Chair Force Engineer

Saturday, September 17, 2011

DIRECT to Triumph

NASA was grabbing headlines this past week with plans to build the most powerful rocket to ever lift off the earth. The Space Launch System is expected to be operational by 2017, with an Orion capsule riding atop an 8.4-meter core stage and flanked by two 5-segment solid rocket boosters. A later variant will have an upper-stage to place massive payloads up to 130 tons into orbit. At least that's what happens if all goes according to plan.

Pieces of shuttle hardware live again; Space Launch System reuses the barrel sections and domes from the External Tank (larger propellant feed lines will be necessary for the heavy-lift variant.) The main propulsion system comes from the shuttle orbiters, including the Space Shuttle Main Engines. Three will be mounted on a diagonal for the crew-launch variant, and five will be mounted in an "X" for the heavy-lifter. Spare engines from the shuttle will be used on early missions, but Pratt & Whitney Rocketdyne will redesign the nozzle and other components to make the engines cheaper to produce and throw away on future flights. And for initial flights, the rocket will use 5-segment SRB's developed for the original Ares program.

A significant part of the Space Launch System announcement is that it's a declaration of victory for the DIRECT team. Since the end of 2006, DIRECT has been agitating for a return to a shuttle-based system as the Ares rockets underwent a death-spiral of requirements creep and weight growth. It was the first proposal I'm aware of that used a flexible system to mount engines to the core stage, using an appropriate number of engines for the mission. They popularized the concept of using the heavy-lifter, sans upper stage, to launch a manned capsule. By the time of DIRECT 3.0 in May 2009, the team had embraced the use of expendable SSME's to get maximum performance out of the propellants stored in the core stage. Aside from one aspect, the rocket proposed for SLS is DIRECT.

The biggest difference is in the solid rocket boosters. Back in 2006, the DIRECT team wanted to use the stock 4-segment SRB's from the shuttle. The idea made sense back then, when NASA had barely begun their development. But the 5-segment stretched SRB got a significant portion of NASA spending during Project Constellation, to the point where it wouldn't be much more expensive to make the switch now that most of the development costs have been sunk. So SLS is using the 5-segment solids on initial missions, with rocket vendors free to develop alternative boosters for future variants of the rocket. The shuttle tankage at the core of SLS has been stretched to accommodate the attach points for the longer boosters.

Will SLS be built? I'd give that prospect a 50-50 shot. The program will receive a development budget of $3 billion per year for the next several years, fitting into the budget wedge once occupied by the Space Shuttle program. In earlier times that would not have been a problem for the federal government, but these are now times of austerity. And if SpaceX will have their 53-ton launcher flying by 2014-5, it will be hard for NASA to justify their 74-ton launcher by 2017. If Congress does keep SLS alive, the ulterior motive will be providing a stimulus to the tech industry to keep good jobs in Florida, Alabama and other states that figured heavily into the Space Shuttle program.

The tragedy of Project Constellation is that SLS is virtually the same as the original Ares V rocket, specified by the ESAS report in summer and fall 2005. Great sums of money have been spent and little real progress was made in developing the rocket's core or its ground facilities. The death spiral started in early 2006 when NASA adopted RS-68 engines for the core of Ares V. RS-68 was cheaper to produce and throw away than SSME, but it burned fuel less efficiently. Unwilling to sacrifice the monster rocket's performance, NASA widened the tank to 10 meters diameter. This meant a major redesign of the Mobile Launch Pad, the need for new crawler-transporters, and possibly even changes to the crawlerway and hardstand at the launch site to shore it up. The entire rocket was so heavy that NASA needed a sixth RS-68 under the core. And nestled between the plumes of two SRB's, the RS-68's were being exposed to far greater temperatures than their ablative-cooled nozzles could handle. Ares could either switch back to SSME, or pay for a new regeneratively-cooled nozzle on the RS-68. Such was the state of the program before it was euthanized in February 2010.

Did the DIRECT guys do any breakthrough, original engineering analysis to show why their idea was better? No. They simply kept in touch with the engineers within NASA who knew that Ares V was doomed to fail as long as the program continued marching towards unachievable payload masses and without regard for development budgets and schedules. The final SLS design probably owes much more to NASA engineers saying "You know what? Our original Ares V design wasn't so bad, and it could have worked if management didn't start messing with it." But in the spirit of maintaining an independent sanity check, the DIRECT team should be proud of keeping a viable idea alive and within the view of policymakers, while NASA kept chasing an ever-growing Ares V down a rabbit hole.

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







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.

Sunday, July 31, 2011

War of the Operating Systems (Part 1)

Back when I was young and starting to use computers on a daily basis, I read a lot of computer pundits who bashed Microsoft Windows. Naturally, I began to parrot their point of view. It seemed logical; after all, Windows 95 crashed all the time whenever I needed to use it. During my teenage years I began my search for a different operating system that would cost less than Windows, still support my hardware, avoid the annoying crashes that I saw under Windows 95, and offer up all the applications that I needed to play games, type documents, surf the internet, and all of the other things I used my computer for.

My early attempts to use Linux (particularly Red hat and Caldera) quickly ended with my frustration as they didn't support my hardware. Perhaps with a bit of tweaking I could have gotten them to work, but at that age I didn't have the time or expertise.

By the time I gave up on Linux, Microsoft was finally getting its act together. After Windows 98 cynically attempted to force Internet Explorer on everybody, Microsoft started anew with Windows 2000 and XP. They were built from the ground up as 32-bit OS'es, not a kludge of 32-bit Windows plus 16-bit DOS. And Microsoft supported them vigorously with service packs and other handy features to repair corrupted systems. So until Windows Vista was released ("defecated" might be a more appropriate term for the turd-ish Vista,) I regained a lot of respect for what Microsoft was doing. Windows might not be the most stable OS, but it installed properly 99% of the time and supported a mind-boggling number of hardware configurations. Not to mention that all of the most popular software titles were written for it.

But a lot had changed in the Linux world since the last time I tried it, too. Corporations like Novell and Oracle had invested serious money into making Linux a viable OS for desktop computers. (Not to mention the revolution called Ubuntu, launched by space tourist Mark Shuttleworth in 2004.) So I've dabbled with Linux lately and succeeded in getting OpenSUSE 11 to work on a 2006-vintage PC.

But I wasn't content to stop at Windows in my desire to tinker. I bought a used Power Mac G4 so I could try MorphOS, a lightweight OS for Power PC computers that's compatible with the old Commodore Amiga. The MorphOS team wisely chose to develop their OS for a limited set of hardware that had been mass-produced; namely, Macintosh computers with G4 processors. I have installed and used MorphOS, and it's worked reliably every time for me. And MorphOS doesn't suffer from slowdown, even on a system with only 256 MB ram and a 13 GB hard drive. (In fact, I'm typing this blog post on my MorphOS machine right now.) The biggest drawback is that very few popular software titles have been ported to MorphOS, and I'm not compelled to pay over $100 to unlock the full version of MorphOS until programs like OpenOffice and GIMP are available.

I still want this old Power Mac to run Linux in a dual-boot setup with MorphOS. I tried installing Debian Linux 6 today and it failed miserably on this machine. So plan B is to try OpenSUSE 11.1 (OpenSUSE ended Power PC support after that release.) And plan C is to try Yellow Dog Linux, a Power PC distribution that was best known for supporting Sony's PlayStation 3 (until Sony castrated its game system by removing Linux support.) My goal is to host a website on this system, to prove that old computers can still be useful.

Part 2 of "War of the Operating Systems" will cover my quest to get Linux running on this ancient Mac, as well as exciting developments on the Linux front for Intel-based PC's. Stay tuned!