Would we have got to the moon with no semiconductors?

[Uncle Bulgaria]

BBC World Service produced the fabulous '13 Minutes To The Moon' series about Apollo 11, including an episode on the rope memory and the computer system. Now there's a second series on Apollo 13, as the first was so well received. I was delighted to find there's a lot of detail and extra interviews. The conceit being that they drip-feed the listener enough information throughout the series so that in the final episode the titular '13 minutes' of radio traffic from descent to landing are played without commentary because one can by then follow the conversation in real time.

[Electronpusher0]

Originally Posted by Richard_FM

I remember it was mentioned when I was on a guided tour of the Air & Space Museum in Washington, the computer on board the lunar module failed & the astronauts had to manually operate the rockets to bring it down.

As I understand it the computer twice gave an alarm indicating that one of the processes had run out of time. The computer acheived multi tasking by allocating each process a slice of time to complete its action.
The docking process needed to redock the moon lander crew capsule with the command module was switched on in error.
Ground control decided it was safe to ignore the error and continue the landing.
Neil Armstrong did overide the landing computer because the programmed landing site was boulder strewn, he took over and guided the lander to a clear area, nearly running of fuel in the process.

Peter

[Bazz4CQJ]

Peter is correct and the question of the computer "failing" on Apollo11 is potentially a very misleading one. Let's start by saying that on the next flight, and all the subsequent ones, it did just what they intended it to do.

Investigation of what went wrong with the computer during Apollo 11 revealed a number of problems, mainly about how three different radar systems where configured, all interacting with the computer at the same time and so over-loaded it. The problem was sorted out before the next mission flew just a few months later, Apollo 12 making a pinpoint landing very close to an old 'Surveyor' spacecraft which landed some years earlier. They were able to walk over to it and cut bits off which were brought back for analysis.

I don't believe the flights would have possible with valve equipment.

B

[M0FYA Andy]

Surely a more relevant and fundamental question is "If solid-state technology hadn't been invented/developed at the time it was, how would valve technology have developed during the fifties and sixties and subsequently?"

Andy

[ms660]

No problem getting to the moon without semiconductors....just point, shoot and steer.....DOA.

Lawrence.

[Radio Wrangler]

Yes, getting back is the defining achievement.

There's an old saying, "A good landing is any one you can walk away from. A very good landing is one where you can use the aircraft again" We'd have to modify that to swim for the Apollo missions.

There have actually been volunteers for a one-way mission to Mars. I assume they would want to land softly and to be able to look at a few rocks.

In the popular press, mass has to be expressed in London buses, volume in Olympic swimming pools. Maybe computing power ought to be expressed in Lunar Landers?

David

[Richard_FM]

Large areas seem to be measured in the size of Wales for some reason, as a few stand up comedians have pointed out.

Large explosions & acts of nature seem to be in atomic bombs, usually the Hiroshima one.

[paulsherwin]

Back on topic please.

[rontech]

Originally Posted by M0FYA Andy

Surely a more relevant and fundamental question is "If solid-state technology hadn't been invented/developed at the time it was, how would valve technology have developed during the fifties and sixties and subsequently?"

Andy

I have thought about development of valve technology from time to time. Given the size of vacuum tubes that were developed for TV. Maybe large numbers of diodes or triodes could have been assembled within one big tube. Then used for logic gates etc. The valve base may have to be unmanageably large though.

A lot of heater current needed too I imagine.

[Buzby123]

... A lot of heater current needed too I imagine ...

I seem to remember years ago in some electronics magazine, a description of a cathode that emitted electrons without needing heat.

The emitting surface used what would now be called nano-technology, and consisted of millions of tiny spikes.

I'd be pleased if anyone can confirm I'm not imagining this.

Cheers,

Buzby

[Radio Wrangler]

Confirmed!

Never came to anything, though... at least nothing I heard of.

David

[Al (astral highway)]

Originally Posted by Oldcodger

RE#9- I remember seeing a document in the late 60's where a Russian plane was forced down and on investigation it was discovered that the electronics were valve based.

Have a look at photos here. I think valve technology went on far longer in the Soviet bloc, but in UK issue kit too.

This is an MOD issue VHF/UHF amplifier. It looks 80's to me.

It contains at least one nuvistor, several transistors and a valve that I can't identity without taking the unit apart.

It is hugely ruggedised and I wouldn't be surprised if it was for use in fighter planes.

As far as the original question, it's an interesting one.

The will to do it, within the context of the Soviet/US competition for supremacy and the reasons why that was so pronounced - well, that wouldn't have gone away if semiconductors weren't on the scene.

I have often wondered how systems that simply couldn't be allowed to fail (e.g, mechanical switches for various commands) were made fail-proof, even if it was by replication.

[Bazz4CQJ]

Originally Posted by rontech

I have thought about development of valve technology from time to time. Given the size of vacuum tubes that were developed for TV. Maybe large numbers of diodes or triodes could have been assembled within one big tube. Then used for logic gates etc. The valve base may have to be unmanageably large though. A lot of heater current needed too I imagine.

It's important to recall that semiconductors and even IC's were around well before Apollo. Were there any valves in any of the early ICBM's like Atlas and Titan, which preceded Apollo by some years? Were there any valves in the Mercury or Gemini spacecraft? I don't think so.

B

[Buzby123]

Originally Posted by Radio Wrangler

Confirmed! Never came to anything, though...

It probably wasn't developed because valve stuff was long out of fashion by then.

But if there was no alternative, it could have been a solution to the heat problem.

So by now we would have low power, high speed, minature valve-based circuits, built using layer technology, a bit like ICs.

I don't know how small a 'thermionic' gate can be built, I don't know the maths, but I'm sure if it was the only option it would have been done.

Cheers,

Buzby

[broadgage]

It seems reasonable to suppose that without semiconductors, that valve technology would have improved.
I suspect that such improvements would have relatively minor however. By the 1950s valves were a mature technology with only limited opportunities for improvements.
Cheaper ? almost certainly due to semi automated mass production.
More reliable ? almost certainly due to better quality control.
Smaller, yes but only up to a point due to electrode spacing and heat dissipation requirements.
Lower power consumption, probably, though the later battery valve receivers were already very good in this respect.
Some TV valves were already as small as was sensible, and some types arguably TOO small and prone to a short life.

As has already been said, the Russian military used sub miniature wire ended valves.
Without semiconductors, this sort of valve would probably have been widely used in consumer electronics.
If sufficiently long lasting and reliable they could be soldered into place, thereby avoiding the cost/space/weight penalty of valve holders, and eliminating one cause of faults.

I recall a late relative who used a very compact valve hearing aid, HT was 22.5 volts and LT 1.5 volts from a single C cell. I think that it used wire ended valves. Shirt pocket sized.

Another snag is you only get NPN valves.

[ms660]

If they had carried on the development, the valve technology would have hit the buffers, just like propeller, internal combustion engine, jet engine and steam piston power technologies would have done/will do, it's not rocket science (scooze pun)

Lawrence.

[G6Tanuki]

For space applications, cooling is a big problem; in zero gravity there are no convection-currents, so everything that generates much heat has to be cooled by radiation or conduction (or fans).

Semiconductors - lacking heaters - obviously have an advantage here for space applications; likewise the 'power budget' of spacecraft is often rather tight so not-needing-heaters is a big benefit.

Remember though that the first Russian Sputnik beacon transmitter was valve-based, and ran on batteries. The US's catch-up satellite launched a few months later used transistors....

Semiconductors-in-space used to have one significant issue - particularly with memory-devices there was an issue with high-energy subatomic-particles which - if they passed through a semiconductor memory-cell - could release enough electrons to 'flip' the cell's state! There could be advantages to using old-style ferrite core-memory.

[Keith]

Couldn't orbital calculations have been done using valve analogue computers?

[Buzby123]

Originally Posted by broadgage

... I suspect that such improvements would have relatively minor however...

I don't agree. If valve tech had advanced at the same rate as, say, LED tech, what would we have now ?.

Just look at what an LED could do in 1975, glow a dim red !. Now they can illuminate football pitches, replace lasers and CRTs, and cost next to nothing.

Thinking that valve progress would be limited doesn't take into account new manufacturing and material technologies.

Look at circuit manufacture. From tag-strips to single-sided SRBP took 100 years. From there to 64-layer boards took 50 years.

If valve tech was re-engineered to be PCB based, you could imagine a PCB-like structure, with multi-layers of 'valve' elements, using cold-emitters, and printed interconnects.

In fact, in a world devoid of semiconductors, I can't even imagine what technology would take its place, but I know something would.

Cheers,

Buzby