Chair Force Engineer

Wednesday, August 24, 2011

$pace Launch $ystem

The Ares family of NASA rockets isn't dead. It lives to fight another day under new names. Ares I has already been reborn as "Liberty," a private ATK-Astrium joint venture. The Ares V heavy-lifter on the other hand, is now the Space Launch System.

As currently envisioned, Space Launch System resembles the original Ares V design from the ESAS report in summer and fall of 2005. The core rocket is the same diameter as the shuttle's external tank, and the core engines are based on the Space Shuttle Main Engines. Obviously, NASA's design engineers must have revisited the assumptions that were made when they switched Ares V to a new, wider-diameter core and less-efficient (but cheaper) RS-68 engines.

The advantages of reusing shuttle-heritage boosters, core engines and propellant tanks aren't as obvious as one might expect. Most of the components are being placed under very different aerodynamic and mechanical loads compared to what they saw under the shuttle program, so the testing will need to be repeated. Reusing shuttle manufacturing tools and launch facilities will result in some cost savings, but the development costs will be similar to what should be expected for an all-new heavy-lift rocket.

In fact, a recent report by Booz Allen Hamilton (hat tip: Hobbyspace) questions NASA's accounting for what SLS is really going to cost. It cites NASA's optimistic estimates for future cost savings. Without seeing this report, I can speculate that it's referring to the costs associated with using expendable versions of the shuttle main engine on every flight.

Besides the costs, it's foolishly optimistic to beleive NASA's estimate of an SLS test launch by 2016. Consider that the Saturn V was approved in January 1962, but didn't make a test flight until November 1967. So a well-funded heavy-lift program should expect to take at least 5 1/2 years from the moment it receives authority to proceed. But we shouldn't expect development to proceed at such a breakneck pace as Project Apollo (during an era when NASA registered at over 1% of the federal budget.) Unless Congress shovels large sums of development & test money at SLS, the schedule will likely slip by several years.

Complicating the situation is the wrangling over side-mount boosters for SLS. The baseline calls for the five-segment SRB's that have been largely developed by ATK. NASA administrator Charlie Bolden wants to open up a competition to build new boosters for SLS. Such a competition would likely produce a better-performing, better-value booster for the taxpayers--or at least serve as a check against cost growth on the ATK boosters. But opening up the booster trade-space adds to the SLS schedule.

The SLS budget and schedule will be an important issue for NASA over the next few years, but it will likely be overcome by events. SpaceX will fly its Falcon Heavy by 2014, perhaps 2015 given the inevitable schedule slips in complex development programs. While Falcon Heavy does not have the heavy-lift capabilities of SLS (50 metric tonnes versus 130 mT,) it doesn't need them if on-orbit assembly and propellant transfer become accepted means of sending humans on deep-space missions. In 2015 or 2016, Falcon heavy will be flying while SLS will still be a year or more from its first test. For a budget-conscious Congress, SLS will make a ripe target for cancellation and cost savings.

Saturday, August 13, 2011

Air Force Research Linux

One of the best selling points for the Linux operating system is its small footprint in your computer's RAM, hard drive, and overall system requirements. Linux distros like Puppy Linux and Damn Small Linux (the latter no longer updated) have been tailored to run on very old PC's (Pentium 3 for the former, Pentium 1 for the latter) and capable of residing entirely in RAM. Running a lightweight Linux can keep older PC's relevant for most people's internet needs.

But a new and surprising player is jumping into the lightweight Linux game--the US Department of Defense. Developed by Air Force Research Laboratory, Lightweight Portable Security (LPS) is a Linux distro that resides completely in RAM, with no option of mounting the hard drive or writing to it. The logic behind LPS is that malware cannot be written to DoD computer systems since the hard drive cannot be engaged.

The "lightweight" part of the name is a bit of a misnomer. LPS requires 512 megs of RAM for the basic OS, and 1 gig of RAM for the deluxe version which includes the productivity suite. And the deluxe version did seem a bit slower than Puppy Linux when it booted.

But in spite of being not-so- "lightweight," LPS does have a great feature going for it. LPS can auto-detect a broad range of hardware and automatically load the appropriate drivers. I would even say that LPS is better than the "heavyweight" Linux distros in this regard. Of all the distros I've tried, only LPS instantly recognized my laptop's internal wireless adapter. Then again, not all the drivers are very well-written; my laptop's touchpad acts very flaky in Firefox.

With the key features and drawbacks to LPS in mind, who is the target user? The LPS website mentions booting it from a flash memory device, even though that storage method is banned on all DoD network computers. It would instead seem that LPS is a means for DoD personnel to check e-mail and do limited work from home or while on business travel.

Overall, using LPS has been a fun experience. If I ever needed to check my business webmail from the computer in the hotel lobby, LPS would be the way to do it. For people who want a real lightweight Linux I would recommend downloading Puppy Linux, installing it to the hard drive of their aging PC, and downloading the extra goodies that LPS deluxe boasts, like All flaws aside, LPS is definitely worth a download. All it takes is a few minutes to download and a single recordable CD to surf the web, LPS-style.

Friday, August 12, 2011

Death of the World's Fastest Airplane*

The Defense Advanced Projects Research Agency (DARPA) launched the second and last of its HTV-2 hypersonic test vehicles yesterday, in what some media outlets have labeled "the world's fastest airplane." It's true that the HTV-2 skirted the atmosphere at Mach 20 once separated from its Minotaur IV booster rocket, so it might be the world's fastest unpowered glider. But the same could be said about the space shuttle. Like the shuttle, HTV-2 maneuvered while in a hypersonic glide, partly to bleed off excess airspeed.

Disappointingly, HTV-2's flight ended about 10 minutes short of what was expected. After 20 minutes, DARPA reported that they had lost telemetry. The most likely scenario? Somewhere during gliding flight, the vehicle disintegrated. Even after 30 years of shuttle flights and countless other rocket-plane programs before that, controlled hypersonic flight is still difficult. Unlike a ballistic vehicle like a space capsule, a winged vehicle has to maintain active control during flight. The aerodynamic stresses at such extreme speeds are high, and the unbelievable heating of the aircraft's structure causes it to lose much of its inherent strength. Even a small deviation from a safe flight attitude can destroy the aircraft. This is what happened as space shuttle Columbia began to encounter increased drag on its damaged left wing, with the orbiter's thrusters trying in vain to correct the unexpected yaw until they could no longer prevent the shuttle from breaking apart. DARPA will probably reach a similar (albeit more detailed) conclusion after analyzing all of their telemetry from the mission.

Several years ago, HTV-2 was supposed to be a stepping stone to what the defense department called "FALCON," or Force Application & Launch from Continental US. The idea was to strike a time-sensitive target so rapidly that there would be no way to avoid the attack. But existing ballistic missiles weren't acceptable because they would startle Russia or China into thinking we were launching the nuclear ICBM's. FALCON aimed to create hypersonic gliders and eventually a hypersonic bomber to meet the goals of rapid global strike. Apparently a straight-up launch of the glider on a converted ICBM (like Minotaur IV) would not give the other nuclear powers a false alarm. But now the idea appears to be dead, for lack of results and funding.

The basic idea of a hypersonic glider has been studied exhaustively since the 1950's. As the whims of the military and political leadership change, the FALCON concept may get a fresh look.

Friday, August 05, 2011

An Atlas-Kinda Day

For the Atlas V launch vehicle program, today was a big day. The first major development was the successful launch of the Juno space probe which will study the planet Jupiter. When I heard that Juno was being launched into space, I first had to wonder whether Michael Cera would be lonely back on earth. But all kidding aside, Juno will study our solar system's largest planet in the 2016-17 time frame and hopefully tell us more about the formation of a planet that we've come to think of as a failed star. In some ways the probe is a "consolation prize" for the failed Jupiter Icy moons Orbiter, which would have used a nuclear reactor to power its ion engines. The science mission is very different, though, and the moons of Jupiter will sadly need to wait before their secrets open up to us.

The other exciting Atlas-related development was Boeing's decision to fly its CST-100 manned spacecraft on Atlas V rockets. It's interesting to note that they will be using an Atlas V 412--four-meter diameter fairing, one solid rocket booster, and two engines on the upper stage. This configuration increases the thrust margins for manned spaceflight, which is especially important when the rocket is flying the shallower trajectories which allow for successful crew escape. Having one SRB does create a small increase in the probability of first stage failure, but that's mitigated by the crew escape system that will be present while the SRB is burning. Also interesting is the two-engine upper stage. As far as I know, this is the first Atlas V payload to request two upper stage engines. The addend engine does give the astronauts some extra redundancy if one fails, although the RL-10 eries engines on the Centaur upper stages have been pretty reliable (dating all the way back to 1962.)

When manned flights of CST-100 and Atlas V start in 2015, it will be interesting to see how Boeing selects its crew of two astronauts (or "test pilots," as Boeing calls them.) They will likely choose from former astronauts who have gone to work for the Boeing company. (And there's at least one cosmonaut who works for Boeing, IIRC.) I'm certain that "astronaut" would be an interesting job listing to find on It remains to be seen on when the operators of privately-owned manned spacecraft start to hire new astronauts with no previous spaceflight experience. There's no reason to think that NASA's rigorous requirements will be eased for the private astronauts.

Monday, August 01, 2011

War of the Operating Systems (Part 2)

Success! This blog is being updated from my 2001-vintage Power Mac G4 again, but this time running Xubuntu 6.10. If you still "bitterly cling" to PowerPC Macintosh hardware, it's becoming increasingly rare to find a suitable Linux distribution. Most of the major distros (Ubuntu, Debian and openSUSE come to mind) have either dropped support for PowerPC, or support it erratically from release to release. And when they do offer PPC support, the distro often takes up a full DVD--little use to owners of systems that were built before DVD's came standard with most computers.

My first attempt at PPC Linux was Debian 6.0.1, but it didn't seem to support the ATI Advanced Graphics Port video display in my system. (I found it funny that the Debian installer didn't even quiz me to select my video card from a list of choices.)

After two attempts and staring at a screen that was a garbled, frozen mess of black and gray, I looked into the other Linux distributions. Xubuntu 6.10 (from back in 2006) was the last Xubuntu release I could find that supported PowerPC. And it conveniently fit on a single CD. Besides, the Xfce lightweight desktop seemed to be a good fit for a system that currently has only 256 MB of RAM. The install process was a little bit slower than I expected, but in the end I got a working system with a clean (albeit simple) interface and very little lag. And I didn't need to resort to anything crazy like buying a new DVD drive to install in a system that cost me all of $30 to purchase.

Even with the Xfce desktop environment, Linux on the PowerMac seems sluggish in comparison to MorphOS. Maybe the situation would have been different if Linux was written from the ground-up to run on PowerPC as MorphOS was. But I'll still probably use this system almost exclusively for Linux, since Linux has a pretty good selection of software written for it. Eventually I intend to host a website from this system.

On a side note, I've also attempted using one last OS: Dragonfly BSD. It's a fork of FreeBSD with some ideas taken from the old Commodore Amiga's OS. And I say "attempted" using it, because the disk images I've burned all appear to be corrupt. Perhaps someday it will be worth a try, as the BSD family has a very strong base of users who swear by its stability and its usefulness in applications such as web servers.

Now that I've succeeded in getting Linux on the old PowerMac, I don't intend to end my flirtation with non-Windows, non-Mac operating systems. I do hope to revisit the subject in a future post with a more detailed comaprison, and perhaps some commentary on newer Linux distributions.