Old software keeping space missions alive
bbc.com
bbc.com
anyways, for those who don't have the patience, the title is misleading. it's just some old software from the 90s. It's only ancient if you're one of those people who completely rewrites their entire code base from the ground up every two years because to pad out your resume with whatever bullshit new "framework" is in vogue. Contrary to popular belief you actually can just keep using the same software indefinitely, it doesn't degrade with age, and for the most part the hardware lasts pretty long too as long as you take care of it (with a few exceptions like optical drives and SSDs).
It's altogether amazing.
You're probably correct, but it's more about if they would want to pick up a language that has no future, except maintenance of already existing systems. (see: Perl).
But there's excellent money in being a COBOL programmer. Some might be interested in that.
As someone who started programming in 1980, I feel your pain. My oldest spreadsheet goes back to 1995.
SSDs are random access, just not volatile like DRAM.
A tech-illiterate author/editor is the much more plausible explanation.
All of a sudden I had an urge to get MS-DOS to run with a SSD as memory. Unfortunately I know DOS can’t address 1TB of memory, but the mental image of it is hilarious.
[1] https://history.nasa.gov/afj/compessay.html
[2] https://www.tomshardware.com/news/micron-finally-rolls-3d-xp...
In the thirty years I spent developing software I spent hardly any time on anything that was accessible through the network and I'm confident that I'm not the only one. The embedded control software that I wrote for 6502s would still work today and would be completely invulnerable to attacks other than from someone standing right in front of the machine pushing buttons.
Of course now that everything has to be networked so that your fridge can advertise special offers to you the situation is changing for the worse.
What nonsense. the 90s is recent, not ancient.
“The Voyager space missions were maintained by technology that would today be artefacts in a museum”
The technology either is or isn’t in a museum right now. Why say “would today be”. If it is you can say “technology that by now you can see in a museum” and if it isn’t you could say “expect to be in a museum”.
Given the remarkable longevity of the Voyagers, what I'm surprised about is that there hasn't been much discussion about their componentry and why they've been so reliable. For example I've seen nothing written about the engineering involved in Voyagers' TWTs and why they have been so reliable.
For instance, what is the cathode material, barium, strontium, thorium oxide, etc. used in these TWTs? Was its selection criteria based on emitters with the lowest work function/highest emission at the lowest temperature with preservation of the heater life foremost in mind, and or was it based on oxides with highest ruggedness—least affected by cathode poisoning, etc. Discussions about Richardson's laws and cathode emitters is something I almost never come across these days let alone how they've played a role in the engineering of Voyagers' longevity.
Whilst component manufacturers consider these matters, terrestrial users generally don't, we just reach for replacement parts when components fail. Perhaps I'm just not reading the right material but given the remarkable performance of these spacecraft, I'm surprised we're not focusing on the science and engineering that's made that all possible.
No doubt those who're involved in space engineering are focused on these issues but it seems to me not much information has filtered down to even people like me who have some limited knowledge of the technology let alone the general science-reading public.
Using the Voyagers' history and notoriety would be an excellent way to interest students in the physics of TWTs not to mention the material science and the engineering used in their design and manufacture.
When one considers it, there's a lot of fascinating science and engineering involved in making this 'relic' from the vacuum tube era function and keeping it so.
I think part of this might be because it is still considered proprietary information. Kind of crazy, but there is really only one company in the US that makes space qualified TWTs which is Stellant systems (formerly L3, formerly Hughes microwave) who made the Voyager TWTs as well.
You're likely right about the proprietary nature of such manufacturing but perhaps I'm reading too much into this. As I mentioned in an earlier post the emission in the CRT of my 43-year-old Sharp TV is still OK—at least as far as the quality of the image is concerned.
The technology used in the Wehnelt cylinder in my TV's CRT is of a similar vintage to Voyager (I'm pretty sure the TV was manufactured around 1979), and given the millions of CRTs made to similar a quality around that time it's likely that manufacturering techniques and reliability figures were widely known throughout the industry by then.
Anecdotally, I've noticed that CRTs made from the early '70s onwards had much better longevities than their earlier '50s counterparts, whether this was because the formulation of cathode emitters had changed or manufacturing techniques had improved or both is an open question.
Of course, such comparisons are tenuous but that's all I've got to go on, for starters, the Wehnelt in the Voyager's TWT would have been deigned to carry more current. Perhaps NASA has some spare TWTs that one day someone will reverse engineer and we'll know for sure.
Nevertheless, it seems to me that knowledge about component reliability is critical to NASA, so it's likely the answer already exists somewhere in the depths of NASA's archives.
Another question I'd like answered, do the Voyagers cycle down or turn off the heater during TX downtime? Turning it off risks metal/cycling fatigue, leaving it on risks reducing the cathode life—or even poisoning it from stray ions.
A final point, presumably the TWT's output has dropped over the decades, how is this monitored and do we know the percentage drop in power output (from the TWT not the Pu power source)?
The fact the TWT is still working seems quite remarkable—but then perhaps I shouldn't be overly surprised, one of my TV sets, a 23" Sharp, is 43 years old and the CRT still works well (and it's switched on for several hours every day).
I suspect that now the heaters are turned off during Tx downtime, but I think this is probably because they Pu power is much lower and so thy want to conserve as much power as possible. Even if they did have more power, Voyager only makes contact once per day so I think the increased thermal cycling is not much compared to reduction in cathode life so they probably go this route anyway. I do know that other missions I have worked on that have much more frequent contacts, we do keep the Tx heaters on so there is probably some number of cycles where one becomes more dominant.
> A final point, presumably the TWT's output has dropped over the decades, how is this monitored and do we know the percentage drop in power output (from the TWT not the Pu power source)?
This is telemetry from the TWTAs on the helix current and the anode voltage. Along with the DC power draw of the TWTAs I think you can interpret some of what the power output is and how it changed over life. Some of this might be curve fitting to ground-based life tests so there could be some estimation. The ground is also certainly measuring the received power so they can estimate power output from the spacecraft from that as well.
> The fact the TWT is still working seems quite remarkable
You're not the only one. From this article [0] a JPL engineer says "Nobody can explain why the Voyager TWT is still working".
[0] https://spinoff.nasa.gov/Traveling-Wave-Tubes-Travel-Far
I wonder if you may know any answers to questions I put to AllanYx ?
(The HV supply on a vidicons is usually about 700V—that's high enough to be quite stressful on P/S components.)
https://buy.hpe.com/us/en/compute/apollo-systems/apollo-80-s...
502 Bad Gateway
"we have a closet full of sparc 10s, we figure that'll be enough to last as long as the satellite"
Zoom call with 100 Airbus engineers ...
The original software for part of the onboard navigation system was running on a Windows 98 PC that no-one could find the password to and ended up using bolt cutters to extract the hard drives.
Talk about a deep space horror story!
As for the password, this is the old days. Could probably google how to crack the password for it. Or just try the classic 123456, querty, password, or letmein.
I've had PC cases that had eyelets for a lock. You'd have to get through that before "unscrew(ing) the drives".
So determining how much fuel you have left is done by a combination of integrating how much time you had thrusters firing, coupled with what pressure the tanks/lines were at while the thrusters were firing. Errors in these measurements accumulate over time which is why there is a lot of effort in to determining how much fuel is left in a spacecraft. Especially critical for things like big comm birds in GEO where fuel can be limiting in operation and the more fuel you have the longer you can keep station and get revenue from the satellite. But you need to still be conservative enough to have enough fuel to get out of the GEO belt for decommissioning your satellite.
[0] https://en.wikipedia.org/wiki/Propellant_management_device [1] https://www.northropgrumman.com/space/pmd-tanks/
> I checked with Nasa, which has assured me that the spacecraft are still being controlled from the same beige cubicle in an annex of its Jet Propulsion Laboratory (JPL) that I visited in 2017, marked with a homemade cardboard sign reading: "Mission critical hardware – PLEASE DO NOT TOUCH".
I throw around the term "mission critical" maybe too easily. Because that beige cubicle with the homemade cardboard sign sounds humbling.
https://arstechnica.com/space/2023/08/nasas-buildings-are-ev...
Over the last few decades, embedded programming hasn’t changed much, for example. The rate of change is much higher with the ultra-abstracted languages.