Subject: Micro-machining for guided shells

From: [email-masked] (James Kirkpatrick)
Date: 26 Sep 94 15:03:27 MDT

While this isn't exactly recreational metalworking, I have to admire
machinists that can make a gyroscope fit in a shell fuze and survive
the firing cycle!  (This is from another newsgroup).

In article <[email-masked]>,
[email-masked] (Scott Norton) writes:
|> Here is some information on a Navy guided projectile demonstration.
|> My company is supporting the Naval Sea Systems Command office that is
|> managing the demonstration, and my Navy customer said it was OK to put
|> out some information to these newsgroups.  Realize that nothing I say
|> here is either the Navy's or my company's official position, and what I
|> am providing here is meant to stimulate discussion and understanding,
|> not to solicit business or set policy.
|> 
|> -----------------------------------------------------------------------
|> 
|> The Navy is pursuing an Advanced Technology Demonstration entitled
|> "Competent Munitions for the 5"/54 Naval Gun." Its goal is to produce
|> a GPS and inertial navigation system, autopilot, and control system
|> for a gun projectile, which all fits into a NATO-standard nose fuze.
|> This guidance system will convert 5"/54 gun projectiles from unguided
|> to guided rounds, and should be applicable to other projectiles that
|> use the NATO-standard fuze such as the 76mm/62 (Oto Melara) naval gun
|> and the Army and Marine Corp's 155 mm and 105 mm howitzers. It will
|> use micromachined gyroscopes and accelerometers, tightly coupled to a
|> P-code GPS receiver, with control provided by canards on the nose fuze
|> surface. 
|> 
|> The proposer of the ATD and its prime contractor is the Charles Stark
|> Draper Laboratory in Cambridge, MA.  The Gun Division of the Naval Sea
|> System Command is the manager, and the Naval Surface Warfare Center,
|> Dahlgren Division is providing technical oversight.  Draper Lab will
|> be doing system design, development of the autopilot and navigation
|> algorithms, and development of the micromachined inertial components.
|> Lockheed-Sanders is providing the canard control system and actuators,
|> and Rockwell is fabricating the micromachined components.  The GPS
|> contractor is still to be selected. 
|> 
|> As an Advanced Technology Demonstration, this project is intended to
|> take high-risk, high-payoff technology from the "tech base," and bring
|> it to a level of maturity suitable for incorporation into an
|> acquisition program.  The main-line Naval Surface Fire Support program
|> is pursuing long range, GPS-inertial guided projectiles, but not at
|> such a high level of miniaturization and ruggedness.  Because the
|> micromachined inertial components are so small and rugged, they can
|> not just survive gun launch, but can navigate in the gun barrel.
|> Since the projectile knows what acceleration it saw and what velocity
|> it is has, it can better correct any clock errors, estimate Doppler
|> shift of the GPS signal and quickly acquire the GPS satellite.  The
|> micromachined components are part of the ARPA micromachine technology
|> base.  The gun-hardened electronics and GPS comes from the Navy's 60
|> mm Small Caliber Smart Munition program and Army GPS Registration Fuze
|> work.  The canard guidance system was a Navy development a while ago;
|> but when it was developed, there was no guidance or navigation
|> capability that would survive gun launch and could take advantage of
|> the control system. 
|> 
|> If successful, we hope the ATD will lead to a joint acquisition
|> program, since it will produce a guidance unit usable in Army and
|> Marine Corps projectiles as well.  A joint program with the Army will
|> give the Navy and Marine Corps great economies of scale, since the
|> Army's 105 mm and 155 mm inventories are over ten times as large as
|> the Navy's, so you can believe their guided projectile needs would be
|> similarly sized.  The Army is definitely interested. 
|> 
|> We hope to be able to use these projectiles with Relative GPS
|> targeting to achieve a dispersion of only a few meters.  The normal
|> accuracy of P-code GPS is 16 meters, but many of the errors are
|> correlated in space and in time.  So, if a target is located in
|> relation to a GPS receiver, we can calculate what coordinates we
|> should set into the projectile, and it will hit with a few meters of
|> where we want.  There are three restrictions:
|> 
|>  - The distance between the projectile and the other GPS receiver
|> must be within 500 kilometers or so.
|> 
|>  - The time between the measurement of the other GPS receiver and
|> the projectile's arrival on target must be less than about 15 minutes
|> 
|>  - Both GPS receivers must use the same satellites. 
|> 
|> Locating a target relative to a GPS receiver can be done either by
|> having GPS as part of the sensor's navigation (for example, a
|> radar-equipped aircraft with GPS in its navigator), by having the
|> sensor measure the target and also measure a GPS receiver, or by using
|> a surveyed sensor and a surveyed GPS station (the way you would do
|> Differential GPS). 
|> 
|> The project is a three-year, $15-million effort, starting in FY 96.
|> This year, pre-ATD work at NSWC Dahlgren and Draper Lab will begin
|> risk reduction on gun-hardening of the GPS receiver and inertial
|> components in a larger-sized package.
|> 
|> ------------------------------------------------------------------
|> 
|> Please contact me by e-mail if you have any comments or questions, or
|> followup to the sci.military or sci.geo.satellite-nav newsgroups or
|> GPS Digest mailing list.
|> 
|> -- 
|> Scott Norton
|> [email-masked]
|> Defense Technology, Inc.
|> 2361 Jefferson Davis Hwy, Suite 500
|> Arlington VA  22202-3876
|> (703) 415-0200, fax: (703) 415-0206