NASA has unveiled an ambitious $1 billion plan to retire the International Space Station (ISS) and guide it back to Earth. This decision stems from the accumulating structural stresses on the ISS, leading the space agency to decommission the orbiting laboratory in 2031.
In pursuit of this endeavor, NASA has initiated a call for designs of a ‘space-tug’ capable of handling the monumental task of redirecting the ISS from its current orbit. This craft, referred to as the US Deorbit Vehicle (USDV) by NASA, will play a pivotal role in gently guiding the ISS from its position approximately 175 miles above the Earth’s surface to a lower altitude of around 75 miles. At this point, the ISS will embark on its final descent, eventually splashing down in the Pacific Ocean.
To participate in this venture, proposals for the USDV design must be submitted no later than November 17. The ISS retirement plan is scheduled to commence in 2026, at which point NASA will allow the station to gradually descend on its own.
Renowned astrophysicist Jonathan McDowell, from Harvard University, commented on the initiative, stating, “This has been done before, notably with the Mir space station. Many tons of material will hit the ocean relatively intact, and there will definitely be a warning to clear the airspace (we get about one of these a month for disposal of much smaller spacecraft like ISS cargo ships.) Here’s what’s tricky. You can fly the ISS safely down to an altitude of about 250 km. After that, you need this special USDV ship to take over the steering – it’s like driving down a motorway with a lot of wind gusts – you need a lot of muscle power to stay on the road. If you ever lose control and the ISS starts tumbling, you’re in trouble because then you can’t reliably point the rocket engines in a particular direction.”
NASA’s comprehensive plan commences by allowing the International Space Station (ISS) to gradually decay without re-boosting it to maintain its orbit. During this phase, the ISS will experience a natural reduction in orbit altitude, transitioning from its current position approximately 250 miles above Earth’s surface to an altitude of about 200 miles. This process, however, will unfold over several years.
As we approach the year 2030, the ISS crew will embark on the final descent to Earth, taking with them any essential equipment. The ISS will continue its descent, drawing nearer to the critical “Point of no return” at approximately 175 miles above Earth’s surface. It is at this juncture that the pivotal $1 billion space tug, the USDV, will come into play, giving the ISS a gentle nudge to facilitate its orbital descent.
The ISS will begin its re-entry into Earth’s atmosphere at an altitude ranging from 75 miles to 50 miles above the surface. During this phase, the outer layers of the station’s modules will succumb to the intense heat and melt away. Subsequently, the exposed hardware will vaporize as the ISS hurtles through the atmosphere at a speed of 18,000 miles per hour. Any remnants that survive re-entry will be strategically targeted to land in Point Nemo, a region in the Pacific Ocean situated between New Zealand and South America. Point Nemo is frequently utilized as a spacecraft graveyard and has witnessed the final resting place of no less than 260 spacefaring vessels.
Explaining the technical intricacies of this mission, astrophysicist Jonathan McDowell highlights the need for approximately 8 tons of propellant (fuel and oxidizer) to bring the ISS down from its lowest controllable altitude. However, using a rocket engine that consumes this amount of fuel in a leisurely six-hour burn would be impractical. Such an approach would cause the ISS to descend too rapidly, resulting in a loss of control and potential tumbling. Hence, the USDV requires a robust rocket engine capable of expending eight tons of propellant within a condensed time frame of around 15 minutes. This rapid deorbit burn ensures control is maintained throughout the descent. None of the existing cargo ships possess the requisite capabilities, necessitating the development of a new vehicle specifically tailored to safely dispose of the ISS.
The origins of the ISS trace back to President Ronald Reagan’s announcement during his State of the Union Address on January 25, 1984, when he declared NASA’s intention to complete its construction within a decade. Subsequently, on December 4, 1998, the first US component of the station was launched into space. Two years later, the ISS officially commenced its operational phase, welcoming more than 250 visitors from 20 countries since the arrival of its inaugural crew in November 2000.
NASA’s original plan to retire the International Space Station (ISS) after 15 years of operation has long since passed. However, the aging space laboratory is now showing signs of wear and tear, necessitating NASA’s decision to bid farewell to this stalwart vessel of scientific exploration.
The responsibility for the safe deorbit of the ISS is a collective effort involving five major space agencies: NASA, CSA (Canadian Space Agency), ESA (European Space Agency), JAXA (Japan Aerospace Exploration Agency), and the State Space Corporation Roscosmos. Each agency is tasked with the management and control of the hardware it has contributed to the ISS. The station was deliberately designed to function interdependently, relying on contributions from across this international partnership. Commitments to operate the ISS extend through 2030 for the United States, Japan, Canada, and ESA participating countries, and at least until 2028 for Russia.
NASA conducted a thorough examination of various options for decommissioning the ISS. These alternatives included disassembling and returning the components to Earth, boosting the station to a higher orbit to prolong its stay in space, or simply allowing it to decay in orbit until it inevitably re-enters Earth’s atmosphere at random. Regrettably, none of these options proved feasible. The ISS’s complex structure was not designed for in-orbit disassembly, re-boosting it required substantial resources, and allowing it to decay in orbit posed potential risks to Earth.
NASA’s vision extends beyond the ISS’s retirement, as the agency is determined to maintain a significant presence in space. To this end, they have initiated a transition plan, inviting private companies to develop their own space stations. Several companies, including Axiom Space, Jeff Bezos’ Blue Origin, and Northrup Grumman, have expressed interest in operating commercial stations. This forward-looking approach aims to ensure that the benefits derived from space exploration and research continue beyond the ISS era.
Robyn Gatens, the director of the International Space Station at NASA Headquarters, emphasized the station’s enduring significance, stating, “The International Space Station is entering its third and most productive decade as a groundbreaking scientific platform in microgravity. This third decade is one of the results, building on our successful global partnership to verify exploration and human research technologies to support deep space exploration, continue to return medical and environmental benefits to humanity, and lay the groundwork for a commercial future in low-Earth orbit.”
Bids for ISS demolition rights are now open, NASA declares – The Register
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