Space Shuttle Displays Go Glass

cloudscout writes: "NASA has finally decided to bring the space shuttle up to date with a 'glass cockpit.' Until now, the space shuttle cockpit has used a system of gauges and dials designed in the early 70's. They now have full-color computer displays and controls. Pictures and details are available in this article at WESH Channel 2000. So how long until someone ports MAME to this thing?" Can anyone shed light on what sort of operating system will drive all those screens?

Comments

Microsoft Space Shuttle (TM)

[cam_macleod]

Glass screens, full colour, brand new... it's obviously Windows CE. Or Pocket Windows. Or whatever it's called this week.

NASA Administrator: "Sure, we want a calendar and a phone list in Atlantis -- but what about videos and MP3s??"

NASA Worker: "Uhh, I'll get right on that."

NASA Administrator: "Can you put in that paperclip thing too?"
- Cam MacLeod

Why retrofit these things?

[Grant Elliott]

First of all, the shuttles are supposed to be replaced within a few years (hopefully). Secondly, I can think of a lot of other things that should be updated first. Anyone know how the computer system onboard works?

There are five computers- with tape drives! The tapes aren't big enough to hold everything, so there are seperate tapes for take-off, landing, orbit, etc. The tapes need to be changed by hand on the first four machines. The fifth machine is permanently running the emergency landing routine. If one of the first four computers disagrees with the others, it is shut down. If the shuttle is ever down to two computers, the fifth machine kicks in and takes the next available landing window- with or without anyone onboard. It's never happened.

I always assumed the reason that the system never got updated was because they were planning on replacing the shuttles soon. Makes you wonder how confident NASA is about the X-33.

(This information is a few years old. Anyone know if NASA has upgraded the computers yet?)

Re:Why retrofit these things?

[Detritus]

The main computers in the Shuttle are IBM AP-101S computers. The AP-101S is a member of the IBM 360/370 family of computers.

The problem with hard drives is their fragility. They are too sensitive to vibration and hostile environmental conditions. Tape drives have been successfully flying on spacecraft for decades.

The Space Station was using radiation hardened 80386 chips the last time I checked.

Re: Why retrofit these things?

[mperrin]

There's a very good reason for not upgrading the shuttle's computers: They don't need it.

Think about it. How many other computer systems can you think of that have been running for the last twenty years? How many other systems have had the tens of thousands of hours of testing and, even more importantly, have worked flawlessly every time? The shuttle computers work. They have never failed in flight, period. Some new system? Hah. We all know how solid most applications are today. The above jokes about running CE on this shuttle show that for sure. ;-) The shuttle today does fundamentally the same thing it did twenty years ago; the calculations needed for launch and landing haven't changed. So why replace the most tested piece of code in the world with something new? Would you like to ride in the first flight with brand new software? Thought not.

Next question: So then why upgrade the displays? Partly it's economic - those bulky old dials weigh a lot, and it's still ten kilobucks a pound to LEO. Beyond that, the interface can be made far better and more adaptable than anything you can do with gauges and switches in hardware. Anything that can be done to make the pilot's life easier is a net win. They way they did it, they basically put in a new system which takes the data and runs the displays, leaving the main computers pretty much untouched, running the same ol' rock-solid code.

Another point about the backup system. As Detritus posted elsewhere, the four main machines all run a program called PASS, the Primary Avionic Software System , while the fifth computer runs BFS, the Backup Flight System. These two programs were written by completely independent groups of programmers. To this day, no one who has worked on one of them is allowed to ever see the code for the other. They're completely indepentent. The idea behind this is called "diverse design". The more dissimilar two systems are, the more improbably it becomes that both will fail at the same time. They originally wanted to have totally different hardware for the backup too, but that was nixed to save on costs. Lastly, the backup system most certainly doesn't kick in automatically, under any circumstances. It's the mission commander's call, whether to hit the big red button on the control stick or not. (And yes, it actually is a big red button.) The designers judged that it was better to keep a human in charge than blindly trust the software.

Re:Why retrofit these things?

[kzinti]

The tapes aren't big enough to hold everything, so there are seperate tapes for take-off, landing, orbit, etc. The tapes need to be changed by hand on the first four machines.

This isn't correct. There are two tape drives called Mass Memory Units (MMUs); each has an identical copy of the flight software, both PASS and BFS. The drives are physically separate units from the GPCs; for the sake of redundancy, they communicate across separate data buses. All five GPCs share the same two MMUs.

The tapes in the MMUs are large enough to hold all the flight software for the different phases of the mission. These separate programs are called "Ops modes". There is an ops mode for each mission phase: OPS 1 for Ascent, OPS 2 for Orbit, OPS 3 for Entry/Landing. There are some other modes, but these are the significant ones.

The tapes do not have to be changed during the mission, but an crew member must manually enter the command for the ops mode transitions. Within an ops mode, the flight software can make its own transitions between program phases -- these are called "major mode transitions" and don't require an access to the MMU.

I'm not a FSW expert, but I've spent the last two+ years writing GPC emulators, so I've become familiar with some of these concepts.

--Jim

More cost cutting

[djrogers]

NASA refused to comment on the OS question, however one source has told me that they got a $7,600 savings thanks to a $400 per unit rebate from MSN.....

Hmmm...

[Ravagin]

I think it's unlikely that Windows would be used. Stability issues aside, for a spaceship, you want the maximum ability for customization. I'm no Linux expert, but it sounds like it would be a good OS to use. And hey, we had that story earlier about building your own distro. That would be neat: NASA writing its own Linux distribution for the space shuttle
I'm just speculating, mind you. They could use Windows or DOS or something like that...and get all sorts of fun errors.

Life Support has caused an illegal operation and will be shut down.

c:\>Close bay doors
Bad command or file name.
c:\>Close "bay doors"
Too many parameters.
c:\>Close (bay doors)
Error reading bay doors.
Abort, Retry, Ignore?

[astronaut clicks on "Extend Landing Gear"]
Not enough memory to complete this operation. Close some programs and try again.

Oh dear....

ShuttleOS: 1 bug in 420,000 lines

[MikeApp]

Read this article in Fast Company:

They Write the Right Stuff

There have been 17 bugs total in the last 11 OS revisions of the Shuttle code, approximately 420,000 lines delivered each time.

Slightly out of date info

[luge]

This page has all kinds of crazy info on the original stuff that the Shuttle ran on. It gives a good idea of what it takes to run a shuttle- something like 6 processing units, each with about 400 KB of memory. Lots of stuff in there- details on the custom OS and language which they use, and on the extreme levels of redundancy (software written in two separate locations, 4 copies running in parallel, and an emergency landing program constantly loaded on a separate processor just in case.) Cool stuff...
~luge

What OS?

[darkbabbit]

I don't work on the shuttle, I work in the Avionic biz, which shares many similarities to the shuttle project.

The avionics biz is very conservative when it comes to items that relate to safety. The primary and secondary displays have to be so safe, bug free, and have such a small memory space that they don't use an operating system such as windows, *nix, or DOS. It is strictly bare metal programming. In the boxes that I work on, having 500k of ram to work with is a luxury item.

The graphics are usually handled by seperate chip with a dedicated graphics engine embedded into it. The main processor and graphics chip usually communicate via shared memory locations and the commands don't get any more complicated than "draw blue circle at location x,y with radius r" and many of the items come predrawn.

Shuttle GPC Operating Systems

[Detritus]

The GPCs (General Purpose Computer) in the Shuttle use two software packages. Four of the computers run PASS (Primary Avionic Software System), which was originally written by the IBM Federal Systems Division. The fifth computer runs BFS (Backup Flight System), which was originally written by North American-Rockwell. The "operating system" is unique to the Shuttle, it isn't a port of a commercial product. PASS is the primary system, BFS is there as a backup in case of a common mode software failure during ascent or entry. The Shuttle is a fly-by-wire spacecraft. All of the control surfaces, and many other critical functions, are controlled by the computers. Without an operational computer, you crash and burn. Shuttle software is written in a language called HAL/S (High-Order Aerospace Language Shuttle), which was developed by Intermetrics. The Shuttle's operating system is a hard real-time operating system based on cyclic scheduling. A task is guaranteed to get N cycles of CPU time every X milliseconds. The tasks are managed by three executives, the HFE (High Frequency Executive), MFE (Medium Frequency Executive) and LFE (Low Frequency Executive). A task that issues commands to control surfaces is going to run at a high frequency. A task that checks tire pressure (really!) can run at a low frequency.

the weight -- and more links/pics

[turg]

This CNN story is more informative and has better pictures.

The part I found amazing was that, in this conversion, the shuttle cockpit lost 25 pounds of weight. Now, CRT's aren't the lightest thing in the world, so those old dials and guages must have been pretty heavy

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not a huge suprise

[jetpack]

This isn't exactly a huge suprise to me. I had a TA in university that had previously worked on the shuttle code, and showed us the design documents and the coding procedures for some of the shuttle control code. The attention to detail was almost unreal. Even the requirements doc was triple-intense, not to mention the coding procedures themselves. The shuttle folks are coding-for-keeps, and well they should; peoples lives are *directly* on the line.

Too bad the industry-at-large refuses to be as thorough as NASA.

Computers in Spaceflight: The NASA Experience

[Detritus]

This is an interesting book on the history of computers in space, it is available on the web here. It has a chapter on the Shuttle's computer systems.

Also see CACM Volume 27, Issue 9 (September 1984) for an interesting article on Shuttle software.

Houston, we got a problem

[ContinuousPark]

I'm not sure if this is what you're looking for but it's pretty similar. It's from Wired News; they were watching NTV too and listened to this conversation where one of the astronauts had a problem with, guess what?, Microsoft Outlook. =) and called Houston for help. I suppose it was running on one of the Thinkpads that they now carry with them on the shuttle.

Re:Good luck.

[Detritus]

Doing something new in metric units is easy. Switching from English/Imperial to metric is a bitch when you have invested huge amounts of money and training in the old units.

Spacecraft navigation is the descendant of aircraft navigation which descended from the navigation of wooden ships. That is why they still use knots, feet and nautical miles.

I've wondered how we could switch to metric units for the operation and navigation of aircraft without killing thousands of people in the process. Everyone is used to "500 knots at 35,000 feet", and the air traffic control system is built around those units. How do we seamlessly change that to metric units? Plus the pilots have the old units deeply embedded in their brains. They know that the stall speed of their plane is 100 knots, the fuel consumption of the engine is 10 gallons/hour and many other important facts in the old units.

I'd rather not have glass...

[DeepDarkSky]

glass CRTs just seems a little too vulnerable to failures to me. I mean, for god's sake, it's glass! We are talking about space vehicles which may be subject to several G's of acceleration. Granted, that may not cause any problems, but if one of the CRT cracks or breaks, it will be useless. In many ways, I think that analog gauges would be more reliable. You certainly should not put several gauges together such that there's a vulnerable single point of failure. I suppose they could make it with something like bullet proof or shatter resistant glass (I hope) to remedy this proble.

Then there's the electrical system that's needed to drive such as system. What if the electrical system for the gauges were to lose power? No gauges? There should at least be backup analog gauges for some vital system gauges.

What they should also try to develop that would be better than CRTs though not as good as analogs would be some kind of flexible durable flat panel display. Something like the surface of those plastic mouse pads. You could bend it, press on it, and it would not cause significant damage. Even better still, make it so that the display is not a general purpose display, but pre-configured display that changes depending on electrical current/voltage like the analog gauges. But it would have advantage over the analog gauges because it would not have any moving parts. To get an idea of what I'm talking about, imagine those Duracell battery testers used as gauges. I mean, wouldn't that fairly resistant to all kinds of adverse conditions and abuse? And if you make them like "skins" that you could just snap in place, then you could easily carry redundant gauges because they would be very light!

Come on, they could do better than that! Or am I just completely wrong on this?!

Re:The shuttle can't land by itself

[CharBoy]

This is actually true, the Shuttle cannot deploy its landing gear in the computer. The previous users post shouldn't have been moderated down, he's absolutely correct and it is on-topic.

The astronauts objected to the computer being able to deploy the gear automatically, and this was given to them by the software people as a meaningless victory in their fight against the full automation of the shuttle.

The concern the astronauts claimed was that if a computer glitch caused the gear to deploy while in orbit, the result would be a loss-of-vehicle scenario.

The software is capable of handling every aspect of a shuttle landing except for the landing gear itself.

An interesting side note, if the gear aren't deploying within a half a second or so of the deploy switch being pressed, there are pyrotechnic charges that deploy the gear by force. As far as I know, they haven't been needed yet, but I imagine it'd be quite a sensation...

Re: GPS for aviation

[Ledge Kindred]

If you have a military GPS receiver, you can decode the encrypted military GPS signals that are on a different frequency than the civilian signals which will allow you to find your GPS coordinates down to a few inches.

But there are a lot of other reasons why GPS isn't very good for aviation use:

GPS does not handle altitude very accurately.

GPS does not handle very high speeds all that well.

I imagine the GPS system would break down entirely when you reach a good percentage of the altitude of the GPS satellites themselves. Not so good for the shuttle. (Seeing as this is what the article is about...)

Here's a great URL for lots of info on how GPS works: http://www.trimble.com/gps/index.htm (It uses Shockwave, but you can still view it without.) Here's another with lots of information about GPS units: http://joe.mehaffey.com/

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