I was just reading the pale blue dot and he mentions that Voyager 2’s scan platform jammed after its encounter with Saturn.
Voyager 2 emerged from behind Saturn (as seen from the Earth) in August 1981. The scan platform had been moving feverishly—pointing here and there among the rings, moons, and the planet itself during the all-too-brief moments of close approach. Suddenly, the platform jammed. A stuck scan platform is a maddening predicament: knowing that the spacecraft is flying past wonders that have never been witnessed, that we will not see again for years or decades, and the incurious spacecraft staring fixedly off into space, ignoring everything.
The scan platform is driven by actuators containing gear trains. So first the JPL engineers ran an identical copy of a flight actuator in a simulated mission. This actuator failed after 348 turns; the actuator on the spacecraft had failed after 352 turns. The problem turned out to be a lubrication failure. Good to know, but what to do about it? Plainly, it would be impossible to overtake Voyager with an oilcan.
The engineers wondered whether they could restart the failed actuator by alternate heating and cooling; maybe the resulting thermal stresses would induce the components of the actuator to expand and contract at different rates and unjam the system. They tested this notion with specially manufactured actuators in the laboratory, and then jubilantly found that in this way they could start the scan platform up again in space. Project personnel also devised ways to diagnose any additional trend toward actuator failure early enough to work around the problem. Thereafter, Voyager 2’s scan platform worked perfectly. All the pictures taken in the Uranus and Neptune systems owe their existence to this work. The engineers had saved the day again.
Our hacks are nothing compared to the hacks of these old school nasa programmers :)
Our hacks are nothing compared to the hacks of these old school nasa programmers :)
The amazing thing (to me) is that they developed the Voyager spacecraft in an era when space flight wasn't hugely popular and the budgets at NASA were being cut regularly. NASA went from a peak of $6bn a year in the mid-sixties under Johnson to almost half that under Ford and Nixon. The engineers were well-respected and they clearly felt the work was important, but they weren't particularly well paid. They did this for the love and the science.
It's great, but hardly amazing. Most academic research is done by underpaid PhD and postdoc students for the love of science, and most of that is far less glamorous than SPACE.
> Most academic research is done by underpaid PhD and postdoc students for the love of science
I’d hardly call the graduate papers coming out of academia equivalent to the level of innovation & creativity of what the engineers above described. Perhaps they’re both underpaid, but one is certainly more amazing. Hardly the same.
You should read Rhodes’ “The Making of the Atomic Bomb” if you want to understand what incredible engineering feats academic scientists are capable of — when the people are tightly focused on achieving a single goal. You should also read Rhodes’ book if you want to understand why unguided fundamental scientific research itself is so critical, even when it doesn’t immediately seem useful to you: without the discoveries of science, nuclear fission wouldn’t have been understood. (Of course, many will disagree that the development atomic bomb is a good outcome, but that’s a very different conversation.)
That's a pretty amazing comment to me. Perhaps I am biased because of all the blood sweat tears and life I spent publishing papers in academia. Generally, with the exception of certain low quality publication venues, certain fringe areas of humanities, and of course review papers, each academic paper is a new contribution to science that has never been made before. Heating and cooling something to unjam it? That's been done since the dawn of modern engineering. A neat story (and I mean it), but hardly an astounding level of innovation and creativity.
Are you seriously claiming almost every academic paper in a prestigious journal demonstrates more innovation and creativity than that displayed by the deployment of the Voyager spacecraft? I strongly disagree.
Remember also that a large fraction if not a majority of the Voyager team almost certainly had PhDs or even came from academia. I think we can appreciate innovation and creativity everywhere without having to make it into a genital measuring contest.
I was responding to a comment about a story that was specifically about the unjamming by heating/cooling; a phenomenon which everyone above the age of six knows about. My comment was not a genital measuring context, nor did it have anything to do with the innovation and creativity displayed by the deployment of the Voyager space craft.
This is clearly about more than just unjamming a part, but the work that was put into building the probe, sending it to the edge of the solar system, and the fact that it's still functional today.
The person I was replying to was very clearly not calling the result itself amazing, but the fact that it was achieved by people whose budgets had been cut in half and who were not well paid.
I believe the aspect of beauty and glamor is a matter of taste and hence very subjective. Maybe some projects may turn out to be less influential, but nevertheless it appeals to a particular community.
You can't just look at the NASA budget. Defense spending was also a huge part of our activities in space.
My grandfather built satellites at Lockheed in Sunnyvale all through the 60s and 70s and it was a glorious time for him. For reasons that I never quite understood, he hated Reagan for "destroying the industry" in the 80s (by which time he was in Denver at MM).
In the 60s, they were pushing to get things out and accepted risk levels that today we would consider intolerable.
Today we've developed a cost-plus contracting approach plus insane safety and success standards that mean it is almost impossible to actually get anything done. With one notable exception - SpaceX.
Just throwing money into Boeing and Lockheed these days would generate profits for them, but not a lot of science for us. We need to change culture as well.
I wish we could spend money on NASA like we did in the 1970’s
I absolutely agree. It's far worse now. And, not at all coincidently, NASA is doing much less science now. A return to the 70s budget by GDP would be good, but a return to the 60s budget by GDP would be even better.
I don't see anything on that page given as a percentage of GDP, just percentage of federal budget, and inflation adjusted. And while the inflation adjusted numbers have been on the decrease since the early 90s (when shuttle production ramped down) they are still a little higher than they were in the 70s.
I'd love to see NASA's budget increased, but not now - it would just get funneled into dead-end pork projects like SLS. I'd much rather wait till Starship is successfully operating (New Glenn would be a plus), and it is political viable to end the SLS entirely, and redirect all that money and some into missions (both science and exploration) rather than hardware development.
Or to put it another way, it isn't worth it to me to spend 1960's era money if we are only going to get 1960's era results. If we ever want to move on to bigger things in space, like colonization, we can't just throw money at the problem, we need to find ways to bring the cost down first.
Check out Zarch on the Acorn Archimedes. https://www.youtube.com/watch?v=MNXypBxNGMo It's an awesome 3D game from 1987 (with truly awful sound). That was made 6 years before Second Reality, on a RISC-based computer. It's incredible.
When I saw that one I had never seen anything so smoothly animated before that demo in my life. I think my brief exposure to the demoscene spoiled me, because I now can't stand the slightest graphics hiccup in anything.
I do not believe that is accurate and I also find it disrespectful to call engineers 'hackers'. Most people today that refer to themselves has 'hackers' are also not (also get off my lawn).
It looks like they spent a lot of resources to fix it. In our current business environment, the engineers will be moved to another more visible/successful project and this one will be written off.
It has become commonplace to solve hardware problems with software. But many times it is not for heroic reasons, it's because hardware is cost-reduced.
I'm not sure I'd agree with that at all. On the surface of this planet software is used to simulate hardware as it's much quicker to iterate on a design.
In space, however, you can only run the hardware in it's destined environment once. Software is critical to the design process regardless of the HW costs.
A former coworker/friend was telling me similar stories of his uncle working on missile guidance analog computers from the 1970s. He referred to it as "proper engineering"
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.
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 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.
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.
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.
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.
I don't think the Register's headline is very accurate. The probe itself remained online, and there was plenty of radio communication happening during that period; it was just one-way, from Voyager 2 to Earth. From NASA's press release:
> The call to Voyager 2 was a test of new hardware recently installed on Deep Space Station 43, the only dish in the world that can send commands to Voyager 2. ... Since the dish went offline, mission operators have been able to receive health updates and science data from Voyager 2, but they haven't been able to send commands to the far-flung probe, which has traveled billions of miles from Earth since its 1977 launch.
That's funny, I had exactly the opposite reaction. Almost 20 light hours sounds far for something we basically strapped on the top of a big firecracker, which probably provided propulsion for at most a few dozen minutes... The fact that it was even possible to make that thing fly over several planets before exiting the orbital plane on a predictable course, and that one can still communicate with it as it exits the heliosphere is truly awe inspiring to me.
Interstellar travel, unless there's a revolution in propulsion, is unlikely to happen I think. I'm sure that at some point they'll send up another probe with more fuel to go out faster, but it's not going to be revolutionary.
Project Orion is kind of ludicrously inefficient, making it largely useless for interstellar travel. A nuclear powered ION engine can achieve a much higher exhaust velocity and replace that giant pusher plate with useful propellant.
It’s one of those designs that trades something considered largely meaningless, total engine weight, for something considered far more important exhaust velocity. This always ends up being a far worse trade off than simple models suggest.
PS: It could have very high acceleration before running out of fuel, but if the trip is going to take decades either way that’s not very important.
As long as we are talking hypothetical designs, you can use spent nuclear fuel as reaction mass an ION engine just fine. That said, weight wise it’s fairly trivial so you could just eject it.
Project Orion is detonating nuclear weapons which consist of far more than just fuel, they also need high explosives etc, however much of the fuels energy is wasted both from low yield bombs being less efficient but also simply radiating energy in all directions. Nuclear powered ION engines however would be ejecting far more of their reaction mass of say xenon per KG of fuel that leftover fuel is basically irrelevant. In other words it’s a more efficient nuclear reaction, a vastly more efficient engine, and a much lower mass fraction spent on the physical engine.
This gets more extreme when you consider a crewed mission would need lots of power during the trip so they would want/need to build redundant nuclear reactors anyway.
> Nuclear powered ION engines however would be ejecting far more of their reaction mass of say xenon per KG of fuel that leftover fuel is basically irrelevant.
Wait, if that is true, then the ION engine has a lower ISP than direct explosions, not higher. Unless the reactor is orders of magnitude more efficient than the bombs.
Nuclear ION reactors are orders of magnitude more efficient. I think you’re being confused by not actually modeling what’s going on.
Smaller nuclear detonations are less efficient in that they directly liberate less energy from their fuel. A nuclear explosion in space also radiates most of it’s energy as X-Rays which on earth you heat the atmosphere but in space mostly just do nothing. So their directly turning less nuclear energy into motion. Further, a smaller percentage of that force is then collected by the pusher plate compared to the Bell nozzle at the bottom of a traditional rocket. https://en.wikipedia.org/wiki/Bell_nozzle
Now as nuclear is so much more energy dense than chemical energy on paper they look better. But compare ISP’s and you see just how much energy is lost.
All of that can be simplified by just looking at ION thrusters ISP and vs the ISP of hypothetical Orion rockets. At that point it’s just a question of what percentage of mass is reaction mass vs the reactor + fuel and it turns out you can get reaction mass well over 80% making at least 60% more efficient before considering the pusher plate assembly’s mass vs physical ION engine’s mass.
PS: And that’s when looking at existing ION engine designs. Hypothetically, you could eject matter at a large fraction of C using energy giving orders of magnitude higher ISP, at the cost of lower energy efficiency etc.
Check out Hardtack Teak. It was an exo-atmospheric nuclear test above Johnston Atoll. The blast was visible from Honolulu and a large glowing red cloud drifted over the island chain all the way from Johnston Atoll. There are areas of the zone underneath the explosion which are still hot to this day. And that was just one of the tests that went right. There were plenty of failures too, both in atmosphere and on the launchpad, which spread nuclear material and toxic fuel all over the place. High-altitude nuclear explosions are definitely a threat to humanity, no doubt about it.
Maybe. Personally, I would want to see A LOT of math and paperwork first before I listen to anyone who uses "perfectly safe" and "nuclear explosion" in the same sentence. I'm still hoping we can figure out some other form of space travel which doesn't involve really, really, really big explosions.
Micro craft with light sails propelled by lasers have been discussed quite a bit. My favourite instance of it is in Charlie Stross's novel Accelerando.
I would guess that radioactive particles on the surface would be different that radioactive bombardment from space. You could shield your shelter from space, but if the soil had radioactive particles in it, then you couldn’t bring it in your shelter. For that matter, you would also have to shield the floor, or at least remove a layer of soil. You might have to do that anyway to build a foundation.
If it isn’t obvious, I don’t know what I am talking about.
Lets imagine... hypothetically [1] that we could design a new kind of space oriented machines, sort of a "spatial server" or a "telephone repeater", that could be left in Pluto (or an asteroid, or orbiting Saturn, whatever...), and be designed to take this weak signals, amplify it, and resend it to the earth
Would this help to increase the range of what discover can report and... hum, discover?
Would help us to have the info in two months instead in eight? (maybe splitting in a multipart message and broadcasting in several threads and different frequency bands at the same time or so?).
or would be basically useless?
Could be used to start a exploring outer web that would be improved with each new launching as other countries connect to it?
[1] I don't know how realistic, or technically difficult would be. Is an idea idea that just occurred to me
Its useless. Most of the time Earth is closer to the Voyager spacecraft than Pluto (or Saturn or...) is! In addition, we can build and maintain much better equipment here on Earth than we can ship to Pluto.
If you wanted to do this "for real", the better option is to send a train of repeaters after the Voyager spacecraft in roughly the same flightpath. More effective, and vastly easier.
You'd need a good planetary alignment to get the huge boost that voyager got. But not to get on the trajectory. Your repeater would get further and further from voyager, but not as quickly as earth is.
And yes, the repeater can both do tx and rx repeating.
That said, I'd expect Earth based (including earth based orbit) solutions to outperform at a lower cost for a long long time.
Probably not. It takes Megawats of power to ensure the small antenna on the proves gets the signal, it's not feasible to put such a thing on a spacecraft. Add to this the limited usefull life of Voyager's RTG power source (after 40 years, half the plutonium have already decayed) and we can conclude that this is not a good idea.
Carl Sagan mentions this possibility in Pale Blue Dot, concluding that such a mission's budget could be better utilized for other projects. For the following reasons:
1) Voyagers have turned off most of their instruments due to their diminishing power sources
2) Voyagers are moving away with speeds that are hard to match by even contemporary launches thanks to their gravitational assist trajectories.
I like it. You'd need (many) more than one. Pluto has an orbit of 248 years. Kind of like putting your wifi router on a train track on your property line and sharing with your neighbours.
Perhaps on a bunch of objects at Lagrange points [0]?
That's exactly how the Soviets pulled off the geopolitical coup of broadcasting images from the dark side of the moon back to earth. They pulled it off first, because they were clever about it.
What you are proposing will absolutely work. Imagine a self-routing datagram trying to get closer to its destination at each step. In fact, that's exactly how the Internet is designed. Self-healing, self-routing, best-effort. Chop messages up into little pieces, and send them off to their destination, and hope for the best that they'll be reassembled correctly at the destination.
Richard Stephenson works in
operations at the site of the antenna mentioned and sometimes gives some "behind the scenes" views, worth a follow https://twitter.com/nascom1
I know it's the year 2020 and we're capable of some amazing technical feats, but for some reasons the fact that we can have bidirectional communication with something so old and so far away is astounding to me.
Over the course of my life, I feel like I've read the "Voyager is going to go out of communication range/Voyager has gone out of communication range/Wait, no, they figured something out" series of stories several times.
After reading the article, I would chosen the headline "Earth is back online after eight months of radio slience". The earth station was down, not Voyager ;-)
I seem to recall from the documentary "The Farthest" that Voyager actually transmits data almost continuously, but that most of it is lost forever because the capable ground stations are only ever tuned to it for brief, scheduled windows.
It's only fitting to put a link to the Deep Space Network (DSN), displaying what all the dishes are doing right now (spacecrafts, data rates...): https://eyes.nasa.gov/dsn/dsn.html
If you've ever replaced a Ku or Ka band feed horn on a 1.2 to 1.8 meter size VSAT dish, looking at a three ton feed horn is an interesting thing to wrap your mind around.
The Mars rovers, including Perserverance, usually communicate directly over a high-speed link with one of several relay satellites orbiting Mars. The smaller antennas of the DSN can communicate with the relay satellites as well.
Furthermore, the locations of the stations aren't determined by the hemispheres. Everything DSN is used for is far enough away from Earth that it doesn't matter if the antenna is in the northern or southern hemisphere. The reason for the spread-out stations is the rotation of the Earth, which for half of the day puts the Earth in between the station and the satellite.
While the rotation of the earth is one of the primary reasons for the spacing, the hemisphere does matter for Voyager. From the article: "As Voyager 2 is heading southwards compared to Earth's orbital plane, only a dish south of the equator can send the probe a sufficiently powerful signal."
Not necessarily, Voyager 2 is pretty far angled below the ecliptic plane by 48 degrees [1]. If you were to point the Goldstone dish (35 degree N latitude) directly at the horizon you can reach as far as ~78 degrees below the ecliptic plane if you are pointing in the direction of the tilt of the earth (I don't actually know where Voyager is relative to the tilt of the Earth). If it were in the opposite direction, pointing the antenna at the horizon means you could only point at something ~32 degrees below the ecliptic. And Madrid has a slightly higher latitude at 40 deg N.
Makes me wonder about the effort put into the design of it's longevity. It must be an awesome feeling if you worked on it and so many years later there's still tangible value being extracted from it
Voyager 2 emerged from behind Saturn (as seen from the Earth) in August 1981. The scan platform had been moving feverishly—pointing here and there among the rings, moons, and the planet itself during the all-too-brief moments of close approach. Suddenly, the platform jammed. A stuck scan platform is a maddening predicament: knowing that the spacecraft is flying past wonders that have never been witnessed, that we will not see again for years or decades, and the incurious spacecraft staring fixedly off into space, ignoring everything.
The scan platform is driven by actuators containing gear trains. So first the JPL engineers ran an identical copy of a flight actuator in a simulated mission. This actuator failed after 348 turns; the actuator on the spacecraft had failed after 352 turns. The problem turned out to be a lubrication failure. Good to know, but what to do about it? Plainly, it would be impossible to overtake Voyager with an oilcan.
The engineers wondered whether they could restart the failed actuator by alternate heating and cooling; maybe the resulting thermal stresses would induce the components of the actuator to expand and contract at different rates and unjam the system. They tested this notion with specially manufactured actuators in the laboratory, and then jubilantly found that in this way they could start the scan platform up again in space. Project personnel also devised ways to diagnose any additional trend toward actuator failure early enough to work around the problem. Thereafter, Voyager 2’s scan platform worked perfectly. All the pictures taken in the Uranus and Neptune systems owe their existence to this work. The engineers had saved the day again.
Our hacks are nothing compared to the hacks of these old school nasa programmers :)