Chair Force Engineer

Thursday, December 24, 2009

A Nerd's All-Time Favorite Christmas Gift

This Christmas Eve I wanted to reflect on the best Christmas gift I've ever received, because it's one that my nerdier readers will draw common cause with. While action figures had a shiny newness and appeal that always brought me excitement on Christmas morning, they were never fascinating enough to hold my interest much longer after Christmas. Instead, my all-time favorite Christmas gift was the Nintendo Entertainment System that my brother and I received exactly 20 years ago today.

Neither of us had asked for a Nintendo, but the gift wasn't unexpected. After all, one of my favorite cartoons from the time was The Super Mario Brothers Super Show, starring the late Captain Lou Albano. I vividly remember opening the box and watching my father set the system up. He got us started on the pack-in game (Super Mario Bros/Duck Hunt/World Class Track Meet) and the dreadfully-frustrating Ghostbusters. I was immediately impressed by the vivid colors and 8-bit "orchestra" of synthesized sound. (Kids must have been so much easier to impress back in 1989.) I always wanted to kill the laughing dog from Duck Hunt, but the stupid game would never let me. From that point on, I was a Nintendo junkie (in spite of my conversion to Playstation by 1996.) But the NES was one of the most thoughtful and most enduring Christmas gifts I have ever received.

Nintendo's introduction of the NES with a limited launch for Christmas 1985 was nothing short of a stroke of genius. They launched the system against staggering odds precluding their success. The video game industry was dying, thanks to a flood of powerful, low-cost computers (especially the Commodore 64,) a glut of unimpressive games (epitomized by E.T. and Pac-Man on Atari 2600) and oversized, unreliable game systems like Atari 5200. Nintendo took a two-pronged approach: the NES would be designed to resemble a VCR and other commercial electronics instad of a video-game "toy," while the R.O.B. robot peripheral would position the NES as a toy that didn't have to compete toe-to-toe with Atari. I really can't say which of these factors drove the masses back to video games in the form of NES, but the schizophrenic approach worked.

As the NES rose to dominate the video games market, Nintendo started practicing some anti-competitive business tactics whose benefit to their market share was questionable in the long run. Since a deluge of bad games brought on the video game crash of 1983, Nintendo limited the number of games each game publisher could release per year, and Nintendo manufactured all officially-licensed cartridges in-house. Game publishers were barred from porting their NES games to other systems for two years after their NES releases, which hurt upstart console manufacturers like Sega. (Sega eventually overcame this hurdle with an impressive lineup of games that were developed in-house for their Genesis console.) Nintendo eventually eased up when it noticed the success of the upstart Sega Genesis, which was a marked improvement over the outdated NES. It finally motivated the video games giant to produce the Super NES as a competitor to the "edgier" Genesis console.

Nonetheless, video games will always be an important part of my childhood and even my adulthood. Last night I gave my girlfriend a Nintendo Wii, rekindling some of the memories I had of the magical Christmas of NES. Wii is no powerhouse compared to competing video game systems, but its motion sensitive control makes it a completely different (and very immersive) gaming experience. For good measure, I asked her to play Super Mario Bros. on Wii's Virtual Console for old times sake. Needless to say, I'm almost as bad at Mario games as I was 20 years ago. But the challenge and fun that were perfected on NES are timeless and constant.

Tuesday, December 15, 2009

Flight of the Plastic Airplane

I just finished watching the video from the Boeing 787 first flight. The takeoff of an airliner is a mundane sight, yet it's such a beautiful moment for everybody (including friends of mine from college) who poured themselves into the program. The elegant airplane with its caverous engine nacelles and dihedraled wings soared from the runway on a short jaunt to test the major systems, hopefully ushering in a new era of air travel.

I often joked that the 787 would never fly, since this test flight had been delayed for over two years. Today I eat my words. While the 787 doesn't break any bold new ground in terms of what airliners are supposed to look like (especially when compared to the radically-sleek 787 concept art that was released in 2004 when the program launched,) it's a drastic departure from a materials standpoint. No commercial airliner has ever flown with such a high percentage of its airframe made from composite materials. For this reason, it's been affectionately dubbed "the plastic airplane." (It's just a nickname, and not a false comparison between composites and plastics.) The extra two years were necessary to ensure this moment would be a success for such a revolutionary bird. When a disgruntled Boeing engineer went public in September 2007 claiming the plane's composite fuselage would shatter during a belly landing, it made me stop to think of the ingenuity that was required to solve the problem. (I dismissed the engineer's claims, since the FAA would never certify the plane if they were true.)

Here's to hoping for a bold new future of composite airframe structures and lower fuel consumption per seat-mile. Thank you, Boeing 787 team, for getting us closer to that dream.

Friday, December 11, 2009

Thoughts About Rocket Reliability

Much has been written in great detail about the reliability of launch vehicles. In the case of the Space Shuttle, the Loss-of-Mission probability of 1:100,000 (promoted by NASA management prior to the loss of Challenger) has turned into an empirical probability that greater than one-in-65 shuttle missions would result in loss of crew and vehicle.

Theoretical and empirical probabilities are two very different animals, especially when it comes to launch vehicle failure rates. Elon Musk had once boasted something along the lines of "Falcon I would be the most reliable rocket vehicle ever produced." On paper, he was correct. There were only two stages, one of which was powered by a simple, pressure-fed and radiatively-cooled engine. When adding up all of the probabilities of different failure modes, the vehicle has an extremely low probability for loss-of-mission. But there are so many factors to consider when identifying failure modes. When the consultants at Aerospace Corporation computed the odds of Falcon I failure, did they look at things like corroded nuts on the first stage, sloshing in the second stage, or unexpected transients with the upgraded Merlin engine? The last of these three problems (which doomed the first three Falcon missions, respectively) was certainly neglected in the analysis of the original Falcon configuration.

Failure probabilities rarely take into account the factor of human error. In the case of Challenger, the failure probability quoted by NASA management never took into account the lack of data about SRB joint behavior in extremely cold weather conditions. In Challenger's instance, managers on the NASA and SRB contractor side exercised criminal stupidity in violating established flight rules. Should risk assessments take the probability of criminal stupidity into account?

Ares I is supposed to be "Safe, Simple and Soon." ATK can justify their slogan by pointing to the booster's solid-fuel first stage. As at least one shuttle astronaut has said, "Once the SRB's light, you know you're going somewhere." SRB's have very reliable ignition systems. The probability of a single SRB failing at ignition are very low, hence the claims from ATK and NASA (which will certainly be inflated when compred to the empirical data that will come from a real, flying Ares I) that this is the safest manned launch vehicle.

Yet the reliability of Ares I's ignition system is not necessarily a boon when compared to other launchers. SpaceX's Falcon series holds down the booster for a short period of time after engine ignition to verify the health of the engines. The booster is only released after SpaceX's launch team is certain that the vehicle is healthy. Even the shuttle has a similar hold-down, igniting the liquid engines first and verifying their health before lighting the SRB's which provide the thrust for liftoff. But once the SRB's ignited, there's no way the team at the Cape could have held Challenger back for some kind of health check to establish the integrity of the SRB joint seals.

In the case of Falcon 9, the nine engines may seem to multiply the probability of a failure ruining your launch day. Yet the step of verifying engine health on the pad reduces the probability of a fatal engine failure early in ascent. As the vehicle climbs and burns off fuel, it can afford to lose engines and still have enough thrust to achieve orbit. The system is akin to an airliner testing its engines on the ground, yet it can afford an engine failure during the cruise portion of the flight.

Flight International's Rob Coppinger reports that Atlas V was deemed unsafe for manned spaceflight during the Orbital Space plane program, at least in its variant with three SRB's attached to the first stage. Politically, there may be good reasons for disqualifying Atlas V (the Russian-produced main engine.) From a safety perspective, the addition of SRB's does create more failure modes and increase the statistical probability of launch failure. (It would seem that NASA rejects the idea of one liquid engine plus three solids as unsafe, even though the shuttle's three liquid engines and two solids are perfectly fine.) But that's not to say the entire Atlas V family is inherently unsafe. Statistically speaking, the simplest Atlas (the 401 variant, with one first stage engine and one second stage engine) is the safest; it wasn't considered for the OSP program because the SRB's were necessary to lift OSP's mass. For a smaller capsule, Atlas V may meet stringient safety requirements.

The big idea is that there's a vast different between wildly optimistic estimates of reliability (based on mathematical equations that often neglect major failure modes) and empirical failure rates that are established once a vehicle has flown. I remain optimistic about the human-rating potential for Delta and Atlas because both vehicles have flight histories without a failure that ended in loss of mission. (There was the Delta IV Heavy partial failure and the Atlas V partial failure that resulted in lower orbits for their payloads, but nothing that would have killed a crew.) Falcon I seems to be on the right track for a reliable launch record now that the problems have been ironed out. Falcon 9 can hopefully reuse the flight-tested Falcon I hardware and establish a similar reliability.

Ares I creates tremendous unknowns from a reliability standpoint. Due to the size of the explosion after range safety destroys the vehicle, any kind of first stage failure (even a control failure) should be regarded as unsurvivable for the crew. (I may revise my judement on this matter once more detailed, independent analysis of the problem is complete.) Virtually none of the Ares I hardware has any empirical probability data that comes from flight history, in spite of the smoke and mirrors act known as "Ares I-X." Hopefully the Ares guys know what they're doing, but my gut tells me that Ares, like Shuttle, will be a tragic disappointment once the vehicle's safety is truly known.