Tag Archives: spaceflight

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When testing gravity, no news is good news

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Looking for nothing to test gravity

When they look for violations of Einstein’s general relativity, physicists deliberately plan experiments to find nothing at all.

For Symmetry Magazine:

In 1887, physicists Albert Michelson and Edward Morley performed one of physics’ most famous experiments (at Case Western Reserve University, coincidentally, across the street from where this article was written). Unlike other important experiments, they didn’t find what they were looking for, but unexpectedly their “null” result prepared the way for the theory of relativity.

Sometimes researchers deliberately set out to generate null results—while on the lookout for something new. One type of experiment is looking for deviations from Einstein’s general theory of relativity.

“General relativity has been the staple of gravitational understanding for 100 years,” says Katie Chamberlain, a physics student at Montana State University. “We have to rule out the potential for other existing theories to come in and replace [it].”

[Read the rest at Symmetry Magazine…]

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In a certain sense, it’s easy to keep things in orbit around Earth. However, it’s hard to keep satellites in a specific orbit, which is what matters most for communicating with them and they with us, whatever task they’re designed to perform. Thanks to the work of rocket engineer Yvonne Brill in the early 1970s, the process is remarkably automatic.

Brill’s design eliminated this redundancy and lightened the spacecraft in the process. She also used a type of fuel called hydrazine, which is so reactive you don’t need oxygen or another chemical injection to ignite it. (On Earth, we’ve got lots of oxygen available for making things burn, but in space, you need to carry your own fuel for fire.) Brill’s system pumped liquid hydrazine through an aluminum nozzle. The chemical composition of the nozzle reacted with it, splitting it into smaller molecules and releasing a lot of energy. [Read more…]

I’m no rocket scientist, but I can appreciate the challenges of engineering something that needs to stay in the same orbit for years or decades. Yet the New York Times obituary for Brill mentioned her remarkable achievements as a sort of afterthought, as though they weren’t very important, really, in the scheme of things. My piece isn’t an obituary—I mostly write explanatory pieces about science, after all—but Brill’s contribution to spaceflight in general and the communications satellite revolution of the 1980s is astounding.

Yvonne Brill and the technology keeping satellites in orbit

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Yesterday, Austrian skydiver Felix Baumgartner (best known for jumping off skyscrapers) successfully completed a 39 kilometer dive from a balloon. Many media outlets described his jump as beginning “at the edge of space”, but the story is a little more complex than that.

One thing bothered me, though, about a lot of the coverage: many people said Baumgartner was jumping “from space” or “from the edge of space”. Don’t get me wrong—39 km is a long way up, about 4 times the altitude of commercial airliners, so I’m not denigrating this accomplishment at all. Atmospheric pressure is about 2% of its value at Earth’s surface at 39 km, and the temperatures are pretty cold, so Baumgartner had to wear a pressurized suit and carry an air supply. (If memory serves, the temperature was -7° C or 19° F when the dive began.) However, it’s not what is conventionally considered “space”: it’s within the region of Earth’s atmosphere known as the stratosphere (which also explains the project’s official name, “Stratos Jump”). So, if Baumgartner didn’t jump from space, where is the boundary of space? [Read more….]

Jumping from the “edge of space”…whatever that means