Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Apollo On Board Computer Emulator

michael posted about 10 years ago | from the powerful-geekiness dept.

Programming 166

frankk74 writes "For those of you interested in Historical Computing and the Apollo manned spaceflights Ron Burkey has created a open source emulation of the Apollo Guidance Computer called vAGC. I use it as my desktop clock of choice. Note it only keeps mission time so after 24 hours you have reset the time :-). P.S. Another cool Apollo toy free and payware can be found here."

cancel ×

166 comments

Sorry! There are no comments related to the filter you selected.

Amazing (0, Offtopic)

Nermal6693 (622898) | about 10 years ago | (#10095126)

I'm amazed with some of the stuff people come up with. Not very practical of course, but I spend half my time doing stupid stuff - I spent most of today playing Super Mario 64!

Slashdotted (5, Funny)

dreamer8815 (757752) | about 10 years ago | (#10095132)

In three two one... Huston, we have a problem.

Re:Slashdotted (4, Insightful)

Metteyya (790458) | about 10 years ago | (#10095252)

I have a lot of respect for all the admins and webmasters for not banning their sites/servers from people-coming-thx-to-slashdot.

The coolest project I've ever seen (3, Insightful)

incog8723 (579923) | about 10 years ago | (#10095139)

Forget Linux. Forget overclocking/unconventional CPU cooling. This is cool shit.

Re:The coolest project I've ever seen (0)

Anonymous Coward | about 10 years ago | (#10095413)

And for the second link:
Forget Linux, forget open-source software, download the shareware (yuck...) and order the full version.
This sux.

Warning (4, Interesting)

poofyhairguy82 (635386) | about 10 years ago | (#10095160)

From site: For Win32 users, it's much more work to get your computer set up to build Virtual AGC than it is in Linux, and the steps needed will be less familiar.

That made me feel good seeing as how this is the first week I've tried linux.

Re:Warning (1, Funny)

ricotest (807136) | about 10 years ago | (#10095301)

I hope that thought consoles you when you're struggling with the ATI graphics card drivers or recompiling your kernel :)

Re:Warning (0, Offtopic)

paranerd (672669) | about 10 years ago | (#10095444)

Ever try recompiling your kernel?

Re:Warning (-1, Offtopic)

Anonymous Coward | about 10 years ago | (#10096151)

I'll recompile YOUR kernel, and it should be quite painful.

STFU.

Re:Warning (1)

paranerd (672669) | about 10 years ago | (#10095539)

If the grandparent thread to this reply isn't flamebait, then neither was the parent. (Yet, I'll accept my previous response as offtopic!)

Re:Warning (-1, Offtopic)

Anonymous Coward | about 10 years ago | (#10095591)

If the grandparent thread to this reply isn't flamebait, then neither was the parent.

Your family business seems to be complicated. Do you mind if we don't participate?

Re:Warning (0, Offtopic)

paranerd (672669) | about 10 years ago | (#10095973)

Well, I am from West Virginia.

Re:Warning (0)

Anonymous Coward | about 10 years ago | (#10096221)

Never had any problem compiling a kernel.

Never had any problem with the ATI drivers.

Never had any problem with this stuff. What's yours?

very simple processor (5, Interesting)

ndevice (304743) | about 10 years ago | (#10095175)

Took a quick scan at the architecture of the machine, and I'm suprised that it's so simple.

People say over and over again that simple handheld calculators are more powerful than that thing, and it seems that the oft-parroted line is more accurate than they realize.

Add to that: RTL (before TTL) and magnetic core memory bring up the nostalgic value.

Re:very simple processor (5, Interesting)

thhamm (764787) | about 10 years ago | (#10095213)

some of the "moon hoaxers" think thats why they could never get to the moon at all.
"though much faster, my pentium can barely run [insert 3d shooter here] at good FPS. how could it fly to the moon? so they never did."

logic?
clavius explanations [clavius.org] .

Re:very simple processor (4, Interesting)

TheHawke (237817) | about 10 years ago | (#10095601)

Eh, Brute force. They needed the AGC to be as simple, yet programmable with all the steps necessary to get the boys on the moon and back.
So they took the PDP8 and squeezed it down into the size of a early 80's era Kaypro portable (now that's saying something about my age) and managed to get it to draw as much power as your coffeemaker.
THEORETICALLY, they could have done it with a sextant and a good clock, BUT! Their navigation skills had to be dead-bang on every time to the fraction of a minute.
So it was easier to shoehorn this colossus into the spacecraft and let it do the driving.

Re:very simple processor (4, Insightful)

Speare (84249) | about 10 years ago | (#10095808)

But somehow a few rafts colonized the polynesian islands. Somehow a compass, a sextant and a bunch of canvas guided boats across the Atlantic for centuries.

Re:very simple processor (2, Insightful)

Daniel Dvorkin (106857) | about 10 years ago | (#10095938)

Look at just about any operation your computer performs. Not only is it all math, it's generally fairly simple math. You could do it all with a pencil and paper -- but you can't do it as fast. It's speed that's the issue. On a ship, you have time to correct your errors. When landing on the Moon ... you don't.

Re:very simple processor (4, Insightful)

Archibald Buttle (536586) | about 10 years ago | (#10095910)

The hoaxers are dicks.

It is of course completely irrelevant that their pentium is a heap of crap, as you imply. These are the kind of idiots that don't believe that you could have a 3d game on a 20 year old 8bit micro - showing them Elite blows their minds.

They think that because a computer is slow it's worthless. Well, that's what Microsoft and Intel keep telling us so it must be true. Also their 3d shooter is damn slow. That's gotta be proof.

Conversely those of us with brains, real software development knowledge, and an appreciation of physics realise that you hardly need any computing power at all for an Apollo space craft. Indeed it's arguable that the computer they did have was overkill - a computer-less solution could have been engineered.

Re:very simple processor (4, Insightful)

RedWizzard (192002) | about 10 years ago | (#10095251)

People say over and over again that simple handheld calculators are more powerful than that thing, and it seems that the oft-parroted line is more accurate than they realize.
Or perhaps they repeat it because it's accurate and they know it?

Re:very simple processor (5, Interesting)

Edward Teach (11577) | about 10 years ago | (#10095292)

In the Apollo 11 descent to the moon, you hear someone say "twelve oh one alarm." This was the alarm that told the LM crew that the computer reset because it ran our of memory.

Re:very simple processor (2, Informative)

Anonymous Coward | about 10 years ago | (#10095597)

No, it didn't 'run out' of memory, there was no OS capable of making that determination. There were simply too many real-time interrupts coming in. The time-slice approach of the Apollo system simply couldn't handle all those requests.

Re:very simple processor 1201 (3, Informative)

Tuna_Shooter (591794) | about 10 years ago | (#10095642)

Also, I beleive that they left the rendevous docking radar switch in the on position during decent (a no no) also contributed to the 1201's. Even though it was listed in the Flight manual as being in the on postion. A mistake i believe that wasnt tested in the simulators but was found by 2 engineers during a passing conversation in a hall.

Re:very simple processor (4, Funny)

oogoliegoogolie (635356) | about 10 years ago | (#10095787)

...the computer reset because it ran our of memory.

That's because when the LM was being designed some engineer decided "640 Bytes should be enough for anyone."

Re:very simple processor (2, Funny)

Kenshin (43036) | about 10 years ago | (#10096170)

Wow. The last thing you want on the descent to the moon is a BSOD...

ummm.... (-1, Troll)

Anonymous Coward | about 10 years ago | (#10095176)

um, dumb ass, if its open source, why dont you just make it keep real time? or are you just an OSS poseur who cant program?

Ahh, it's the Missing Piece! (3, Funny)

Anonymous Bullard (62082) | about 10 years ago | (#10095205)

Now the Chinese Communist Party can finally be confident that their Soviet-era space capsule can be launched at the moon, with one or two "People's Liberation" Army's faithful inside.

Like Deng Xiao Ping's 50-year plan towards (real) World Domination by using the capitalists' greed against their own long-term interests, this space-conquering plan began over 50 years ago when the "People's Liberation" Army invaded their peaceful neighbour Tibet, to be used as a back-up landing area. Well, Tibet can also be looted for their natural resources (oil, gas, uranium) and subjugation the hapless Tibetan people has been used as a great propaganda victory for Party jingoism, but clearly one of the main reasons to invade was to use the Tibetan territory as a back-up landing site.

Apollo On Board Emulator, running on Red Flag Linux and locally-built Dragon CPU... even Evil Invading Dictatorships can be pretty geeky when it suits their World Domination Plans... ;-)

Re:Ahh, it's the Missing Piece! (-1, Offtopic)

Paulrothrock (685079) | about 10 years ago | (#10095471)

I don't see how this is funny. Well, except for that last part.

China is turning from a communist dictatorship to a fascist dictatorship, and we keep giving them money to oppress their people and build nuclear weapons.

Are the rights of a chinese worker worth less than the rights of an American worker? If not, then we should not be supporting a government who denies people their fundamental rights and pollutes the environment.If so, then those rights were never cherished by us in the first place, or we have been blinded by greed.

Yes, I realize the irony of using a Chinese-made computer to deliver and anti-Chinese message.

Re:Ahh, it's the Missing Piece! (0, Offtopic)

Twirlip of the Mists (615030) | about 10 years ago | (#10095586)

Are the rights of a chinese worker worth less than the rights of an American worker?

To an American? Yes. To a Chinese person, it's the other way around.

I'm neither celebrating nor bemoaning this basic fact of human nature. But you seem to be either unaware of it or unwilling to acknowledge it.

Lots of bad things happen when people choose to ignore human nature.

12-bit Instruction set (3, Insightful)

Anne Thwacks (531696) | about 10 years ago | (#10095212)

A quick inspection of the instruction set reveals why they only made 157 of these and made 6 million PDP8s.

Re:12-bit Instruction set (4, Insightful)

Rosco P. Coltrane (209368) | about 10 years ago | (#10095228)

A quick inspection also shows that a PDP8 weighs as much as the Saturn V rocket, and weight is the last thing they needed to haul stuff on the moon...

Re:12-bit Instruction set (4, Informative)

hughk (248126) | about 10 years ago | (#10095290)

Not really, and it had an excellent reputation for real-time work. The thing is when NASA were shopping for processors a long time before the landing, the PDP-8 didn't exist in the compact form. By the time of the first landing it certainly did, but it was already too late. The PDP-8 and later the PDP-11 then just swept through the world of real-time computing.

Re:12-bit Instruction set (2, Informative)

melonman (608440) | about 10 years ago | (#10095369)

Also, it takes a long time to get electronic components approved for use in space, which is why the stuff in satellites is usually way behind what sits on your average desk. The university I attended designed and launched a series of very cheap satellites, which, apparently, ran some of the most advanced computing equipment in orbit, simply because it didn't matter too much if it blew up after 3 days.

Re:12-bit Instruction set (1)

gatkinso (15975) | about 10 years ago | (#10095398)

It also sucked more juice than the average house does today.

Re:12-bit Instruction set (0)

Anonymous Coward | about 10 years ago | (#10095697)

On closer inspection, these are loafers!

Re:12-bit Instruction set (5, Funny)

kfg (145172) | about 10 years ago | (#10095237)

A quick inspection of an Apollo capsule reveals why they didn't just use a PDP8.

Think of three fat guys trying to move one of those things in a Mini Cooper.

KFG

Re:12-bit Instruction set (5, Funny)

AndroidCat (229562) | about 10 years ago | (#10095482)

And they made Buzz Aldrin sit in the back. No wonder he gets cranky [csicop.org] if someone says that he didn't go to the Moon!

Simulation - emulation environment (5, Interesting)

Anonymous Coward | about 10 years ago | (#10095223)

What I would like to see is a complete Apollo computing system simulator, consisting of the hardware simulator, where you could realistically simulate the effects of increased core voltage, heat, power surges, fluctuations, etc. coupled with the hardware emulator capable of running native Apollo code, just like vAGC.

Do they have this at NASA? For them it must be easier and more reliable to just use an identical environment for testing purposes, but some Apollo enthusiasts would enjoy tinkering with such a combined simulation-emulation environment (SEE).

Re:Simulation - emulation environment (2, Interesting)

thhamm (764787) | about 10 years ago | (#10095266)

then integrate the whole thing into Orbiter [ucl.ac.uk] .
this would be incredible. not just simulating the whole spacecraft in such detail, but actually doing the whole flight.

i wasnt my fault. i they tell me to stir the tanks, i stir the tanks.

Re:Simulation - emulation environment (0)

Anonymous Coward | about 10 years ago | (#10095283)

Yep, that would be very exciting! I have a feeling someone is already working on making this happen, so I'm getting an astronaut suit to make the experience as realistic as possible when the time comes!

Oh man, can you believe there are no astronauts selling their suits on eBay?! What a bummer! It's easier to create the SEE + Orbiter system than get an astronaut suit, even a used one! *rolling eyes*

MOD parent UP - see next post by Orbiter (0)

Anonymous Coward | about 10 years ago | (#10095298)

MOD parent UP - see next post by Orbiter about work being done as referenced in parent post!

Re:Simulation - emulation environment (1)

Twirlip of the Mists (615030) | about 10 years ago | (#10095593)

Oh man, can you believe there are no astronauts selling their suits on eBay?!

Astronaut suit? You mean space suit? Apart from the fact that the astronauts have never owned them, I doubt you could pay the million bucks one would cost, much less the hyperinflated auction price.

Orbiter (4, Informative)

0123456 (636235) | about 10 years ago | (#10095291)

"then integrate the whole thing into Orbiter."

Already being worked on:

http://mysite.wanadoo-members.co.uk/marui/orbite r_ agc.jpg

Re:Orbiter (2, Informative)

0123456 (636235) | about 10 years ago | (#10095347)

Hmm, for some reason that link got screwed up: here's another try [wanadoo-members.co.uk] .

Re:Orbiter (1)

thhamm (764787) | about 10 years ago | (#10095358)

have you got more info than the picture yet? features? :)

Re:Orbiter (2, Informative)

0123456 (636235) | about 10 years ago | (#10095367)

Currently the programs run, but the IMU hardware simulation isn't there, so it can't control the spacecraft...

Source is here [wanadoo-members.co.uk] .

Re:Simulation - emulation environment (1)

Gordonjcp (186804) | about 10 years ago | (#10095751)

I wonder if you could model the electronics in Spice or something similar? The RTL logic was, if memory serves, made out of discrete components. You could actually build your own in hardware, although it would be very time-consuming. One for the dedicated electronics hobbyist, I think...

Re:Simulation - emulation environment (1)

dswartz (749795) | about 10 years ago | (#10096199)

I do not know about Apollo (I think that program might have had its funding cut), but I believe the ISS has (or will have) a complete simulator of the type you described, developed by the USA (not the country).

How do they get to the moon... (5, Funny)

Purifier (782794) | about 10 years ago | (#10095247)

...without having a "Start" button? ;)

Re:How do they get to the moon... (0)

Anonymous Coward | about 10 years ago | (#10095256)

If they had had a 'Start' button they would never have made it to the Moon. Or haven't you heard of the Blue Screen of Death?

Duh... (0)

Anonymous Coward | about 10 years ago | (#10095267)

> They put Internet Explorer in the Startup folder.

Where do you want to go today?

Re:Duh... (2, Funny)

AndroidCat (229562) | about 10 years ago | (#10095446)

If it gets infected with Gator/Claria, it'll probably take them somewhere that sells printer ink and toner.

Re:How do they get to the moon... (2, Funny)

bytesmythe (58644) | about 10 years ago | (#10095280)

They just used LaunchPad [digitalriver.com] ... ;)

Re:How do they get to the moon... (0)

Anonymous Coward | about 10 years ago | (#10095707)

Haha. I work there. I wouldn't trust a spaceship launch to it. I wouldn't trust an Internet Explorer launch to it!

/really works for Digital River (online store) not Computer Associates (Software vendor) and therefore posting anonymously.

Re:How do they get to the moon... (1)

cammoblammo (774120) | about 10 years ago | (#10095287)

Where do you want to go today?

Slingshot (5, Funny)

Hypharse (633766) | about 10 years ago | (#10095260)

I tried to use this to run games. It didn't work at first, there just wasn't enough power. Then I used the gravitational pull of my neighbor's house as a slingshot and was running Doom 3 in no time.

I wonder...... (2, Funny)

bhaynes (777260) | about 10 years ago | (#10095263)

......how long it will take someone to try and load it up with pr0n. "Huston, we have a REALLY BIG problem......"

Re:I wonder...... (2, Funny)

Anonymous Coward | about 10 years ago | (#10095309)

Bah. Apollo computers only has a numneric display. The hottest pr0n that it can display is number "69" in all fields.

Re:I wonder...... (0)

Anonymous Coward | about 10 years ago | (#10096262)

What is it with Slashdot readers and the inability to spell "Houston?"

I read that the first time and thought "what the hell is Huston? Ohhhh, Hou ston!"

Game anyone? (4, Funny)

NewtonsLaw (409638) | about 10 years ago | (#10095269)

Does someone have a copy of that old favourite: "Lunar Lander" which runs on this emulator? :-)

Hell, even my Texas Instruments card-programmable calculator played that game!

Re:Game anyone? (1)

Fallen Andy (795676) | about 10 years ago | (#10095379)

spits venom jealously. I had to key in all (let me see 96 steps?) out of 100 possible on my first programmable (a TI SR56) (c.a. 1976)
Oh and of course it forgot everything when you switched it off.

Don't touch... (-1, Offtopic)

Anonymous Coward | about 10 years ago | (#10095375)

... my yaYUL!!!

firSt (-1, Offtopic)

Anonymous Coward | about 10 years ago | (#10095390)

Officers. Oth3rs

ouch my eyes (1)

mattr (78516) | about 10 years ago | (#10095411)

I feel sorry for the guys who have been spending a lot of time on tis yaAGC.. cool but is there a good reason for a light green on light grey simulated lcd display? I can barely make out what the figures are supposed to me and it would seem to cause fatigue. On the heels of the Siemens story.

Space Shuttle computers (4, Interesting)

Veteran (203989) | about 10 years ago | (#10095421)

An engineer I work with at JSC has an actual - legally obtained Space Shuttle flight computer. The government declared it surplus, and he bought it from the surplus section, so he has the paperwork documenting that he is the legal owner. His box is an actual flight unit, which was in space, not a ground test unit or engineering sample. He has the paperwork documenting its complete history.

Every once in a while you can find some incredible things in government surplus.

Re:Space Shuttle computers (1)

TehHustler (709893) | about 10 years ago | (#10095483)

Can he do something with it at home to get it running? Not sure what he'd do with it at home, like, but it'd be cool nontheless.

Re:Space Shuttle computers (2, Interesting)

Veteran (203989) | about 10 years ago | (#10095541)

I believe he has powered it up, and it does work.

Re:Space Shuttle computers (0)

Anonymous Coward | about 10 years ago | (#10095994)

Unfortunately, all the tiles fell off his roof ...

Should it ever need a new home (1)

wowbagger (69688) | about 10 years ago | (#10095997)

Should your friend ever decide that he needs to give that computer a new home, send it here [cosmo.org] .

Re:Space Shuttle computers (0)

Anonymous Coward | about 10 years ago | (#10095621)

I bought a 1GHz sampling scope plug-in from 1964 with a NASA-LANGLEY property tag on it, via eBay. Who knows what waveforms they were looking at back then with it??

Linux (2, Funny)

schweini (607711) | about 10 years ago | (#10095430)

Darn. another platform to port linux to! Just when we thought we had most architectures covered :-)

But seriously: would it, theoretically (!), be possible to write a x86 emulator on something like that?

Re:Linux (3, Funny)

AndroidCat (229562) | about 10 years ago | (#10095456)

If you can write a Turing Machine on it, you're there. Just give it a long enough R/W tape, and let'er rip! (I will warn you that your FPS frame rate will suck.)

Not comparable in any way to calculators (4, Interesting)

panurge (573432) | about 10 years ago | (#10095452)

This machine is optimised for the acquisition of fairly real-time data; read the architectural description. Multiple channel counters are implemented in hardware, partly because in the days of discrete logic this was relatively easy to do (and, of course, the tube calculators with which people had gained experience used lots of counters, because it is relatively easy to make a counter tube, while binary tube logic is very hardware inefficient.)

Calculators have absolutely minimal I/O and need hardly any interrupt handling capability, and general purpose CPUs like the PDP-8 require a great deal of external hardware to give efficient programmed I/O. It was only really with integrated electronics that general purpose CPUs became appropriate for real time instrumentation and control.
It's also important that in a space environment, every added gate is a hazard because it can get flipped by radiation. The ideal is to have the minimum gate count, minimum memory cell count, and the shortest possible path between phyical I/O and computing. The computers used in the Apollo meet this requirement.

Sorry to restate what may be obvious to some people, but a lot of people here will never have had to implement a rad-hard design, and will not understand why simplicity and directness are such virtues in design for space use.

Re:Not comparable in any way to calculators (0)

Anonymous Coward | about 10 years ago | (#10095568)

I beg to differ ... ... why then, to all these geeks have SO much aluminum foil on hand, if not to stop radiation?

Next step: hardware (2, Funny)

H_Fisher (808597) | about 10 years ago | (#10095470)

How long before somebody cobbles together a "system" this will run on - a re-creation of the hardware using today's components, or at least a neat-looking case for this emulator?

I'm sure somebody out there with more time than I have is working on it ... :)

Re:Next step: hardware (1, Funny)

Anonymous Coward | about 10 years ago | (#10095545)

A neat looking case? Uh, I think NASA did. Back in the 60s. I don't know. Something to do with the moon.

Disaster waiting to happen (4, Insightful)

Veteran (203989) | about 10 years ago | (#10095508)

I had occasion to look at the plans for the oxygen tank that blew up on Apollo 13. There is no great mystery why it blew up, the mystery is why they didn't all blow up.

Trying to figure out how much is left in a liquid oxygen tank in outer space is not an easy task. If you wanted to know that answer here on earth you would weigh the tank - which obviously won't work in free fall.

The idea they came up with was to have a sensor in the tank that could measure the level by resistive means. In order to have a 'level' to measure they had to create an artificial gravity inside the tank by swirling the contents with an internal electric motor and a blade. In the movie "Apollo 13" one of the astronauts talks about "stirring the O2 tank", that is what he is talking about.

Consider what this all means: you have a tank full of liquid Oxygen, you have several pounds of highly combustible aluminum and graphite parts which are soaked in liquid Oxygen, and you have a DC motor with brushes sparking up a storm inside the tank. Another name for such a combination is a "bomb".

NASA's - management driven - engineering has long been full of "Whir click, whir click - OK, Russian Roulette is flight certified as safe" thinking. Nobody does a "how could this all go wrong" analysis.

Re:Disaster waiting to happen (1, Insightful)

Anonymous Coward | about 10 years ago | (#10095618)

That is really amazing. I'll look it up, of course, but it sounds about right. I would have used some ultrasonic transducers or beta probes or something to sense the level... Who knows what state those where in in the 60s but I know they used the beta probe approach to sense fuel level in airplanes back then.

Re:Disaster waiting to happen (2, Interesting)

peawee03 (714493) | about 10 years ago | (#10095639)

Not posting this as troll, flamebait, or anything other than a matter of engineering: could you do better?

Re:Disaster waiting to happen (2, Insightful)

Veteran (203989) | about 10 years ago | (#10095670)

i would have suggested an external motor with magnetic coupling to an internal stirring blade - similar to what is done in chemistry labs.

Measuring how long the stirrer takes to come up to speed tells you the mass of what you are accelerating.

Re:Disaster waiting to happen (2, Interesting)

Beryllium Sphere(tm) (193358) | about 10 years ago | (#10095951)

Maybe a capacitive measurement? Liquid oxygen must have a different dielectic constant from gaseous oxygen.

Re:Disaster waiting to happen (2, Insightful)

wideBlueSkies (618979) | about 10 years ago | (#10095780)

Just thinking about this...could we not tell the mass of the liquid in a tank by shaking it slightly? The time/energy it takes to get the tank moving, combined with the momentum after turning off the shaker could probably determine how much stuff is in there.

Or another alternative...sonar...sound reflected off the contents of the tank.

wbs.

Re:Disaster waiting to happen (1)

Veteran (203989) | about 10 years ago | (#10095838)

Good idea, the problem you need to solve with it is potential for leakage from the fittings.

I think I would use a small Gamma emitter with a radiation sensor to measure absorbtion instead of sonar, since bubbles could affect the sonar.

nope Re:Disaster waiting to happen (4, Informative)

WolfWithoutAClause (162946) | about 10 years ago | (#10095935)

In order to have a 'level' to measure they had to create an artificial gravity inside the tank by swirling the contents with an internal electric motor and a blade.

They didn't use artificial gravity to seperate the LOX; quite the opposite.

In fact, in zero gravity LOX tends to divide up into regions of gas and liquid. If the gas happens to float past the sensor, then they get an incorrect reading of the density, and hence they don't know how much is in there. This was a big problem on previous flights. Stirring the tank mixes it all up and makes it the same density; allowing a reliable reading to be taken.

you have several pounds of highly combustible aluminum and graphite parts

Aluminum, particularly bulk aluminum is *not* combustible in LOX. It's used on the Space Shuttle main tank fer heavens sake!

Graphite can't really burn either; for it to burn it needs to reach ~3000K, and the LOX is pretty keen on it not reaching that temperature.

LOX only really explodes in contact with greases- it's soluble in them, and they form a contact explosive.

and you have a DC motor with brushes sparking up a storm

Provided the brushes are carefully chosen, this need not be a problem.

That's not actually what caused the explosion anyway.

During testing a relay welded itself shut due to incorrect voltages. In flight, the wiring overheated- and the insulation burnt in the LOX. That caused the LOX tank to overpressure, and it blew away half the side of the vehicle.

Parent is informative, deserves upmod (4, Informative)

Beryllium Sphere(tm) (193358) | about 10 years ago | (#10095966)

In addition, the incorrect voltages during testing were the result of failed communication between the contractor and NASA, a spectacular example of why the paperwork is important.

Re:nope Re:Disaster waiting to happen (5, Interesting)

Veteran (203989) | about 10 years ago | (#10096168)

They didn't use artificial gravity to seperate the LOX; quite the opposite.

In fact, in zero gravity LOX tends to divide up into regions of gas and liquid. If the gas happens to float past the sensor, then they get an incorrect reading of the density, and hence they don't know how much is in there. This was a big problem on previous flights. Stirring the tank mixes it all up and makes it the same density; allowing a reliable reading to be taken.


Yes and no. In zero g the bubbles and liquid have no reason to separate. In a gravity field the bubbles float just like the do in water - so you get a liquid without voids in it - which you can measure.

Aluminum, particularly bulk aluminum is *not* combustible in LOX. It's used on the Space Shuttle main tank fer heavens sake!

Aluminum will burn in air if there is enough energy to break through the surface layer of aluminum oxide which builds up on the surface. In fact aluminum is so reactive with oxygen that this layer forms instantly when the metal is exposed to oxygen. Anything which will burn in air will really burn in LOX.

Graphite can't really burn either; for it to burn it needs to reach ~3000K, and the LOX is pretty keen on it not reaching that temperature.

There was an experiment where a scientist used LOX and charcoal to see how fast it would burn - it esentially flashed in less than a second. DO NOT ATTEMPT THIS. IT IS RIDICULOUSLY DANGEROUS. Your statement is like saying Nitro Glycerin is safe to have in your house. NOTE FOR THE YOUNG AND INEXPERIENCED: DO NOT STORE NITRO GLYCERIN IN YOUR HOUSE. IT WILL BLOW UP AND KILL YOU!!!

Provided the brushes are carefully chosen, this need not be a problem.

This is exactly the sort of thinking which resulted in the original disaster. Brushes are mechanical devices - there is inductance in a motor - when the brush connection is broken the inductance of the motor will cause a spark. We have studied the ignition properties of such sparks in LOX in my group. There is a statistical probability of a given spark igniting the brush material.

That's not actually what caused the explosion anyway.

During testing a relay welded itself shut due to incorrect voltages. In flight, the wiring overheated- and the insulation burnt in the LOX. That caused the LOX tank to overpressure, and it blew away half the side of the vehicle


That is the official theory which was reached by people who knew nothing about the spark ignition problem. The voltage in the GFE power supply used in the test was not enough to weld contacts - the LOX would have cooled the wires so that they wouldn't have reached ignition temperature. The explosion didn't happen until the tank was stirred. The thinking behind reaching that official theory was "Well none of the other tanks blew up so the design was OK so it must have been someing which was done to that particular tank that caused the problem."

Thanks for demonstrating the "Whirr click, whirr click " mind set to everyone.

Why look at the apollo flight computer (3, Informative)

stinky wizzleteats (552063) | about 10 years ago | (#10095512)

When you fly [orbitersim.com] it?

The most recent version of the apollo spacecraft add-on (NASSP 5) has a partial working AGC built into the navigation system.

Re:Why look at the apollo flight computer (2, Informative)

Queuetue (156269) | about 10 years ago | (#10095865)

Actually, it uses *this* AGC.

Car-PC (2, Funny)

LakeSolon (699033) | about 10 years ago | (#10095535)

Does anyone else have a sudden urge to run this on the touch-screen of their car-pc? I can't wait...

~Lake

Re:Car-PC (2, Funny)

Dr. GeneMachine (720233) | about 10 years ago | (#10095636)

Just be sure to have a lot of space in your trunk for all the punched tapes containing the data for your navigation system....

Anyone get a good look at the code yet? (5, Funny)

today (27810) | about 10 years ago | (#10095693)

Humorous snippet from the landing module code...

P63SPOT3 CA BIT6 # IS THE LR ANTENNA IN POSITION 1 YET
EXTEND
RAND CHAN33
EXTEND
BZF P63SPOT4 # BRANCH IF ANTENNA ALREADY IN POSITION 1

CAF CODE500 # ASTRONAUT: PLEASE CRANK THE
TC BANKCALL # SILLY THING AROUND
CADR GOPERF1
TCF GOTOP00H # TERMINATE
TCF P63SPOT3 # PROCEED SEE IF HE'S LYING

P63SPOT4 TC BANKCALL # ENTER INITIALIZE LANDING RADAR
CADR SETPOS1

TC POSTJUMP # OFF TO SEE THE WIZARD ...
CADR BURNBABY

Re:Anyone get a good look at the code yet? (2, Interesting)

Quatloo (805125) | about 10 years ago | (#10095706)

And its nice to see octal again too!

Interesting time limit (2, Funny)

Chemisor (97276) | about 10 years ago | (#10095814)

> Note it only keeps mission time so after 24 hours you have reset the time

Yeah. 24 hours ought to be enough for everybody.

Curious about the computers back on the ground (1)

Beryllium Sphere(tm) (193358) | about 10 years ago | (#10095990)

Does anyone have the specs on the mainframes NASA used for orbit calculations, mission planning and so on? I was wondering when personal computers reached the equivalent power level, and whether my Prius has more computing power on board.

Beowulf comment ... (4, Funny)

Alain Williams (2972) | about 10 years ago | (#10096064)

If we have a Beowulf cluster of these, do we have a space invasion on our hands ?

If so: who is invading who ?

Draper Labs built the AGC (4, Informative)

dswartz (749795) | about 10 years ago | (#10096141)

I would just like to point out that Draper Labs in Cambridge, MA (the company I work for) built the AGC. An exact replica of the real AGC sits in our Simulation Lab.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>