Deploy Workaround Code To The Field When “The Field” Is Lunar Orbit

February 3, 2020 by Roger Cheng 6 Comments

The Apollo missions still inspire people today, decades after they took place. A fortunate side effect of the global public relations campaign is that a lot of information is publicly available for us to review and process. We’re right around the 49th anniversary of Apollo 14 mission, so it was a good time for [Frank O’Brien] to take readers through Apollo Guidance Computer and the hack that saved Apollo 14 (while it was in lunar orbit).

Space fans would already know many parts of this piece, but [Frank] weaves it together into a single narrative around a problematic “Abort” button that was found to be making intermittent contact as the crew were preparing to land on the moon. An inconvenient timing would have unnecessarily aborted the mission, which was obviously Not Good. [Frank] brings us up to speed on AGC fundamentals, just enough to understand the technical constraints for the hack, devised within the time constraints they faced.

For those that prefer a short video summary [Scott Manley] covered this same hack on YouTube. And for another perspective on the scope of this task, remember this was years before we had vi or emacs. When they were contemplating flipping status bits as programs were running, it’s not trivial to do a global search for code that might examine those bits. Look at the tome of source code AGC programmer [Don Eyles] worked with. Space fans who want to learn more can check out [Don]’s book.

For the ultimate AGC talk, check out The Ultimate AGC Talk.

Maybe someday trips to the moon will be a commonplace thing, but Apollo will always be the pioneer.

A SpaceX Falcon 9 Will Blow Up Very Soon, And That’s OK

January 16, 2020 by Tom Nardi 27 Comments

They say you can’t make an omelette without breaking a few eggs, and there are few fields where this idiom is better exemplified than rocketry. It’s a forgone conclusion that when you develop a new booster, at least a few test articles are going to be destroyed in the process. In fact, some argue that a program that doesn’t push the hardware to the breaking point is a program that’s not testing aggressively enough.

Which is why, assuming everything goes according to plan, SpaceX will be obliterating one of their Falcon 9 boosters a little after 8:00 AM EST on Saturday morning. The event will be broadcast live via the Internet, and thanks to the roughly 70% propellant load it will be carrying at the moment of its destruction, it should prove to be quite a show.

This might seem like an odd way to spend $62 million, but for SpaceX, it’s worth it to know that the Crew Dragon Launch Abort System (LES) will work under actual flight conditions. The LES has already been successfully tested once, but that was on the ground and from a standstill. It allowed engineers to see how the system would behave should an abort occur while the rocket was still on the pad, but as the loss of the Soyuz MS-10 dramatically demonstrated, astronauts may need to make a timely exit from a rocket that’s already well on the way to space.

In an actual emergency, the crewed spacecraft will very likely be speeding away from a violent explosion and rapidly expanding cloud of shrapnel. The complete destruction of the Falcon 9 that will be carrying the Crew Dragon during Saturday’s test will serve to create the same sort of conditions the spacecraft will need to survive if the LES has any hope of bringing the crew home safely. So even if there was some way to prevent the booster from breaking up during the test, it’s more useful from an engineering standpoint to destroy it.

Of course, that only explains why the Falcon 9 will be destroyed during this test. But exactly how this properly functioning booster will find itself being ripped to pieces high over the Atlantic Ocean in a matter of seconds is an equally interesting question.

Continue reading “A SpaceX Falcon 9 Will Blow Up Very Soon, And That’s OK” →

New Space Abort Systems Go Back To The Future

July 15, 2019 by Tom Nardi 26 Comments

Throughout the history of America’s human spaceflight program, there’s been an alternating pattern in regards to abort systems. From Alan Shepard’s first flight in 1961 on, every Mercury capsule was equipped with a Launch Escape System (LES) tower that could pull the spacecraft away from a malfunctioning rocket. But by the first operational flight of the Gemini program in 1965, the LES tower had been deleted in favor of ejection seats. Just three years later, the LES tower returned for the first manned flight of the Apollo program.

With the Space Shuttle, things got more complicated. There was no safe way to separate the Orbiter from the rest of the stack, so when Columbia made its first test flight in 1981, NASA returned again to ejection seats, this time pulled from an SR-71 Blackbird. But once flight tests were complete, the ejector seats were removed; leaving Columbia and all subsequent Orbiters without any form of LES. At the time, NASA believed the Space Shuttle was so reliable that there was no need for an emergency escape system.

It took the loss of Challenger and her crew in 1986 to prove NASA had made a grave error in judgment, but by then, it was too late. Changes were made to the Shuttle in the wake of the accident investigation, but escape during powered flight was still impossible. While a LES would not have saved the crew of Columbia in 2003, another seven lives lost aboard the fundamentally flawed Orbiter played a large part in President George W. Bush’s decision to begin winding down the Shuttle program.

In the post-Shuttle era, NASA has made it clear that maintaining abort capability from liftoff to orbital insertion is a critical requirement. Their own Orion spacecraft has this ability, and they demand the same from commercial partners such as SpaceX and Boeing. But while all three vehicles are absolutely bristling with high-tech wizardry, their abort systems are not far removed from what we were using in the 1960’s.

Let’s take a look at the Launch Escape Systems for America’s next three capsules, and see where historical experience helped guide the design of these state-of-the-art spacecraft.

Continue reading “New Space Abort Systems Go Back To The Future” →

The Longest Tech Support Call: Apollo 14 Computer Hack

September 21, 2017 by Al Williams 12 Comments

Deep-voiced and aptly named [Scott Manley] posted a video about the computer hack that saved Apollo 14. Unlike some articles about the incident, [Scott] gets into the technical details in an entertaining way. If you don’t remember, Apollo 14 had an issue where the abort command button would occasionally signal when it shouldn’t.

The common story is that a NASA engineer found a way to reprogram the Apollo guidance computer. However, [Scott] points out that the rope memory in the computer wasn’t reprogrammable and there was no remote way to send commands to the computer anyway.

Continue reading “The Longest Tech Support Call: Apollo 14 Computer Hack” →