[Spaceships] A slide rule will get you to the Moon . . . or will it?

[vicky_molokh]

Greetings, all!

I'm wondering, how serious is the title statement? Is it true that calculations necessary for space flight are mostly doable without computers at all? If so, how hard is it? How would 'retrotechy' TLs 8-10 look in terms of space exploration without computers?

Thanks in advance!

[giant.robot]

It kind of depends on how you interperet things. The math needed to design a rocket or navigate in space can be done by hand, it's tedious but it can be done. However building a rocket that will actually get you to the Moon is much more complicated. There's a lot of very low tolerance engineering involved in making rocket motor turbo pumps or building rocket stages that not only fit together but separate cleanly and reliably. While the math can be done on a slide rule the precision manufacturing is much more difficult. You'd probably want some sort of electro-mechanical controls on your lathes and mills. Do electro-mechanical controls on equipment fit into the theme of "slide rules get you to the Moon"? That's where it becomes a question of interpretation.

The Mercury, Gemini, and Apollo programs were as much a statement of the state of mechanical engineering and materials science as they were about rocket science. Jim Lovell was able to calculate a course correction for Apollo 13 while he and Earth were moving at thousands of miles per hour relative to one another having to hit a target only a few miles wide lest the capsule burn up in the atmosphere or skip off of it. That calculation is impressive enough but couple that with the amount of engineering that went into that capsule that managed to survive a catastrophic failure is absolutely mind boggling.

[Anthony]

Originally Posted by vicky_molokh

Greetings, all!

I'm wondering, how serious is the title statement? Is it true that calculations necessary for space flight are mostly doable without computers at all?

Doing orbital mechanics by hand is exceedingly tedious and in complex cases probably not practical, but for a relatively simple case such as earth to moon it's not too bad, particularly if you're willing to do mid-flight course correction and/or have an imperfectly optimized path.

[Purple Haze]

Nonsense of course. Large scale mechanical and electro mechanical computing dates from the 40's and mass produced entirely electronic computers from the ealy 50's.

Still it was good advertising: http://copland.udel.edu/~mm/sliderul...ettLEMflap.png

On the other hand, Mr. Spock apparently navigated the Enterprise with one you can see it in several episodes. The actual prop was every pilots "E-6B flight computer", so not realistic at all.

[sir_pudding]

Originally Posted by vicky_molokh

Is it true that calculations necessary for space flight are mostly doable without computers at all?!

Since we've had trouble with this before, what do you mean by "computer" in this context? If we go with the inclusive meaning that you've maintained in the past then no, of course not. The guy using the slide rule is a computer in that case. If we go by the most common modern usage of electronic microcomputers then yes, of course. The Apollo program predates the microcomputer revolution.

[Anthony]

A side note here: the accuracy required for single-burn courses (i.e. you run the rocket once at the start, then coast) or two-burn (run the rocket at start and end) is probably not possible for human control; an Earth-Mars course with aerobraking requires something like 1/100,000,000 accuracy. However, if you have a bit more delta-V usable during the trip, course correction should be within human limits.

[vicky_molokh]

Sir, I guess I should've been more clear. I meant not using a device that performs computations. (I see the slide rule as a device that essentially stores and displays reference tables, but relies on the user to perform actual computations.)

[sir_pudding]

Originally Posted by vicky_molokh

Sir, I guess I should've been more clear. I meant not using a device that performs computations. (I see the slide rule as a device that essentially stores and displays reference tables, but relies on the user to perform actual computations.)

That user was called a "computer". If you are going to consider an automatic transmission as a computer then surely you can count the much more sophisticated mechanical and electric computational devices that have been used before microcomputers. There isn't a problem with retro-tech orbital mechanics and astrogation using available technology from TL5 on, IMO. There certainly isn't at early TL7, since it worked in real life!

[Snoman314]

Bear in mind that Apollo incorporated one of the worlds first modern-style IC chip based computers, using programming that at a fundamental level used the some of the same principals as modern computers (multi-tasking, virtual machines etc)

[teviet]

Originally Posted by Anthony

A side note here: the accuracy required for single-burn courses (i.e. you run the rocket once at the start, then coast) or two-burn (run the rocket at start and end) is probably not possible for human control; an Earth-Mars course with aerobraking requires something like 1/100,000,000 accuracy. However, if you have a bit more delta-V usable during the trip, course correction should be within human limits.

Yes, the required precision is a major factor in whether you can reasonably do it by hand. For a real retrotech space opera feel, ditch the computers but keep the fusion torchdrives. With enough delta-v and good acceleration you can just fly by the seat of your pants.

Edit: Hmm, but Vicky said TL8-10, not 10^, nevermind.

TeV