Category Archives: Science/Medicine

Thrust from Nothing

Really. It’s the controversial Em Drive, and it’s NASA science and peer-reviewed and everything. Formally it’s called “Measurement of Impulsive Thrust in a Closed Radio Frequency Cavity in Vacuum” by Harold White, Paul March, James Lawrence, Jerry Vera, Andre Sylvester, Davis Brady and Paul Bailey.

As Engaget explains it,

An EM Drive produces thrust without fuel, instead using microwaves that bounce around a conical, enclosed device. According to the theory, the momentum of those bouncing microwaves is higher at the wide end of the engine, which means the whole system should experience thrust.

I don’t pretend to understand the pilot-wave theory that the authors of the new paper propose as an explanation, but I gather it challenges the Copenhagen consensus that has dominated physics for a long time — and makes quantum behavior a tiny bit less weird in some ways (double slit experiments would have an explanation I could understand) but at a price of making large pieces of the universe more likely to be connected in some odd way. Or something.

But this part I think I get:

Although this test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust-to-power figure of 1.2mN/kW in context. The current state-of–the-art thrust to power for a Hall thruster is on the order of 60mN/kW. This is an order of magnitude higher than the test article evaluated during the course of this vacuum campaign; however, for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2mN/kW performance parameter is over two orders of magnitude higher than other forms of “zero-propellant” propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33–6.67μN/kW (or 0.0033–0.0067mN/kW) range.

Yes, “for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements”.

Space! As long as you are not in a hurry to boost up to speed to get there.

I wonder if the Em Drive works equally well at relativistic velocities? Does thrust taper off if you are going faster relative to the pilot wave? (Does that question even make sense?)

UPDATE: Well, of course, it’s the Internet, so there’s an emdrive FAQ. And it seems you do lose thrust as you go faster:

Q. Why does the thrust decrease as the spacecraft velocity along the thrust vector increases?
A. As the spacecraft accelerates along the thrust vector, energy is lost by the engine and gained as additional kinetic energy by the spacecraft. This energy can be defined as the thrust multiplied by the distance through which the thrust acts. For a given acceleration period, the higher the mean velocity, the longer the distance travelled, hence the higher the energy lost by the engine.
This loss of stored energy from the resonant cavity leads to a reduction in Q and hence a reduction of thrust.

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Soother

Allegedly, listening to this song “was clinically proven to reduce stress levels up to 65% in the people who listened to it.” Here’s the official video verion:

Personally I’d prefer something with a hammock (and no mosquitoes):

soothing-hd-wallpaper

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Drat

Slashdot has an excited item about a new catalyst that turns CO2 dissolved in water into ethanol. CO2 To Ethanol In One Step With Cheap Catalyst Sounds great, right?

Not so fast: if I understand it (corrections welcomed!) the paper itself warns it still takes too much energy to be worthwhile:

We report an electrocatalyst which operates at room temperature and in water for the electroreduction of dissolved CO2 with high selectivity for ethanol. The overpotential (which might be lowered with the proper electrolyte, and by separating the hydrogen production to another catalyst) probably precludes economic viability for this catalyst, but the high selectivity for a 12-electron reaction suggests that nanostructured surfaces with multiple reactive sites in close proximity can yield novel reaction mechanisms. This suggests that the synergistic effect from interactions between Cu and CNS presents a novel strategy for designing highly selective electrocatalysts.

Guess we haven’t solved global warming yet.

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Seems Like a Big Deal

Quantum entanglement achieved at room temperature in semiconductor wafers – phys.org.

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Y2K Watershed for Medical Studies

Scary news via Slashdot:

The requirement that medical researchers register in detail the methods they intend to use in their clinical trials, both to record their data as well as document their outcomes, caused a significant drop in trials producing positive results. From Nature: “The study found that in a sample of 55 large trials testing heart-disease treatments, 57% of those published before 2000 reported positive effects from the treatments. But that figure plunged to just 8% in studies that were conducted after 2000. Study author Veronica Irvin, a health scientist at Oregon State University in Corvallis, says this suggests that registering clinical studies is leading to more rigorous research. Writing on his NeuroLogica Blog, neurologist Steven Novella of Yale University in New Haven, Connecticut, called the study “encouraging” but also “a bit frightening” because it casts doubt on previous positive results.”

In other words, before they were required to document their methods, research into new drugs or treatments would prove the success of those drugs or treatment more than half the time. Once they had to document their research methods, however, the drugs or treatments being tested almost never worked.

According to the Nature article, the reason is this:

… by having to state their methods and measurements before starting their trial, researchers cannot then cherry-pick data to find an effect once the study is over. “It’s more difficult for investigators to selectively report some outcomes and exclude others,” …

But is anyone going back to review the last 40 years of studies with positive results? I doubt it.

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Pluto and Charon

nh-071315_falsecolorcomposite-1024x576

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