Is it possible to reach the space station via trampoline?
In response to US sanctions aimed at Russia's space industry, Russian Deputy Prime Minister Dmitry Rogozin suggested that US astronauts get to the space station using a trampoline. Given a big enough trampoline, could that actually work?
Responding to new US sanctions to be imposed against his country in response to the Ukraine crisis, Russian Deputy Prime Minister Dmitry Rogozin took to Twitter on Tuesday to propose a novel way for US astronauts to travel to the International Space Station.
"After analyzing the sanctions against our space industry," Dr. Rogozin tweeted in Russian, "I suggest to the USA to bring their astronauts to the International Space Station using a trampoline."
Following the conclusion of the Space Shuttle program in 2011, Russia's space program is the world's only institution currently capable of manned spaceflight. When US astronauts visit the International Space Station, they travel via Russian Soyuz spacecraft, at a fare of about $70 million per seat. Given the heightened tensions between our two countries, it's not unreasonable for the US to at least consider alternative transportation.
So exactly how feasible is Rogozin's suggestion? Could a trampoline furnish an astronaut with the one giant leap needed to reach the space station, which orbits 220 miles above the Earth's surface?
Doing so would require significant trampolining advances, but Americans are nothing if not innovative. Just three weeks ago, in New York City's Rockefeller Plaza, acrobat Sean Kennedy, propelled by the combined kinetic energy of his brothers Eric and T.J., set the Guinness World Record for the highest trampoline jump, at 22 feet 1 inch, or 0.0018 percent of the distance to the space station.
Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics calculates that, for a trampolining astronaut to be properly flung into space, we would need a hole about one kilometer deep for the trampoline to stretch into. But he cautions that ordinary trampoline fabric would not be up to the task. "That's a problem for material scientists," he says.
Even if NASA were to design and build such a trampoline, say, by stretching some exotic, super-stretchy material across the Grand Canyon, an astronaut still wouldn't be able to bounce into space.
"Unlike a rocket, which uses stored chemical energy to propel you into space, a trampoline doesn't actually give you any energy," says Dr. McDowell, citing the First and Second Laws of Thermodynamics, which, among other things, preclude the existence of perpetual-motion substances such as Flubber.
Trampolinists are able to bounce ever higher by crouching as they land and then pumping their legs (which are powered by chemical energy in the form of lunch). Unlike, say, a hardwood floor, a trampoline converts most of trampolinist's kinetic energy into potential energy, which then gets converted back into kinetic energy as the fabric and springs rebound to their previous shapes.
"But it's not perfect," says McDowell of the conversion. "You don't get 100 percent of the energy back." Eventually, the inefficiencies in the trampoline, combined with atmospheric drag, will prevent the trampolinist from bounding any higher.
So instead of having our astronaut jump up and down, the next logical step would be winch the fabric one kilometer downward, perhaps by enlisting those Grand Canyon mules. We could then place the astronaut on the trampoline and catapult him into space.
That might actually work, but it wouldn't be at all pleasant for the astronaut. "All the energy gets imparted at the beginning," says McDowell.
"That's really bad," he explains, "because the acceleration would squash you like a bug."
This was essentially the spaceflight method proposed by science fiction writer Jules Verne in his 1865 novel "From the Earth to the Moon." In that story, members of a gun club construct a huge cannon to fire a manned projectile to the lunar surface.
In 1903, pioneering rocket scientist Konstantin Tsiolkovsky calculated that Verne's space gun would subject its passengers to an acceleration 22,000 times the force of gravity. (To get a sense of what that would feel like, have 22,000 people stack themselves on top of you.)
What's more, getting yourself 220 miles above the Earth's surface isn't the hard part of space travel. Even at that altitude, the force of gravity is about 90 percent of what it is on the Earth's surface, so you'd just fall right back down.
The real trick is to move sideways fast enough so that, when you do fall down, the curvature of the Earth's surface will be such that it guarantees that you don't hit the ground. This is what's known as "being in orbit," and it takes about 30 times as much energy to reach orbital speed as it does to simply reach the edge of space.
"If you just jump up to the space station," says McDowell, "you'll become a nasty splat on its windscreen, because it's traveling 18,000 miles per hour and you're not."
The one non-rocket method of reaching space that has gotten the most serious attention is what's known as a space elevator. First conceived of by Tsiolkovsky in 1895, it consists of a 46,000-mile-long tether anchored to the Earth's surface. At the other end its a counterweight, and its center lies at geostationary orbit, at a fixed point in the sky from the perspective of someone on the ground looking up at it.
The tether would have to be made of a material stronger than diamond. Researchers speculate that another form of carbon – cylindrical molecules called carbon nanotubes – might do the trick. "That's a really cheap and easy way to get into space once you've spend the trillions of dollars building the thing," says McDowell.
Nonetheless, McDowell, who since 1989 has published the twice-monthly Jonathan's Space Report, which details all space launches, manned and unmanned, is skeptical that we'll ever build a space elevator, thanks in part to the planet-wide catastrophe that could occur if the tether snaps. "I really don't think you want a structure that size falling down," he says. "The failure scenarios are too scary."
So, at least in the short term, if we want to leave Earth, we'll have to content ourselves with being propelled by controlled explosions that hurl matter at high speeds in the opposite direction of wherever we want to go.
"I think until we come up with some new physics," McDowell says, "something that's basically a rocket is the only way to do this."