Starman drives Eton Musk's red Tesla electric roadster toward Mars and beyond

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Starman drives Eton Musk's red Tesla electric roadster toward Mars and beyond

Post by jserraglio » Thu Feb 08, 2018 4:09 pm

The Atlantic
Where Is Elon Musk's Space Tesla Actually Going?
The payload of SpaceX's recently launched rocket overshot its planned orbit near Mars.

CAPE CANAVERAL, Fla.—There is, at this very moment, a shiny red car floating around in our solar system.

The car, a 2008 Tesla Roadster, hitched a ride to space on what is now the most powerful rocket in operation, the Falcon Heavy, built by Elon Musk’s company SpaceX. The goal of the Falcon Heavy’s first flight—aside from not blowing up—was to put the Tesla into an elliptical orbit between Earth and Mars, a car and two planets joined together in an endless loop around the sun. That kind of orbit would, at certain times, bring the Tesla near Mars.

The Tesla successfully reached orbit Tuesday afternoon, attached to the upper part of the rocket, and coasted for about six hours—a move meant to demonstrate a new capability for the U.S. Air Force, one of SpaceX’s customers. A livestream from the payload showed surreal views of the car and its sole passenger, a mannequin stuffed into a SpaceX space suit, floating above Earth. Then SpaceX cut the feed, and the upper stage’s engine reignited one last time to give the Tesla a final push into its destined orbit.

After that final blast, Musk shared the Tesla’s location. The car was heading to the asteroid belt.

Wait, what?

The graphic above indicates that SpaceX has calculated the payload’s orbit, and it turns out that the final engine blast propelled the Tesla farther than expected. The push, the pictured orbit seemed to suggest, caused the car to overshoot its final destination and sent it barreling toward the asteroid belt between the orbits of Mars and Jupiter, a ring of small rocks and dust. The largest object in the asteroid belt is a dwarf planet called Ceres.

Astronomers jumped into action, trying to make sense of it all and talking it out together on social media. The numbers provided, they quickly realized, didn’t exactly match up with the orbit pictured.

“We collectively assumed that the numbers on Musk’s tweet were based on telemetry, and that they’d know best,” says Andy Rivkin, a planetary astronomer at Johns Hopkins Applied Physics Laboratory who studies asteroids.

Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who has been live-tweeting his attempts to discern the correct orbit, tweeted Wednesday, “Elon is still talking about the Starman going to the asteroid belt,” referring to the nickname Musk gave the dummy driver in a nod to David Bowie. “But I’m not convinced yet ...”

Musk’s plot provides numbers for two kinds of points in the orbit of the Tesla: aphelion, the car’s farthest distance from the sun, and perihelion, its closest distance to the sun. Astronomers like Rivkin, McDowell, and others (and probably anyone else less afraid of math than I am) take the average of these two figures and use that to calculate the orbit period of the Tesla.

But because the numbers here seemed off, Rivkin says he and others turned to independent observations made by Rob McNaught, an Australian asteroid observer, which were posted online. Late Wednesday night, their suspicions were confirmed. Revised orbital data provided by SpaceX and shared with nasa’s Jet Propulsion Laboratory’s system for tracking solar-system bodies showed the original graphic was incorrect.

So, based on the corrected numbers, the car actually won’t make it as far as the asteroid belt, as Musk claimed in his tweet.

According to the revised data, Rivkin says, it will take the Tesla about 18.8 months to complete one trip around the sun. This means that the car will reach its farthest distance from Earth in about half that time. The Tesla will cross the orbit of Mars twice per orbit, so Musk is still fulfilling his wish to send his Tesla “to” Mars—it’ll just take a little longer between visits.

The new numbers suggest the payload reached a speed of 33.5 kilometers per second after the last push, which Rivkin says is about 2.5 percent more speed than SpaceX would have needed to keep the Tesla from going no farther than the orbit of Mars.

“I have no idea whether that’s because they wanted some margin, or things were more efficient than they were expecting, or what,” Rivkin says. “If this were a real Mars mission, this would be a disastrously wrong orbit and might not be recoverable. But since this may have been ‘put it up to full throttle and let’s see what this baby can do,’ it’s not a problem.”

Musk’s tweet sounds like the Tesla is approaching the asteroid belt, but it’s not. “Musk’s message is a bit ambiguous,” Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy, said in an email. “The payload is still very much near the Earth.”

Weryk has some experience in tracking unusual-looking objects in the solar system. He was the first to lay eyes on ‘Oumuamua, the first known interstellar object to visit our solar system, while looking through the data of the Pan-starrs telescope in Hawaii last October. ‘Oumuamua was traveling much faster than the Tesla, and it's probably only now reaching the asteroid belt.

If the Tesla did reach the asteroid belt, the car would stick out like a sore thumb in terms of appearance, but not necessarily in size. “Depending on if you take the size of the car or the size of the car plus second stage (that it’s apparently attached to), there are billions to trillions of objects of that size already in the asteroid belt,” Rivkin says.

The car may have even found itself on a collision course with its new neighbors—but nothing too bad. “The asteroid belt is quite large, and they are spaced much farther apart than you might think,” Weryk said.

Instead, the Tesla would have been bombarded by teeny, tiny cosmic dust. “It'll probably get hit with something the size of very fine sand every year or so, and get hit a few times an hour with 100-nanometer-size dust,” Rivkin says. “On average, we think it’d get hit by a fist-sized rock every several million years.”

Whatever the Tesla’s exact orbit is now, it won’t stay the same forever. Out there in the solar system, the car will be subject to the gravitational tugs of other planets.

Before the Falcon Heavy launched, Musk told reporters the Tesla would at times come “extremely close” to Mars. “There’s a tiny chance that it will hit Mars,” he said. “Extremely tiny.”

If the Tesla avoids a collision with Mars—and anything else—it will remain in its loop around the sun for perhaps hundreds of millions of years. Powerful telescopes like Pan-starrs may be able to see the Tesla if it crosses their field of view—and if it’s not too cloudy—“at least for a time until it is too faint,” Weryk said. If they don’t see it now, they can try again in 11 years, when the Tesla should approach the Earth, according to corrected data. Astronomers track near-Earth objects like asteroids and comets by looking for the sunlight reflected by their surfaces. A shiny red car is much brighter than a plain old rock.

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