- Oct 17, 2011
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For nearly a quarter century, the International Space Station (ISS) has continuously hosted astronauts and science experiments as an enduring and beloved bastion of humanity in low-Earth orbit. Yet despite its successes, the space station’s days are numbered.
In the coming months, NASA will be evaluating commercial proposals for vehicles capable of “decommissioning” the ISS—that is, of safely dropping it into Earth’s atmosphere to burn up. The agency has said it expects to pay nearly $1 billion for this service to avoid relying on multiple Russian vehicles. The brutal ending is scheduled for early next decade but is already proving a delicate matter for aerospace engineering and international diplomacy.
Without periodic boosts, as a spacecraft in low-Earth orbit loses speed, it loses altitude as well, eventually sinking deep enough to break apart and burn up as it plunges through our planet’s atmosphere. Most of the ISS’s orbit-maintaining boosts come from a steady supply of Russian Progress cargo vehicles that, once docked with the station, periodically fire their engines to counteract the space station’s constant sinking.
[Ideally...] After weeks or months of natural orbital decay that would slowly lower the ISS’s altitude, at circa 250 miles above Earth, a custom-built vehicle attached to the space station would begin a deorbit burn. The station could then descend about halfway to the planet’s surface before encountering destabilizing effects. At around 125 miles in altitude, mission controllers would adjust the ISS’s trajectory, tweaking the rocket’s burn to reshape the station’s roughly circular orbit into an ellipse, with its closest earthward point, or perigee, perhaps 90 miles above the planet. This would help minimize the amount of time that the station would spend in lower, denser levels of the atmosphere during the remainder of its descent. From that 90-mile perigee, mission control would command the rocket to fire a final time, pushing the station even farther down to fall over the South Pacific.
In the coming months, NASA will be evaluating commercial proposals for vehicles capable of “decommissioning” the ISS—that is, of safely dropping it into Earth’s atmosphere to burn up. The agency has said it expects to pay nearly $1 billion for this service to avoid relying on multiple Russian vehicles. The brutal ending is scheduled for early next decade but is already proving a delicate matter for aerospace engineering and international diplomacy.
Without periodic boosts, as a spacecraft in low-Earth orbit loses speed, it loses altitude as well, eventually sinking deep enough to break apart and burn up as it plunges through our planet’s atmosphere. Most of the ISS’s orbit-maintaining boosts come from a steady supply of Russian Progress cargo vehicles that, once docked with the station, periodically fire their engines to counteract the space station’s constant sinking.
[Ideally...] After weeks or months of natural orbital decay that would slowly lower the ISS’s altitude, at circa 250 miles above Earth, a custom-built vehicle attached to the space station would begin a deorbit burn. The station could then descend about halfway to the planet’s surface before encountering destabilizing effects. At around 125 miles in altitude, mission controllers would adjust the ISS’s trajectory, tweaking the rocket’s burn to reshape the station’s roughly circular orbit into an ellipse, with its closest earthward point, or perigee, perhaps 90 miles above the planet. This would help minimize the amount of time that the station would spend in lower, denser levels of the atmosphere during the remainder of its descent. From that 90-mile perigee, mission control would command the rocket to fire a final time, pushing the station even farther down to fall over the South Pacific.
