Re: Truck stopping distances?

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 12:50 -0500 03/01/2002, David Bowman wrote:

>  I wonder if NASA
> ever thought of using a big tailhook & strong cable on the runway?
> They must have.  Maybe the jerking would be too destructive to the
> shuttle's airframe?
I'm sure they did, but I'm just a sure that they quickly realized
that for this particular application the tailhook approach wasn't
practical. The Navy, which has been using tailhooks on airplanes for
at least 70 years, has learned that, as the landing speed increases,
the increase in structural strength required for the airplanes to
survive repeated carrier landings adds a significant weight penalty
and subsequent performance penalty to the design. In fact (although
they don't like to admit it) some of the best Air Force combat
aircraft were originally Navy aircraft, designed to have high
performance characteristics in spite of the weight penalty demanded
by the carrier landing requirement. They took these effective designs
and removed the extra weight required by the carrier landings and
ended up with a really superior performing aircraft.

Given the high landing speed of the shuttles, the extra weight
required to enable it to operate with a tailhook would add probably
millions of dollars to the cost of each launch, just to pay for the
fuel to haul that dead weight into orbit. furthermore, since it is
unpowered on landing, it would be unfortunate if it suffered the fate
of many Navy aircraft on landing--hook skip. As it bounces along the
deck, the hook can and often does skip over a wire (that's one reason
they have several) but with power, the pilot simply adds power and
takes off for another try. Not possible with the shuttle.

The shuttles do have a slowing device that works well, once the craft
is below a certain maximum speed, and that is a drogue parachute,
which can be almost as effective as thrust reversers on a passenger
aircraft.

I think the best thing that NASA has found to help keeping the brakes
on the shuttle from burning out is a very long runway--as much as
20,000 feet, that allows the shuttle to coast to a stop with minimum
braking.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

Let's face it. People use a Mac because they want to, Windows because they
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