MADEFAST Design, Trdeoffs, and Affordability

dwhitney@MIT.EDU (Dan Whitney)
Message-id: <9403071323.AA01989@MIT.EDU>
Date: Mon, 07 Mar 94 08:23:15
From: dwhitney@MIT.EDU (Dan Whitney)
To: leifer@sunrise.stanford.edu, <bajcsy@central.cis.upenn.edu>,
        Bill Birmingham <wpb@eecs.umich.edu>,
        Susan_Finger@WYVERN.CIMDS.RI.CMU.EDU, rfr@cs.utah.edu,
        fertig@rpal.rockwell.com, martin@rpal.rockwell.com, davis@ai.mit.edu,
        sticklen@cbs.msu.edu, mcdowelj@cps.msu.edu, gruber@HPP.Stanford.EDU,
        fikes@HPP.Stanford.EDU, rz@cs.cornell.edu, cohen@cs.utah.edu,
        elks@msg.ti.com, ecks@msg.ti.com, fbp@andrew.cmu.edu, terk@cs.cmu.edu,
        weber@eit.com, mcguire@eit.com, dbrown@cs.utah.edu, sbj@wimpy0.psu.edu,
        wysk@ieman.tamn.edu, jln@draper.com, morgenstern@dri.cornell.edu,
        dwhitney@MIT.EDU, marty@eit.com, wachter@itd.nrl.navy.mil,
        "Glenn A. Kramer" <gak@eit.com>, cutkosky@sunrise.stanford.edu,
        petrie@sunrise.stanford.edu, toye@sunrise.stanford.edu,
        hong@sunrise.stanford.edu,
        "Greg Twiss" <greg_twiss@qm.is.lmsc.lockheed.com>,
        Kevin Lyons <klyons@cme.nist.gov>, Pradeep Khosla <pkk@arpa.mil>,
        "Peter F. Brown" <brown@cme.nist.gov>, Mike McGrath <mcgrath@arpa.mil>,
        kumar@central.cis.upenn.edu
Subject: MADEFAST Design, Trdeoffs, and Affordability
Cc: Bill Birmingham <wpb@eecs.umich.edu>, Susan_Finger@WYVERN.CIMDS.RI.CMU.EDU,
        rfr@cs.utah.edu, fertig@rpal.rockwell.com, martin@rpal.rockwell.com,
        davis@ai.mit.edu, sticklen@cbs.msu.edu, mcdowelj@cps.msu.edu,
        gruber@HPP.Stanford.EDU, fikes@HPP.Stanford.EDU, rz@cs.cornell.edu,
        cohen@cs.utah.edu, elks@msg.ti.com, ecks@msg.ti.com,
        fbp@andrew.cmu.edu, terk@cs.cmu.edu, weber@eit.com, mcguire@eit.com,
        dbrown@cs.utah.edu, sbj@wimpy0.psu.edu, wysk@ieman.tamn.edu,
        jln@draper.com, morgenstern@dri.cornell.edu, dwhitney@MIT.EDU,
        marty@eit.com, wachter@itd.nrl.navy.mil,
        "Glenn A. Kramer" <gak@eit.com>, cutkosky@sunrise.stanford.edu,
        petrie@sunrise.stanford.edu, toye@sunrise.stanford.edu,
        hong@sunrise.stanford.edu,
        "Greg Twiss" <greg_twiss@qm.is.lmsc.lockheed.com>,
        Kevin Lyons <klyons@cme.nist.gov>, Pradeep Khosla <pkk@arpa.mil>,
        "Peter F. Brown" <brown@cme.nist.gov>, Mike McGrath <mcgrath@arpa.mil>,
        kumar@central.cis.upenn.edu

I'm glad to see the "design" part of the program starting to take some 
shape.  I'd like to add some other considerations that may stretch the 
group a little but are a basic part of realistic design and may get 
ARPA's attention:

The specifications for a seeker include pointing accuracy and bandwidth.  
These together mean that it should be able to find and lock onto a 
target and keep hold of it even if it moves rapidly.  It should also be 
able to report the target's heading in two angle dimensions accurately, 
both when the target is apparently stationary and when it is moving.  It 
should also be able to do this when the target is dim and hard to 
detect.

These requirements "flow down" to particular design parameters like 
gimbal motor torque, servo gain and damping, gimbal stiffness and mass, 
rate gyro sensitivity,  bearing runout, sensor sensitivity (hence size 
and weight), and assembled tolerances (do the two gimbal axes intersect? 
do they intersect at the center of the sensor, etc.)

There is an overall diameter and weight limit as well.  These limits 
make it hard to meet the requirements above.  A cost limit will be even 
harder to meet.  

Altogether this mixed set of requirements will require tradeoffs to be 
made between cost and performance.  This is a basic trade which is 
little practiced in DoD work, though it is the main driver in commercial 
work.  Developing collaborative tools to do tradeoffs would be a big 
contribution as DoD strives to define what "affordability" means.