"SpaceX will destroy the ISS"

To me, this is probably the Most Annoying Clickbaits on YouTube. Not because it's this one video with one guy pushing it, but a few posters keep posting things like this on how SpaceX is Going to Destroy the International Space Station.

I haven't bothered to look at any of those to see if they get the story right because any click is a reward for posting crap like that. The story is much simpler. Like it or not, the Space Station is showing signs of old age (like that Russian module leaking). NASA has projected it won't last beyond 2030. That means like it or not, the ISS is coming down one way or another. NASA looked at the options and went with a very reasonable option. Contract for what they're calling the US Deorbit Vehicle, and pick a winning bidder with what they judge to have the best chance of safely bringing the station back to Earth, presumably in a very remote part of some ocean.

NASA awarded the contract to SpaceX this week; $843 million to design and build the USDV.  

This spacecraft will dock to the International Space Station in 2029 and ensure the station makes a controlled reentry through Earth's atmosphere before reentering in 2030. The bids were submitted last year and the contract just announced on June 26. 

"Selecting a US Deorbit Vehicle for the International Space Station will help NASA and its international partners ensure a safe and responsible transition in low Earth orbit at the end of station operations," said Ken Bowersox, NASA's associate administrator for Space Operations, in a statement. "This decision also supports NASA’s plans for future commercial destinations and allows for the continued use of space near Earth."

NASA has been working to help initiate a commercial economy in low Earth orbit and has been supporting the few companies working to establish private space stations - presumably with contracts. The concept is that they would contract with these companies to accommodate NASA astronauts as well as astronauts from other countries and space tourists. The goal is to have these private stations operational by 2030 when the ISS will be decommissioned. Having a deadline for ISS availability is expected to help investors decide if they want to invest in these companies.

So how does one decommission the ISS, a behemoth approximately the size of an American football field, with a mass of nearly 1 million pounds (450 metric tons)?

The space agency considered alternatives to splashing the station down into a remote area of an ocean. One option involved moving the station into a stable parking orbit at 40,000 km above Earth, above geostationary orbit. However, the agency said this would require 3,900 m/s of delta-V, compared to the approximately 47 m/s of delta-V needed to deorbit the station. In terms of propellant, NASA estimated moving to a higher orbit would require 900 metric tons, or the equivalent of 150 to 250 cargo supply vehicles.

NASA also considered partially disassembling the station before its reentry but found this would be much more complex and risky than a controlled deorbit that kept the complex intact.

(No mention of considering crashing the station in a place where a million pounds of trash wouldn't be out of place, like San Fransicko or Lost Angeles.)

We don't know what SpaceX proposed but we can make some guesses. Since this is a mission that requires the DV to fire when it needs to for how long it needs to apply thrust, no more or no less, it needs to be what they call a "Category 3" rocket; that is, rockets that have a robust launch history. This immediately implies a Falcon 9. A Falcon 9 is a launch vehicle, though, not something with a robust history of operating in space. That implies something based on the Dragon space craft - probably Cargo Dragon rather than Crew - both of which are developing a good track record of mission success. 

Another option is the "Dragon XL" spacecraft, which SpaceX is designing to supply NASA's Lunar Gateway station near the Moon. This vehicle could conceivably have the propulsive capability to deorbit the station, and, critically, it is being designed to have the capability to remain docked to a space station for 12 months or longer, similar to the requirement for the deorbit vehicle. Therefore, this seems like the most probable choice.

An interesting footnote to this discussion is that NASA originally offered the bidding in two phases: the design phase was "Cost-plus" and the development phase was firm fixed-price. SpaceX chose to do the entire contract as firm fixed-price, and while NASA and Bill Nelson were discussing it as a $1.5 billion job, SpaceX bid that $834 million, saving 44% of what they estimated. 

Image credit: NASA