Chris Eaton

Fruit fly

Wikimedia Commons

How does the brain tell the body to walk backward? Scientists don't know. To find out, researchers developed 3,500 different strains of fruit flies. Each genetically-modified fly carried genetic switches in different parts of the brain that are activated by heat, a technique called thermogenetics. When these genetic switches were activated, they caused different neurons to fire. The scientists finally found a fly that began walking backward when its genetic switches were activated by heat, and from there they found which neurons were firing. 

As it turns out, walking backward (at least in fruit flies) is controlled by two neurons. As Science Magazine explains: 

The first neuron appears to be the "initiator," compelling the fly to "moonwalk" when it encounters certain cues, like an obstacle. And the second gene acts like a brake, perhaps preventing it from backing into something. The researchers, whose study was published in Science, will use these neurons as a starting point to find other networks involved in walking backward, such as those responsible for touch, sight, and smell.

[Science]

BAE Railgun

Naval Sea Systems Command

In 2016, the U.S. Navy is going to test a railgun—a weapon that can repeatedly launch a projectile at more than 5,000 MPH—from a boat. In 2018, they're going to do it again. And in the 2020s, the Navy is going to figure out just what to do with a gun that seemed like science fiction decades ago.

Speaking at the Navy League's Sea Air Space exposition in National Harbor, Maryland, Rear Admiral Bryant Fuller told the assembled crowd of journalists, servicemen, and defense contractors that railgun shots cost 1/100th the price of a “standard” missile. (In the age of austerity, even something as futuristic as a railgun is sold on the premise of cost savings.)

A railgun works by generating a strong electromagnetic current that flows from one rail, through a U-shaped back end of the projectile, and into another parallel rail. This generates three magnetic fields—a parallel one around each of the rails, and a perpendicular one around the projectile. Squeezed forward by the magnetic fields, the projectile accelerates rapidly along the rails and is then launched forward, breaking the circuit. The end result is a large metal slug that can go very far, very fast.

Here's a video explaining the physics:

Scientist figured out the physics behind rail guns a while ago, and have tested them on land, but the main constraint on making a practical one is generating enough electrical power.

That's understandable. A railgun system needs 25 megawatts of energy flowing through it, and according to Captain Michael Ziv, the Navy's program manager for rail guns and energy weapons. Most currently serving destroyers don't have more than nine megawatts of electricity that they can shift around. 

Future ships like the Zumwalt class of destroyers with "integrated power systems" that make it really easy to assign electrical power can get around this. The Navy is keeping open the option of outfitting current ships with railguns, as they can bring batteries storing the extra power needed on board. The Navy is going to test the railgun at sea in 2016 from the back of the USNS Millinocket, a transport and supply ship. 

How far the shot goes depends on the power supplied. Smaller railguns might release a projectile at 20 megajoules, which means that at flying level it can go up to 60 miles. A larger railgun, the kind that draws 25 megawatts of power, can release projectiles at 32 megajoules of energy, where they will travel up to a 110 miles at a level trajectory. With the 25 megawatts, a railgun can also fire up to 10 times a minute, creating an anti-ship or anti-coastal weapon that's fast firing, cheaper than a missile, and at least as deadly.

If the tests go well, it's not just the Navy that's interested. The U.S. Army is working with the Navy to develop the railguns, meaning the weapon could one day attack both from the sea and the land.

Here, by the way, is what one of these looks like firing from land:

Making biofuel

Georgia Tech researchers examine the production of the hydrocarbon pinene in a series of laboratory test tubes. Shown are (l-r) Pamela Peralta-Yahya, an assistant professor in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering, and Stephen Sarria, a graduate student in the School of Chemistry and Biochemistry.

Georgia Tech Photo: Rob Felt

In an effort to launch things skyward in a more sustainable way, researchers have coaxed bacteria to produce a highly combustible compound called pinene. Conifers naturally excrete the stuff in their resin, lending the plants part of their distinctive scent. Pinene also happens to rival the properties of JP-10--a liquid rocket fuel that's widely used for commercial and military launches.

So, pretty soon a rocket or missile flying overhead might spew exhaust that smells like pine trees.

JP-10 and other energy-dense rocket fuels are derived from oil and don't come cheap. (The cost of JP-10 is about $25 per gallon and rising as oil demand grows.) Meanwhile, no biofuels today can compete with traditional rocket fuels on the market. Although ethanol derived from corn, for example, can more or less replace gasoline, even the latter and more energetic fuel packs about 20 percent less punch per gallon than JP-10.

A breakthrough in rocket-compatible biofuel came in 2011. That's when the Navy discovered chemicals that link together, or dimerize, two molecules of pinene into a fuel with properties similar to JP-10. Because leveling pine forests to extract a little pinene isn't practical, however, researchers have since sought alternative production methods.

The new research effort--a joint venture by Georgia Tech and the Department of Energy--builds on the work of the Navy by offloading pinene synthesis to bacteria. The group genetically engineered E. coli bacteria to produce conifer-derived proteins that assemble pinene.

Stephen Sarria and Pamela Peralta-Yahya, two Georgia Tech researchers who collaborated on the new work published in ACS Synthetic Biology, broke down the process for Popular Science in four steps: 

First, the researchers picked two groups of enzymes--pinene synthases and geranyl diphosphate synthases--to produce molecules of pinene. Second, they inserted genes that code for the enzymes into the DNA of E. coli (chosen because it's one of the easiest bacteria to genetically engineer). Third, the team grew up the bacteria in large fermenters, “very similar to how you'd make beer,” Peralta-Yahya said. With the brewing of pinene complete, they used the Navy-discovered chemicals to dimerize pinene molecules into rocket-ready fuel.

This new bacteria-driven method to make pinene is six times better than any other biological process, but the yield is still quite low. “Right now we’re seeing about 1 percent of theoretical yield," Peralta-Yahya said. "To be commercially competitive, we need to reach about 26 percent of theoretical yield."

The biggest hurdle for the team right now is pinene synthase itself. Both the enzyme's product, pinene, and its partner enzymes, the geranyl diphosphate syntheses, inhibit pinene-creating activity. Peralta-Yahya says there are two ways to solve the problem: either engineer a new kind of pinene synthase, or lower the concentration of geranyl diphosphate synthase.

For now, the team is trying both methods in hopes of making a “drop-in” biofuel that's cheaper and more sustainable option for launching rockets or missiles without changing engines or existing infrastructure.