does NASA ever plan to launch backup hardware, if something goes wrong?

I have some rough notion that for many space probes, NASA builds a flight unit, and a non-flight unit to have on earth that's used to test command sequences, experiment with recovery options, and all the things you might want "hands-on" hardware for. My question is predicated on that being the case - else it makes no sense.

I'm wondering if, in the event of some catastrophe such as a launch accident, loss of the flight-unit en-route, etc, there are ever emergency plans to launch the ground unit (assuming it can easily be made flight-worthy). Since all the effort to design and build it has already happened, maybe it would be down to launch and ongoing mission costs. It would be obviously a much worse outcome than if everything went properly, but better than outright loss of the mission with lots of money sunk and no return if the worst happens.

Of course you wouldn't want to lose the backup for the same reason as the first, but sometimes it's independent (e.g launch accidents), or sometimes they might figure out the problem, and be able to make an easy workaround on the other one.

Submitted October 15, 2016 at 10:39PM by geezbike52 http://ift.tt/2eb0q2P