Did You Know? The Space Shuttle Runs On Only One Megabyte Of RAM!

It’s true! NASA’s space shuttle is controlled by a computer running on only one megabyte of RAM. How is this possible? Since the space shuttle and all its hardware is over 30 years old, so is its computer. The current computer is actually an upgraded version of the 500-kilobyte computer that was used until 1991, but still based on the same outdated technology from the 1980s.

NASA Space Shuttle Launch

So how does the computer process all those complex calculations with only one megabyte of RAM? Well, the shuttle, unlike the average modern computer, doesn’t need a complex graphical user interface and all the fancy programs and games we use. All it does is process the raw data it gets from all the sensors and coordinate the shuttle’s functions, in a simple UNIX-like environment. True, all those calculations are complex, but they do not require a more powerful computer than they already have.


Still, why weren’t the old computers replaced with newer ones? As the popular saying goes, don’t repair what’s not broken. If new computer systems were to be installed, they would require massive testing until they were nearly 100% fail-proof. You wouldn’t want to get a “Blue Screen Of Death” in the middle of a launch, would you? And during the past 30 years the computer system performed nearly-flawlessly. Another reason would be NASA’s budget constraints. Why spend money on something that’s working well anyways, instead of doing something useful in space?

Similarly, the Russian Soyuz capsule’s computer ran on only 6 kilobytes of RAM until it was replaced with newer systems in 2003, which most probably was the cause of its subsequent crash-landing in Kazakhstan.

If newer space launch technology is going to replace the space shuttle when it is decommissioned at the end of this year, perhaps it would include more recent computer systems, since they would have to design the whole thing from scratch anyway.

NASA Space Shuttle Before Launch

Images Credits: NASA



Paul is the the founder of CosmoBC.com. He enjoys programming and blogging on topics such as technology, astronomy or offbeat. You can find him on his website or follow him through the buttons below.

28 comments on “Did You Know? The Space Shuttle Runs On Only One Megabyte Of RAM!

  1. You would think that out of shear desire to make a system ready for errors that they would have been over doing something like this for years. Mind blowing that they haven’t!

    The whole point is… it doesn’t have or make errors…

    Duh!

  2. “Outdated technology from the 1980s”?

    Try late 1970s. The first test flight was in 1981, so the computer systems were designed and built well before that.

  3. “Outdated technology from the 1980s”?

    Try late 1970s. The first test flight was in 1981, so the computer systems were designed and built well before that.

    Yes you’re right. Though when they upgraded it in 1991 I think they used hardware slightly more recent than that.

  4. A teacher once told us the golden rule for his class was KISS (Keep It Simple, Stupid!). Sounds like KISS applies in this case. I’d heard of this before–I think the computer simply controls the thrusters on re-entry. There is probably more risk in upgrading it than not.

  5. Most “more recent computer systems” are poorly engineered over-clocked pieces of crud that would be out of place on a space shuttle or any serious hardware. An x86-powered space shuttle? I don’t think so, I wouldn’t trust it to control a car let alone a shuttle. More RAM and a more complex processor means more things that can go wrong, so yes, keep it simple.

  6. I know this article is supposed to make people gasp with surprise but it shouldn’t really.
    The computers on the shuttle are designed with a specific purpose, to guide the shuttle. The computers essentially run one application. The application will have been designed such that the amount of memory needed will be known precisely at design-time and I’m pretty sure there’s no dynamically allocated memory :-)

    This article is like saying ‘OMG your washing machine only has 64KiB RAM’; it has the exact amount of memory required to do it’s single job.

  7. I took a computer science class in assembly language in college taught by a guy who used to code for the shuttle. All the code for the shuttle is written in assembly which is the most basic practical language for writing software. The idea is to build it absolutely fail proof. It has 4 computers running the same program at the same time and if one of them has an error it is kicked off line and the other three take over. It also has a fifth backup computer running a different set of code designed to do the same thing in case all four have problems it takes over.

  8. Well don’t worry, the Shuttle has the latest computer upgrades. They went from the 80386 chip to the 80486 CPU in the 5 redundant computer systems onboard.

  9. Yup. The Voyager 2, which is now 8.5 billion miles out (twice the distance from the moon to Pluto), is run by a CPD1802. So was the COSMAC ELF computer that I build around 1979 from a Popular Electronics construction article. A great little processor. My self-designed OS took about 60 bytes, my memory dialer program about 68 bytes, and the data another 128 bytes for a total of 256 bytes of RAM.

  10. A teacher once told us the golden rule for his class was KISS (Keep It Simple, Stupid!). Sounds like KISS applies in this case. I’d heard of this before–I think the computer simply controls the thrusters on re-entry. There is probably more risk in upgrading it than not.

    I believe you’re right in some sense, but other times, having to save a few cpu cycles or memory access means jumping through various hoops, and in the end this can result in complex code.

  11. The computers on the space shuttle do not have to play video games which require more powerful hardware every year.
    They just needed basic graphics and trajectories.(the space capsules got it right).

  12. Nasa confirmed that the next Space Shuttle Computer system will be built using AMD Phenom II Quad processor and ATI Radeon 5790 graphics card supporting DirectX 11

    The Control console of shuttle will be fully GUI. As there is a wait time before astronauts get into space after liftoff, NASA ha splanned ot load some recreational games such as COD WM 2 so astronauts can play them while sitting ideal

  13. Outer space is not friendly to semiconductors. Cosmic rays just love to wreak havoc with electronics. The smaller the circuit pathway is, the more susceptible to damage and failure it is.

    So, all of that fancy schmancy high speed silicon you have in your gaming PC is more likely to be turned into worthless Swiss cheese by sub atomic particles traveling near the speed of light than an old, but reliable set of circuits with a large per-transistor footprint on a wafer.

    Think of it this way, placing an Intel Core i7 at 3.3GHz and 16 GB of RAM in space is the same as placing a Ferrari in a monster truck rally.

  14. My first computer ran 4mb ram and 100mb hard drive in 1995. I designed complex websites. I used to have to write the code, shut down notepad and open Netscape to check it, then shut down Netscape and open notepad to make changes. Multitasking at its best!

  15. Guessing your site gets a lots of visitors since the design is professional. Who’s your designer is? Feel free to email me.

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