Controls and maneuverability

A thread of 3 messages, 14 November 1992 to 15 November 1992, in the order they were sent.

#4943 Controls and maneuverability

[unnamed sender] · 14 November 1992

Hi!

Mark suggested that on spacecraft with low maneuverability a
stick and rudder type control system is not necessary.  When you're
moving really slowly, or don't have much agility, you don't really
need a high performance type control panel for low performance
engines.  This is mostly true.

However, the normal traveller spacecraft is capable of at least 1G
acceleration for maneuvering.  Now let's look at a comparable
performance:  The only aircraft *I* know of with a large production
that has a 1 to 1 thrust to weight ratio (hence 1G acceleration)
is the high performance fighter, the McDonnell Douglas F-15 Eagle.
Therefore, those clunky old 1G Type A Free Traders got a whole
hullovalot more maneuverability than most people realize!

The only powered traveller space craft that have less than 1G
maneuver are those equipped with either Mass Drivers, or Ion
Drives.  Even those craft will need some sort of directional
controllers and maneuvering jets.  So, why would one design a
control panel just for those two cases that would require special
training in order to operate them?  If the pilot trained on a
control stick (or one of the other types I mentioned) why bother
changing it?  I don't know for certain, but I'm willing to bet you
that the Skylab, Salyut, Mir, and the proposed Station Freedom all
had/have/will have joystick attitude controllers for the rare times
that the stations need re-alignment.

Traveller space craft that have less thrust than one of today's top
interceptors are the exception, not the rule.  Now, the F-15 may be
capable of 9G turns, so maybe you disagree with me over the
definition of maneuverabilty/thrust.  But, as a student pilot, I
was not allowed to put the Cessna 152 into maneuvers that were more
than 1G (60 degrees angle of bank)  (My CFI had this temper ya
know... :-)  Anyway, I'll tell ya.  *I* wouldn't wanna fly
maneuvers like that without the kind control afforded by a stick or
some similar control system.  1G is a *lot* more than it sounds
like.  If you don't like plane analogies, 1G is more maneuver than
ANY automobile is or will be ever capable of.

Scott 2G Kellogg

#4945 Re: Controls and maneuverability

Seth the Lesser · 15 November 1992 · reply to #4943

Scott 2G Kellogg said:
> However, the normal traveller spacecraft is capable of at least 1G
> acceleration for maneuvering.  Now let's look at a comparable
> performance:  The only aircraft *I* know of with a large production
> that has a 1 to 1 thrust to weight ratio (hence 1G acceleration)
> is the high performance fighter, the McDonnell Douglas F-15 Eagle.
> Therefore, those clunky old 1G Type A Free Traders got a whole
> hullovalot more maneuverability than most people realize!

Huh.  Kinda makes you wonder just what sort of control panel a craft with a 6G
maneuver drive and an agility of 3 or so would have.  Must be something pretty
special.

On the other hand, keep in mind that the forward acceleration of 1G for a Type
A doesn't translate to 1G of *lateral* acceleration; thrusters only get 40%
of normal efficiency parallel to the plates, so that's only 0.4G lateral
acceleration.  You'd know better than I would, but isn't lateral acceleration
more closely related to maneuverability and "crankiness" than forward
acceleration is? 0.4G is an *awful* lot less than the 9G that you say an F-15
can pull in a tight turn.

Seth "the Lesser"
Pardon me if I don't make sense; I've got 30% of a case of the mumps.

#4947 Re: Controls and Maneuverability

Bertil Jonell · 15 November 1992 · reply to #4945

> From: [email removed]
> Subject: Controls and maneuverability
>
> However, the normal traveller spacecraft is capable of at least 1G
> acceleration for maneuvering.  Now let's look at a comparable
> performance:  The only aircraft *I* know of with a large production
> that has a 1 to 1 thrust to weight ratio (hence 1G acceleration)

  Eh, looks like we're back to the old agility vs acceleration thread again:)

  If you are going to compare the maneuverability of a 1G ship and a
jet fighter, you can't use the fighters engine acceleration as a input,
since the fighter uses airfoils to turn, not thrust.

  The comparision should be made between the ship that can do 1G turns and
the aircraft that can do 9G turns (And probably 15G for high-TL hybrids that
mount 6G compensators).

  So while a good scout ship (2G) should be able to outclimb almost anything
TL8 or less (except SAM's:) almost anything including a WWI fighter should
be able to outturn the scout ship.

  (It won't do them any good however, since almost all spaceships mount
turreted weaponry)

> I don't know for certain, but I'm willing to bet you
> that the Skylab, Salyut, Mir, and the proposed Station Freedom all
> had/have/will have joystick attitude controllers for the rare times
> that the stations need re-alignment.

  I'm resonably certain that the Shuttle use a joystick for in-orbit
maneuvering.

> Scott 2G Kellogg

- -bertil-
- --
"Ack! Phht!" - Bill the Prez