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Comment by ponker | Hacker News Reader

They didn't even spin something 350 times before launching it out of the solar system?

It's remarkable to see people doing the usual "well this could obviously have been avoided by..." on something still functioning after 43 years and almost 12 billion miles from home in the most hazardous environment known to humans.

They did an absolutely amazing job and I take it as a given that this was not some novice mistake.

If the actuator broke down the 351st time, would you've commented 'they didn't even spin something 400 times...'? What would be a number you'd be comfortable with instead?

I would have thought they would run every part until it died so they know roughly what it's lifespan is. It's good if the parts lifespan is twice as long as you need. However, it's even better if you could make it four times the amount you think you need, as long as it isn't horribly expensive.

I would tend to assume they've thought of that though, and stuck with this part for reasons. Maybe there werent other space-ready alternatives or something.

I don't think any of us are in a position to be too critical of the engineering done for the Voyager probes. The number of machines running continuously for longer than I've been alive with no maintenance is pretty short; the number of them out past the orbit of Pluto even smaller.

This is actually a fairly egregious oversight, but it is good to know they fixed it.

It's impossible with current technology to make a vacuum as good as outer space on Earth, which hampers testing of components in realistic conditions. See also Galileo's antenna.

When you are weight constrained the way a space probe is, every factor of safety above the bare minimum is horribly expensive. With no risk to human life and a skilled team of engineers on the ground, the cost of further risk reduction easily may not be worth it.

Maybe the expected number of times it would be expected to spin in space (or twice that to make sure it's working)

The initial Voyager program already ended, and they are now in an "extended" mission.

640k

Maybe as many times as needed to do the minimal in-solar-system observations that were planned well in advance?

On the other hand, if they had to budget for a second copy of everything in advance they may have never gotten to launch. Asking for the funding after already having good success behind them is likely a lot easier.

Accelerated simulation of the effects of years in the vacuum and temperature of outer space on lubricants is non-trivial.

But a duplicate of the actuator failed in a lab on Earth after almost exactly as many turns as the actuator in space lasted -- that's how they determined the cause of the spacecraft's going offline.

True, but that confirmed the test run in space, not the other way around. It may have be hard to know in advance if 348 failures on Earth is representative of space, especially because it wouldn’t just be that one system. It would have been lots of parts built in to system working together.

Original mission for Voyager 2 was Jupiter and Saturn fly-bys which was mostly a success. The idea is to engineer parts to survive the mission and maybe go a bit further if you aren't at a point of diminishing returns in regards to cost. If it costs $1000 for a 10% gain in life of part, maybe go for it. $1M for 10%? Maybe not. Additionally, gamma radiation can do some weird things to materials and can effect things differently depending on dose rate. Lubricants can increase in viscosity and acidity under gamma. Radiation effects on spacecraft was not as big of a deal back then. Missions were short and electronics weren't small enough to have noticeable radiation effects.

What you say is just common sense but as you can see from the downvotes, average people do not like smart people. And the exact same thing happened before the launch, I bet. But the exceptional engineer was simply “downvoted”.

Things are tested all the time in factories. For how long? Till destruction.

One of the standard examples of common sense is “everything that goes up must come down”.

When it comes to space missions, common sense starts bad and rapidly gets worse — there is no down, there is no “now”, metals can contact-weld without any supply of energy, exposed fluids boil until they freeze, radiation pressure is relevant, ionising radiation doses can be enough to break things, impact damage is radically different, launch times are prescribed by orbital dynamics, engines are more efficient when they are moving faster, fuel use is exponential with regard to change in velocity and nothing to do with distance, and the launch mass is heavily constrained. And that’s just the stuff I know from following Scott Manley and similar on YouTube — I’m a very long way from being a rocket engineer.

Is that your justification for not testing the actuator? Space is hard, let's not test things?

If you want to launch on the Grand Tour, your launch options are the 1970s and the 2140s.

You hit the date, you test what you can, within that constraint.

(They were also heavily budget limited, and I’m sure everyone here has an example of a project which became more expensive because someone decided they “couldn’t afford testing”).

Even then, even despite people who probably have PhDs in specific engineering topics I can’t even name, half the time you can’t even tell what’s important to test vs “it’s common sense this will work fine for a thousand cycles” — hence the long list of missions which failed catastrophically.

It is rocket science.

Ah, but of course you are one of The Smart People whereas we plebians (and the NASA scientists who designed and launched the probe) are merely average.

Thank you! now you get it!

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