristwatches come with sliderules

[BruceH]

(05-06-2016 03:33 PM)Maximilian Hohmann Wrote:  ... this famous image of Buzz Aldrin and his slide rule ...

I thought for a minute he was smoking a pipe as well ... but it's the valve on the tank in the background.

[Massimo Gnerucci]

(05-10-2016 07:36 PM)brianddk Wrote:  Today I learned that wristwatches come with sliderules

Currently wearing this. :-)

[4ster]

Proof! With a dedicated navigational slide rule to boot.




Garth, that is a great story.

[StephenG1CMZ]

(05-10-2016 12:30 AM)Garth Wilson Wrote:  Howard Speegle of Diva Automation game me his permission to re-tell his story:

With your background, you might enjoy some aspects of my work on the Nimbus weather satellite. It had a 250 mW transmitter and our 85-foot dish with Maser amplifier could achieve autolock at -150 dbm at a range of 3000 miles.

However, the launch vehicle suffered an early burnout and the orbit was degraded, causing the satellite to be lost to the free world for three days. No one at NASA Goddard or the DEW line or any tracking stations around the world were able to locate any evidence that it existed. We scanned the skies continuously in every sort of random and geometric pattern for days, but no cigar.

Finally, I whipped out my trusty circular pocket slide rule and did a bit of jimjam combined with whazzamatazz and came up with a reasonable approximation of what the orbit would look like with a 10 second premature shutoff and suggested to my boss that they point the antenna in a certain direction at a certain time.

And lo!, it came to pass. He wanted to know where I had studied astrophysics and I didn't think he would appreciate knowing about my plastic slide rule so I simply shrugged it off.

A few weeks later, the ham club at the University of Alaska, down the road, timidly asked if we might have any interest in the telemetry tapes they had made of the first pass. A bunch of kids using a hand-pointed chicken wire parabola had made beautiful recordings of the entire pass and subsequent passes. They had outperformed the combined might of NASA and the millions upon millions of dollars of state of the art equipment we had. Kudos to them. I don't know whether we ever thanked them. Perhaps I should send this story to the university so they can add it to their list of accomplishments.

That is great achievement.
You might be interested to know that NASA now have some arrangement for calling on a group of radio hams when they want help with comms.
Eg
https://amsat-uk.org/2014/05/21/radio-ha...pacecraft/