Thread by @LauraEGrego

First reported by @Dimi in the Financial Times, China reportedly has tested a FOBS/hypersonic glider hybrid.

https://twitter.com/Dimi/status/1449462944891346947

(Slow to the draw, but I try not to work on weekends!)

@Dimi Not a space weapon the way you might be thinking. The Outer Space Treaty bars putting nuclear weapons into earth orbit. Stationing nuclear weapons in orbit isn’t something anyone really wants to do anyway. 2009-2017.state.gov/t/isn/5181.htm

Space is a harsh environment and a much less protected spot to keep your dangerous and precious nukes than a storage facility, silo, or sub. Once they’re up there, you cannot maintain them, and an accidental detonation would lead to disaster.

In space, they can be disrupted by debris or targeted by an ASAT. A weapon in a low-earth orbit would be a straightforward target for direct-ascent missile defenses, like the US fields.

The Fractional in FOBS means the orbit is partial: the missile is put in an orbit, but heads to earth before it completes one full 90 minute circuit around the globe. Some legal analysis says that’s not “in orbit” and that FOBS is not banned by the OST.

This test did not carry a nuclear weapon in any case, so it does not explicitly test this law. But I would be interested to see if any country objects. State practice is an important part of interpretation of international law, and how states react matters.

Why would you use FOBS? An ICBM will take between 20 and 40 minutes to its target, depending on distance and whether you use a depressed or minimum energy trajectory. The shortest FOBS trajectory would be closer to the short end of that, comparable with a depressed trajectory

Then why? FOBS is to get around missile defenses. A FOBS can underfly the ground-based radars the US has set up along the expected northerly trajectories of an ICBM or use its essentially unlimited range to come from the south, avoiding them altogether.

That does not mean it will be unseen—space-based infrared sensors will see the engines burn for launch and deorbit, and probably the glide through the atmosphere. There will be no mystery where it came from.

This is not a game-changer; US BMD is not designed to counter China’s existing missiles.

But it could be a hedge against the US eventually making missile defenses work against Chinese (non-FOBS) ICBMs. Given the unlimited nature of US BMD programs and the capability the US has to conduct a disarming strike, US BMD continues to be a concern to China.

However, 1) China’s own experiments with midcourse defenses should inform it well about how remote that possibility is. And 2) China seems very concerned about space-based boost phase defenses, where a FOBS strategy isn’t a game-changer over ICBMs.

I have no int'l law expertise, and would be very interested to hear from @CassandraSteer @GenCounselWolf @Chris_Borgen @KuboMacak @dunc4nbl4ke and others.

There are lots of people posting interesting commentary and analysis, please look/follow/add: @Joshua_Pollack @ArmsControlWonk @baklitskiy @brianweeden @russianforces @wslafoy @bleddb

@Joshua_Pollack @ArmsControlWonk @baklitskiy @brianweeden @russianforces @wslafoy @bleddb I should make clear that I do not know if this was a test of a FOBS system or not, I don't have any information beyond what was reported and I don't think it's clear. This thread is meant to look at some of the technical and strategic issues of FOBS.

China denies this was a test of a nuclear-capable hypersonic missile, instead a test of reusable space craft. Thanks, @nukestrat .

https://twitter.com/nukestrat/status/1450034565138075659?s=20

Here are some questions I would ask to get a better feel for what technology might have been tested. If it was reusable, how was the craft recovered? Or did it crash into the ground? What was the re-entry trajectory? That influences the conditions the payload experiences.

There are ways to de-orbit that are engineered to make sure the craft and cargo reach land safely, e.g. space shuttle, Soyuz and Shenzhou re-entry capsules, X-37B, SpaceX reusable boosters etc. Other de-orbit paths might maximize kinetic energy or precise location at impact.

Also read this thread by Tong Zhao for his thoughts about China's motivations for its pursuit of new strategic technologies

https://twitter.com/zhaot2005/status/1450035573364707331?s=20

And read his report for a more in-depth discussion: carnegietsinghua.org/2020/06/29/nar…

And @james_acton32 's thoughts, esp his agreement that even if this were FOBS/hypersonic glide, it doesn't make the US somehow newly vulnerable.

https://twitter.com/james_acton32/status/1450096504627204099?s=20