Trouble on Private Space

>> SpaceShipOne was the Burt Rutan-designed plane which flew 100 km into space and won the X prize in 2004; it's being developed commercially by Virgin. It's no great surprise that news of this explosion didn't get much publicity. This plane's hybrid rocket really *shouldn't* explode, it's just rubber and nitrous oxide, but whaddya know?

July 27, 2007

Mojave Spaceport
Image: Californiacondor

Three people were killed and another three seriously injured in a blast at Mojave Spaceport, located in California, United States. The blast occurred on Thursday at 2:34 p.m. PDT (UTC-7) while Scaled Composites was conducting cold flow test of a rocket engine.

According to Tony Diffenbaugh of the Kern County Fire Department, two of the victims died immediately in the blast, while the third succumbed to his injuries at the hospital.

"Our units arrived on the scene at a remote test site in the northeast portion of the airport. What they found was six victims of an apparent explosion with various traumatic and burn injuries," Diffenbaugh said.

Burt Rutan, founder of Scaled Composites, said a press conference: "We just don't know" why the explosion occurred, nitrous oxide usually is "not considered a hazardous material."

Scaled Composites is in a partnership with Richard Branson's Virgin Galactic to build SpaceShipTwo, which hopes to become the first commercially available passenger spaceflight for space tourism.

The accident comes just days after Northrop Grumman announced it would increase its stake in Scaled Composites to 100%.

>> Elon Musks's SpaceX project aims to put objects in orbit with more standard liquid oxygen rockets, much more difficult than the 100 sub-orbit that defines 'space'. Unfortunately its second flight failed to reach orbit because of control issues:

Second test flight of Falcon 1

The second Falcon 1 launched a demonstration payload to return data on the booster's performance, however it failed to reach orbit. The second stage was shut down about a minute and a half before schedule (T+ 7:30) due to a control issue. ^[4] SpaceX later stated that "The second stage was otherwise functioning well and even deployed the satellite mass simulator ring at the end of flight! Actual final velocity was 5.1 km/s or 11,000 mph, whereas 7.5 km/s or 17,000 mph is needed for orbit."

The first launch attempt was targeted for 2300 UTC, 20 March 2007 however it was aborted one minute and two seconds prior to launch (T minus 00:01:02) due to a ground control software handover failure. A second attempt was made at 00:05 UTC, 21 March 2007, but the launch was aborted automatically 0.5 seconds after firing the engines because the main engine chamber pressure was about 0.2 percent lower than allowable. The low pressure was caused by the fuel being colder than desired. The third attempt successfully launched the rocket at 01:10 UTC, 21 March 2007 (13:10 local time, 20 March 2007), the vehicle separated from the first stage booster and fairing at approximately 6:14 PST.

The webcast from the vehicle was lost at T+ 5:05 at an altitude of approximately 300 kilometers, but SpaceX was able to retrieve telemetry for the entire mission. The video showed a coning motion that increased during the second stage burn, then a roll immediately before loss of signal.^[5] Musk noted that the control problem was initiated during stage separation, when the shut down kick of the main engine exceeded their predictions. This caused a bump between the first stage and second stage engine nozzle, along with sloshing in the tanks. The vehicle's systems were designed to damp out sloshing, but the unexpected motion exceeded design parameters. ^[4]

SpaceX stated they were happy with the launch as the rocket reached space and validated the riskiest and most difficult parts of the new design. Musk expressed confidence that they would solve the control issue and noted that all new rockets typically have these problems to work out; "I think they had something like 12 Atlas failures before the 13th one was success. To get this far on our second launch being an all-new rocket -- new main engine, new first stage, new second stage engine, new second stage, new fairing, new launch pad system, with so many new things -- to have gotten this far is great." ^[6] A post-mission report declared this launch "the end of the test phase for Falcon 1 and the beginning of the operational phase." ^[7]

>>> Finally, it appears that early estimates that carbon nanotubes (a form of carbon stronger than diamond) are a candidate material for building a skyhook (see here) were overly optimistic. First, because the measured tensile strength of real nanotubes are about half of their theoretical limit; and second, because the impurities which cause this weakness are more or less inevitable.

arXiv:cond-mat/0601668

In this paper various deterministic and statistical models, based on new quantized theories proposed by the author, are presented for estimating the strength of a real, and thus defective, space elevator cable. The cable, ~100 000 km in length, is composed of carbon nanotubes, ~100 nm long: thus, its design involves nanomechanics and megamechanics. The predicted strengths are extensively compared with the experimental and atomistic simulation results for carbon nanotubes available in the literature. All these approaches unequivocally suggest that the megacable strength will be reduced by a factor at least of ~70% with respect to the theoretical nanotube strength, today (erroneously) assumed in the cable design. The reason is the unavoidable presence of defects in so huge a cable. Preliminary in-silicon tensile experiments confirm the same finding. The deduced strength reduction is sufficient to place in doubt the effective realization of the space elevator, that if built as designed today will certainly break (in the author's opinion). The mechanics of the cable is also revised and possible damage sources discussed.

>> For all that, the mass production of long nanotubes has grown by leaps and bounds and now exceeds the length extimated here by a factor of several million:

The carbon nanotubes grew atop a specially designed wafer catalyst that allowed growth to continue for a relatively long duration. The individual fibers are difficult to discern in this image but appear as striations when they catch the light.

>>> Seems as though characterizing strength (single tube or weave) would now be vastly easier with these 2 cm long tubes but I've not been able to find a study. The best estimates of strength continue (?) to be over seven years old.

Green House
Flipping properties with a nod to Mother Earth at Second Nature Homes

By Jennifer Garrett

When Darin Harris and Dawn McCluskey spot a ramshackle ranch in a nice neighborhood, they immediately start to see green. But this remodeling duo has more than dollar signs in their eyes. This pair of tree huggers has launched a business so that they can turn a profit while treading lightly on the environment.

Like hordes of other part-time real estate investors, this husband-wife team has bought and rehabbed several houses, usually while living in them as they fixed them up. Each time they made a profit, even when they used contractors for much of the work. More importantly to them, though, is that they made money even when they bypassed standard materials and processes in favor of eco-friendly choices.

That got them thinking. They could use real estate to generate income without clouding their collective conscience. So Harris, a consultant at UW--Madison, and McCluskey, a veterinarian, concocted Second Nature Homes. They would buy rough-around-the-edges houses in neighborhoods with good appreciation potential, renovate the homes and then sell them for a profit -- all without living in a construction site, without giving up their day jobs and without compromising their environmental principles.

"We're sort of green flippers," Harris says, referring to the real estate term for buying, fixing up and selling houses relatively quickly. "We're not doing this just for the money. Your home uses more resources than any other part of your life … so we're out to save resources, including energy, and improve health."

Right now they are rehabbing a three-bedroom ranch in Nakoma. They've replaced the furnace, gutted the bathroom, exposed part of the basement so they could turn it into an additional bedroom, and otherwise upgraded and updated everything. All the while they use low-emission paints, formaldehyde-free insulation and Energy-Star-certified appliances and materials.

Harris says all of Second Nature Homes' projects will meet or exceed requirements for Wisconsin Green Built Home certification, a voluntary program that sets standards for sustainable building practices and energy efficiency.

While Green Built Home has had guidelines for new home construction since 1999, the organization implemented its remodeling program just last year. Nathan Engstrom, program director for Green Built Home, says Second Nature Homes is not only the first Wisconsin company enrolled in the program, but it is also the only remodeling business expressly founded on the principles of green building. "It wasn't an afterthought or an add-on," Engstrom says. "From the very beginning, from the ground up, they have built their business on these concepts."

Harris and McCluskey know that green isn't the only way to go, but they think it's the best one. And they think other homeowners and investors would agree if they knew more about it and had some proof that environmentally friendly renovations could also make money. "We hope to set a standard," Harris says. "We're going to spend a little more money remodeling this house than they average remodeler would, but we will sell it at market rate. It sounds a little too good to be true, but we did a really good job negotiating the price on the front-end."

For the time being, Second Nature Homes will continue as a part-time venture, but McCluskey and Harris plan to keep at it as long as they continue earning a solid return on their investment. "I really like my work, so there are no plans to take this full time," Harris says. "We'll just take it one house at a time and see how it goes."