Clark Lindsey points out that the SpaceX Falcon is making steady progress toward first flight. Among all the other milestones noted, I found this one little bit extremely significant:

Regulators gave them “approval to fly the rocket with only thrust cutoff, rather than explosive termination.”… “[This] improves hazardous procedures in transportation, on the launch pad and particularly on recovery of the first stage.” This [was] allowed “due to the all liquid fuel configuration and six-fold valve redundancy.”

As far as I’m aware, the only previous launch system that received permission to fly without range-safety destruct was the SET-1 launch by the American Rocket Company in 1989. The general philosophy has always been that range safety must be able to not only terminate thrust, but destroy the vehicle, should it go out of control. Rockets have always had such range safety devices, and are unique among all other transportation systems in that regard. No ship, train or plane has had devices on board every trip whose sole purpose is to destroy the vehicle.

If SpaceX has gotten permission to launch without it, with only thrust termination, this may be a first for a liquid-fueled rocket (the American Rocket vehicle was a hybrid, with solid fuel and LOX). The big advantage, as it points out, is that there are now no pyrotechnic (explosive) devices on the vehicle, at least not for that purpose, which eliminates some of the steps in launch processing, and post-launch safing, and reduces one of the hazards associated with ground handling (not to mention greatly enhancing the probability of getting the first stage back, even in the event of a mission failure).

Getting such permission is obviously much more important for a reusable vehicle, which the Falcon first stage is advertised to be. They don’t want to have to destroy the vehicle just because it isn’t following the prescribed trajectory, if they continue to have control over it, because they want to get it back.

This is a key breakthrough in reducing launch costs. Let’s hope that it presages the future.