Space travel does not always require warp-speed innovation

How powerful were the Apollo computers?

Would you travel to the moon in a vessel equipped only with a Radio Shack TRS-80 computer or a Commodore VIC-20?

The astronauts of the Apollo missions used computer technology that's primitive by today's standards. But as our reach and power into space have expanded — think probes to distant planets, space telescopes, the space shuttle program and the International Space Station — remnants of the old technologies are still in use.

"To this day, NASA still uses elements of technology that powered the moon landings of the 1960s and 1970s, while the International Space Station — the manned station circling the Earth 250 miles above our heads — relies on processors dating back more than two decades," writes Nick Heath at

The space shuttle program has seen only one major upgrade to its avionics computer technology since the program's inception in the 1970s, Heath adds.

Alessandro Donati, head of the Advanced Mission Concepts and Technologies Office at the European Space Agency's Space Operations Centre in Darmstadt, Germany, told Heath that the important factor for space exploration IT is reliability, not innovation.

"In aerospace, you don't fly the cutting-edge technology that is being used on the ground by business," Donati said.

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Look at how primitive this seems, and recall that the Apollo program used computers developed 15 or 20 years earlier.

The computer that provided flight guidance for the Apollo missions was so simple that a hobbyist can now build one at home, according to a design from John Pultorak.

The Apollo guidance computer pales in comparison to even the first-generation IBM PC, which at 8K had four times as much memory and a processor that ran at 4.077 MHz, compared with the Apollo computer's 1.024 MHz, writes Grant Robertson at

"The real-time operating system in the Apollo 11 spacecraft could multitask eight jobs at a time, no small feat for the time it was developed and something we take entirely for granted today," Robertson writes. "Multitasking, however, wasn't quite as we now think of it. Today's operating systems use mostly preemptive multitasking, where the operating system itself is in control of the execution and can stop any program at any time and hand off some computing power to another. The Apollo Guidance Computer relied on non-preemptive multitasking, whereby programs had to relinquish control back to the OS periodically. "

This is not to say that NASA relies on primitive technology. The Apollo computers were cutting-edge for their time, and NASA today pioneers the use of supercomputers for space science.

It is a marvel, though, that something as precise and daring as sending men to the moon, landing them, coordinating a rendezvous with their command module for the ride home and bringing the craft to rest in the ocean with enough precision for surface ships to reach the spot quickly could be done with less computing power than we can today hold in the palms of our hands.

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Reader Comments

Mon, Oct 4, 2010 Eugene, OR

The Space shuttle program currently uses a mil-spec version of the 6502 processor. The main reason for not updating this is because the exact behavior of any code running on this processor and changing environmental conditions are precisely known. As others have stated radiation and other environmental conditions are factors that can not be ignored. The system also has a total of 4 processors running at all times they run on a 2/3 vote system so that if any processor does not agree with the others it is shut down. If only two are functioning the mission could be aborted. We can not afford to have a processor reboot or lock up when in the middle of a launch or reentry sequence or other mission critical functions. Systems can be very fast and efficient running well developed machine code(something most of us don't remember) I remember writing control code for a 6800 processor with only 256 bits (yes thats bits not Bytes) of memory to store the whole program in.

Mon, Oct 4, 2010 Don Largo, FL

Anyone interested in getting the background scoop on the Apollo 11 Guidance Computer, should read this:


Another aspect not taken into account in this article is that it is not easy to upgrade older legacy systems with the hardware, you can't just slap in a new computer system and say "tadaa". I have seen this problem in the defense sector as well. Good example is the Pave Paws Early Warning Radars were built in the early 70's with state of the art main frame at the time. They only recently got rid of the main frames and upgraded to new systems in the last couple of years and the inherent difficulty in the upgrade was in bridging the gap with servos, sensors, commo ports, etc. All that stuffed had to be built from scratch to interface the systems together.

Fri, Oct 1, 2010 Brian

I think some rapid innovations for space travel are still required to take us to other planets.

Fri, Oct 1, 2010 Cris Washiongton, DC

You failed to point out the primary reason for relying on seemingly antique processors for space bound computers – radiation. The closer the traces on the processor become the more susceptible the processor and memory chips become to radiation damage and spurious operations caused by high energy particle impingement. The old 386's were bricks by comparison to ‘modern’ processors and memory, but very radiation tolerant. The only thing worse then an old processor is a new processor that doesn't work where you need it to work.

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