NASA’s Updated Plan To Deorbit The International Space Station
The International Space Station has been orbiting Earth for decades now. In that time it has provided some incredible science and discoveries, along with innovations and much more. However, the laboratory continues to age and cost billions of dollars each year. For these reasons among others, NASA decided the station was nearing the end of its life and would be decommissioned in the coming years.
After discussion and extensions, currently, the retirement date is scheduled to happen in 2031. However, just days ago we learned more about how the agency plans to do this and what it’s going to cost them. Specifically, when the White House released its 2024 federal budget request, NASA’s $27.2 billion allocation included $180 million “to initiate development of a new space tug” that could safely deorbit the ISS over the open ocean after its operational life ends.
This system is quite important as they need to be accurate to ensure the safety of humans with such a large structure re-entering the atmosphere. Here I will go more in-depth into the new space tug NASA is working on, the overall ISS transition plan, what to expect in the coming years, and more.
New Space Tug
Just yesterday on the 13th, NASA released additional details about its fiscal year 2024 budget proposal. With this came a 7.1% increase in the budget from 2023. However, one of the biggest new initiatives in the budget is the ISS deorbit tug, which would be used to perform the final lowering of the station’s orbit to ensure it reenters over the South Pacific. Large tugs that dock with satellites in orbit may be able to perform services like refueling or repairs or enhancements as well as changing the satellite’s orbit whether that is to extend the life of the satellite or to deorbit it.
The $180 million NASA is requesting for the tug “gives us a healthy start” for the project, said Kathy Lueders, NASA associate administrator for space operations, in a media teleconference about the budget. In reality, the budget documents didn’t include a full spending profile for the project, however, Lueders said the agency came up with a cost estimate “a little bit short of about $1 billion.” She also commented, “Our goal is to go out with an RFP [request for proposals], and then, obviously, when we get the proposals, then we’re hoping to get a better price than that. But this gives us a healthy start in ’24 to get that critical capability onboard.”
The current plan for bringing the station down safely relies upon engine burns by robotic Progress cargo vehicles, which are provided by Russia. “But we’re also developing this U.S. capability as a way to have redundancy and be able to better aid the targeting of the vehicle and the safe return of the vehicle, especially as we’re adding more modules,” Lueders said. “As you’ve seen in the past and over this last year, us having these redundancies has been very, very important for both ourselves and our partners,” she added. “And so, having a U.S. deorbit vehicle is another key linchpin in our space operations and deorbit strategy of the ISS.”
This factor becomes even more important with some of the recent issues the Russian spacecraft have experienced. For example, the Soyuz crew spacecraft lost all of its coolant to space on Dec. 14, 2022, and a Progress sprang a leak of its own on Feb. 11. Even though Russia has attributed the Soyuz leak to a likely micrometeoroid strike and linked the Progress issue to an “external influence” perhaps a problem incurred during launch, the investigation into the two leaks continues. With such an important event as deorbiting the ISS, the U.S. wants to make sure they have reliable options. Something we can hope to receive more updates on in the near future.
Full ISS Transition Plan
The process of deorbiting the ISS takes a lot of planning and consideration from every party involved. Right now, the ISS is entering an era of robust commercial use, taking advantage of the utilities provided by the ISS to develop the capabilities industry needs to move from being dependent on NASA for space station utilization to providing the platform(s) the Agency will need to continue its mission in LEO after the lifetime of the ISS. Commercial crew and cargo transportation are well known examples of the commercial ecosystem supporting ISS, and today they provide the vital lifeline from Earth to the ISS. Keeping the ISS up and running until 2030 is intended to give proper time for the commercial industry and companies like Axoim Space to develop its technology.
As far as the actual deorbit of the station, NASA and the ISS International Partners remain vigilant regarding the safe operation of the ISS. Based on the ISS structural health analysis performed to date, there is high confidence that ISS life can be further extended through 2030. In a NASA report, they commented, “The technical lifetime of the ISS is limited by the primary structure, which includes the modules, radiators, and truss structures. Other systems such as power, environmental control and life support, and communications, are all repairable or replaceable on orbit. The lifetime of the primary structure is affected by dynamic loading (such as vehicle dockings/undockings) and orbital thermal cycling. Each ISS International Partner is responsible for performing life extension analyses for its own modules and structures. NASA, the Canadian Space Agency (CSA), European Space Agency (ESA), and the Japan Aerospace Exploration Agency (JAXA) have completed life extension analyses through 2028. Roscosmos has completed its extension analysis through 2024 and is working on analyzing extension through 2030.
In the nominal scenario, ISS mission control will begin scheduling retrograde ISS maneuvers in the lead-up to ISS deorbit to begin slowly lowering the operational altitude of the ISS. A provided figure shows that these retrograde maneuvers may start at different times depending on solar cycle activity and its effect on Earth’s atmosphere (higher solar activity tends to expand the Earth’s atmosphere and increase resistance to the ISS’ velocity, resulting in more drag and natural altitude loss). This lower altitude results in higher velocity overall. Eventually, after performing maneuvers to line up the final target ground track and debris footprint over the South Pacific Oceanic Uninhabited Area (SPOUA), the area around Point Nemo, ISS operators will perform the ISS re-entry burn, providing the final push to lower ISS as much as possible and ensure safe atmospheric entry.
The ISS will accomplish the de-orbit maneuvers by using the propulsion capabilities of the ISS and possibly the new space tug under development. As far as what’s next, by engaging with industry early in the development phase of CLDs, NASA is helping to ensure that these commercial systems will be safe and will eventually meet the Agency’s requirements. NASA will be able to transfer its knowledge and experience from over 20 years of ISS operations to the private sector, while the companies will be able to quickly mature innovative and cost-effective designs. This public-private partnership for the early phase of CLD development will leverage the strengths of both entities to produce safe, reliable, and cost effective CLDs.
After Axiom, Blue Origin, Nanoracks, and Northrop Grumman have matured their designs and business models over the next 3-4 years, NASA intends to have a second phase of activity whereby the Agency contracts with one or more entities to certify their designs as safe and to purchase services from the CLD provider(s). This second phase, which will be a full and open competition, is similar to the Commercial Crew transportation Capabilities (CCtCap) contracts NASA awarded to SpaceX and Boeing for the Commercial Crew Program. Thus, the Agency is building on the successful legacy of our commercial crew and cargo programs that are currently delivering important research, supplies, and NASA and international partner astronauts to the ISS.
These activities are hoping to enable the development of commercially-owned and -operated LEO destinations that are safe, reliable, and cost-effective. With the introduction of CLDs, NASA expects to realize efficiencies from the use of innovative, efficient, and cost-effective platforms using a more commercial approach to meeting the Agency’s needs in LEO. As commercial LEO destinations become available, NASA intends to implement an orderly transition from current ISS operations to these new CLDs. The transition of LEO operations to the private sector will yield efficiencies in the long term, enabling NASA to shift more financial and personnel resources toward deep space exploration objectives. As both the supply and demand activities mature through the mid-to-late 2020s, NASA will continue to assess readiness to transition to commercial services and destinations through a number of transition indicators, shown in Figure 1. While the top two indicators (CLD readiness and ISS health) are the most critical, the others are important signals to consider for a smooth transition that achieves national goals in LEO. Something we can look forward to in the coming years.
Conclusion
NASA is in the process of trying to determine the best way to deorbit the massive International Space Station. While the initial plan involved using multiple Russian Progress spacecraft for the operation, the agency would be more comfortable if they also had a specially designed space tug for the job. We will have to wait and see how it progresses and the impact it has on the space industry.