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Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

nasa.gov

41–50 of 128 posts

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#41
post #10

>This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

There are a lot of really good links, but to be honest 99% of the secret to writing bulletproof code is “write the most simple, boringest program you can”.

Which is not to say that what NASA and its contractors do isn’t cool or that they don’t spent ungodly amounts of time and money on testing and verification, but you also don’t load one line of code more than is absolutely necessary onto a machine that absolutely must work at all times.

It’s an important lesson to learn and a good skill to exercise from time to time, but honestly it’s also something that doesn’t apply to most of our work as software engineers. For most software most people are willing to knock a couple of nines off the reliability of a piece of software in exchange for higher-quality output, lower costs, and more features. If my data analysis pipeline fails one time in ten because an edge case can use all the memory in the world or some unexpected malformed input crashes the thing but yields more useful output than if I kept it simple and hand-verified every possible input, well, that can be a fine trade off. If your machine learning model for when to retract the solar panel occasionally bricks and leaves the panel out to be destroyed, that’s less acceptable.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#42
post #10

>This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

also, I would imagine that there would be a strong bias towards reuse...which leads you to long term standardization of not just language but also CPU architecture.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#43
post #10

>This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

Hello! I’m a FSW dev at NASA Langley. As others have said, the talks from the FSW workshop are a great start. If you want to see a well-used framework, check out CFS (https://cfs.gsfc.nasa.gov)

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#45
Towards the end, it says:

> “After launch, Parker Solar Probe will detect the position of the Sun, align the thermal protection shield to face it and continue its journey for the next three months, embracing the heat of the Sun and protecting itself from the cold vacuum of space.”

What a phenomenal piece of engineering! The article was not only fascinating to read as a non-astronomer/lay person, but it also makes it all look like child’s play, the way they decided what materials to use and how.

> “And to withstand that heat, Parker Solar Probe makes use of a heat shield known as the Thermal Protection System, or TPS, which is 8 feet (2.4 meters) in diameter and 4.5 inches (about 115 mm) thick.“

So is someone going to be bothering someone else about TPS Reports [1] over the expected seven year span of this probe? Sorry, I couldn’t resist making that reference! :)

[1]: https://en.m.wikipedia.org/wiki/TPS_report

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#46

http://earthsky.org/space/heat-shield-parker-solar-probe It appears the heat shield is a carbon sheet sandwich. At first I was guessing some form of tungsten-carbine, but that is the traditional material of NASA heat shields. > Why is the solar wind a breeze closer to the sun but a supersonic torrent farther away? Why is the corona itself millions of degrees hotter than the surface? I suspect the answer to all those…

"Why is the corona itself millions of degrees hotter than the surface? I suspect the answer to all those questions is simply gravity, but it will be nice to verify such things with data" Can you explain your hypothesis a bit?

Not GP, but here's an article that talks about it. Note that this is relatively recent. It's not something that was thoroughly understood in ancient times exactly.

https://www.nasa.gov/feature/goddard/sounding-rockets/strong...

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#47
post #10

>This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

also, I would imagine that there would be a strong bias towards reuse...which leads you to long term standardization of not just language but also CPU architecture.

Hello! FSW dev from NASA Langley here. We do try to do reuse as much as possible, but small satellites (CubeSats) are starting to change that. There are so many new pieces of hardware and so much experimentation going on to see what’s feasible in space. There are new RTOS frameworks being developed both by commercial and government (CFS, F-prime). If you’re interested in this in particular there is a conference called SmallSat which hosts the talks from previous years. https://smallsat.org

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#48
post #23
post #4

Dad joke: "They'll go at night" But really, it's cool that they're using carbon-carbon protection similar to that which was originally developed for the leading edges of the Space Shuttle. And I really want to know how they built foamed carbon for the interior. I'm guessing that they're using white ceramic paint on top instead of a reflective foil shield (like the Webb uses) because the foil would be shredded by the…

I'm curious about the foam, too. Normally, foam contains a lot of air. But that kind of foam will blow itself apart in a vacuum. How do they make foam where all the air pockets are replaced with vacuum? Is vacuum-filled foam a better or worse insulator than air-filled foam?

And if the foam cells have a vacuum in them (in? lack of?) how does it not implode when on earth.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#49

Earlier quoted context omitted.

The part that I find the most intriguing is "corrections can be made on the fly". I can see how you would ensure reliability through proper requirements specification, a good software development process, separate independent implementations and extensive verification. However, every time I read a popsci article about space flight software, they talk about this capability to push new code to the spacecraft while it i…

There is usually a piece of software running on the machine which basically just does this - allows you to command an image upload to the SSD, do a checksum of the file, then install it if all goes well. There is also usually a simpler version of the software on a redundant SSD or partition which the onboard computer will install if it detects that the software that is currently installed is malfunctioning. My unders…

Thanks for the reply! So what you're saying is that it's just a "normal" over-the-air software update. I.e. you add some new functionality and then do a full system test of all functions of the software before replacing the entire image?

That makes sense, but is almost a bit disappointing. After all, that is exactly how it works for the boring systems here on earth. From various wired & co articles I had the impression that there was possibly something more; a mechanism that would allow users to send elaborate "commands" to the spacecraft to perform "ad-hoc" tasks at runtime. (What I mean by "ad-hoc" tasks are tasks that are unknown at the time of validation/testing of the software.)

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#50
post #10

>This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

Hello! I’m a FSW dev at NASA Langley. As others have said, the talks from the FSW workshop are a great start. If you want to see a well-used framework, check out CFS ( https://cfs.gsfc.nasa.gov )

Off topic, but I've always been interested by the way that government agencies almost exclusively choose acronyms for their software. Meanwhile private companies (especially in the last decade or two) almost always choose unrelated, single words.

It initially seems kind of ridiculous to me that everything has an acronym, but I suppose it's no more ridiculous than choosing a name that sounds like a Pokemon. Maybe less so.

In any case, thanks for sharing that.

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