Re: Sea Launch to Top Atlas
- From: "Josh Hopkins" <hopkins@xxxxxxxxxxxxxxxx>
- Date: Thu, 28 Apr 2005 01:14:47 -0600
"Ed Kyle" <edkyle99@xxxxxxxxxxx> wrote in message
> I count these "partial" failures as failures simply
> because they fall short of being called successes.
> I haven't been able to find a partial success/failure
> figure of merit that I can be comfortable with. The
> Apstar 5 launch vehicle, for example, only provided
> roughly 96% of the planned total delta-v. Could we
> say it was 96% successful? That doesn't work because
> the launcher could have provided 75% of the planned
> total delta-v (and been "75% successful") and still
> failed to make orbit! And we certainly wouldn't
> call a launcher that blew up one minute into flight
> "5% successful"!
We wrestled with this several years ago when we re-worked the AIAA launch
vehicle guide. We came up with the following definitions: (approximately,
from memory - they're in the "How To Use This Book" section if you want to
look them up).
To qualify as a success, a launch vehicle must deliver the payload intact to
its intended orbit, within normal or predicted tolerances.
A partial failure was defined as a mission which did not meet the criteria
for success, but in which the spacecraft is delivered to an orbit from which
it can still perform all or part of its mission, for example because the
unplanned orbit is tolerable or because on-board propulsion can be used to
get it to the correct orbit.
Anything else is a failure.
We applied these criteria to nearly every launch vehicle failure that's ever
happened (the exceptions being from the handful of launch vehicle families
that retired long before the book came out), and they work pretty well.
There are still some grey areas, particularly demo flights which
underperform while carrying dummy payloads owned by the same organization
that operates the launch vehicle. It can be difficult to objectively define
a partial vs full failure in that case.
We also decided that we needed to provide sufficient descriptions of each
failure/partial failure so that people could make up their own minds about
how they wanted to classify a given mission. Writing the failure summaries
was one of the most interesting parts of the project.