1959-1970-Change

Minuteman Solid Propellant Missile

Minuteman 1 Minuteman 2 with new electronics and new stage 2

MM 1 Electronics (first transistor & digital) MM 1 Inertial Guidance System MM 1 Check out console

Navaho Inertial Guidance used in submarine to pass under polar ice was used for the new minuteman

Minuteman was launched from underground silos

1960 MM 1, Stage 3 Experimental servo actuator with built in movable jet tube servo valve. Torque motor moves “fire hose” squirt to one or other ports to push pilot stage spool, which ports fluid to extend or retract the main hydraulic piston. This was not the selected choice.

1960 MM 1, Stage 3 R&D version with plug in servo valve of flapper control kind.

1960 MM 1, Stage 3 NCU (Nozzle Control Unit) Production Version

Left housing shows opening for plug in location for servo valve and position transducer.

Right housing shows mount to engine and face mounting to NCU

1960 MM 1, Stage 2 Nozzle Control Unit

Servo actuator housing held a piston with shaft connected to an extensible link. The position transducer body below screwed into the housing and it’s core piece into the hollowed piston shaft, the servo valve s plugged into the body. The packaging concept was initiated by Autonetics CA then implemented by Ling Tempco Vaught Dallas TX and proved to be very reliable.

Position transducer and functional diagram

Sine wave excitation was available for the Navaho application of the Linear Position Transducer. For Minuteman it was necessary to chop DC to make AC. The 5 khz frequency generated a lot of noise for other electronics. The center position signal goes to a “null” but not zero. AC output was rectified with a Demodulator with switch transistors rather than diodes as diodes do not work well at low voltage.

NCU at right fits diagonal & upside down from view show, to tilt nozzles for thrust vector attitude control.

Nozzle Control Unit shown with ablative rubber thermal protection

The NCU structure is an aluminum “X” with four arms and center section to hold the hydraulic pump and electronics. There is no hydraulic tubing, actuators and pumps are plugged in and fluid flows through drilled passages. The NCU mounts on the tilting nozzle base through mounts, on side of servo actuator body, shown in prior views. It was necessary to use a vacuum pump to empty the drilled fluid passages then suck in air free hydraulic oil.

1960 MM 1 Stage 1, 2, 3 hydraulic Power Supplies. There was no “ON Switch”, Squib activated batteries a minute before launch. ref

battery power passes through a radio noise filter. There is no pump case, it’s immersed in the bellows reservoir. Output plugs into aluminum X frame. Art Greer and Lou Purpura came up with the packaging concept. These are “compensating” pump where output is automatically controlled to sustain a given pressure by rotating the plate that controls input and output area. The fixed angle pumps rotate at 30,000 rpm.

The computer commands an actuator position, actual position is feedback and subtracted from the command to produce an error which becomes the command to the control valve. Frequency Response tests are critical to prove that a system works properly, Test equipment commands the system at a full range of frequencies and the Amplitude ratio and phase shift measured for assurance it’s within limits. Patterns on an oscilloscope are used by operator. (I was using this method to test the first G-26 booster, the test failed. Unseen check valves in the supply had not fully opened. Determining what was wrong boosted my standing from unknown to expert – putting me in charge of the high temp test lab.)

photo dated 1959 of experimental digital valve

Since a digital computer was used on Minuteman I, there were attempts to develop digital valves and binary segmented servo actuators – without success. After MM 3 I found a way to commanding analog servo valves with digital devices.

1960 MM 1, Stage II Arm/Disarm Switch used on MM II and MM III stage II

Also used on MM III Post Boost as Buyer Furnished Equipment. It had to be shock mounted to protect against high G shocks caused by stage III to Post Boost Vehicle separation joint explosion.

1960 MM 1, inter-stage cable segment. Ground power was used to run hydraulic pumps during check out – prior to irreversible battery activation.

Thrust Vector Control Evolution

MM 1 Tilting Nozzles MM 2 Secondary Injection MX Gimbaled Nozzles

MM 1 control system MM 2 stage 2 Secondary injection control method, injectant produces push on side of the nozzle

Two injector units at left were mounted as shown at right – hot gas nozzles were used for roll control.

Roll valve drivers included an inductive kickback path, to not destroy the transistor.

Injectant not consumed had to be dumped, MM 2 integrated electronic amplifiers used to measure actual flow per injector.

MM 3 Launch Artist depiction of Post Boost MM 3 at Smithsonian H-Bomb warheads at Smithsonian

Looking up at Post Boost Propulsion Looking down on Guidance section – exposed guidance section

Looking down on Guidance section looking up at guidance section looking down on post boost section fitting sections

Post boost contained: Fuel and Oxidizer bellows tanks, 4000 psi pressure bottle, 4 roll, 4 pitch, 2 yaw & 1 Axial bi-propellant engines, 2 axial engine gimbal actuators, arm/disarm switch, interconnecting plumbing wiring and staging connector.

(a) Staging connector and 4000 psi helium tank corner of propellant tank (b) (c) & (d) attitude engines at angle

pre trimmed MM 3 integrated circuit -- huge reduction is size Bi-Propellant valve -- One electrical connector per engine.

The Minuteman 3 program began in 1965 with a letter contract to move out fast, H-bombs, storable propellants, new rocket engine and electronics technology permitted deploying multiple warheads. Don Jones from Space Division and Darrell Landau of Autonetics Division were called upon to write a specification for the Post boost section based on an artist sketch of deploying multiple warheads. The signature date on the above Configuration Control drawing is 1970. This design was refined at the time of the Moon shot. The MM 3 required more advanced technology to cope with much higher shock & G forces and perform mission under computer control from moment of launch. The Minuteman launched one minute after Go. Jones returned to Space Division and Landau continued as supervisor of systems requirement and integration. Autonectics roll ended in 1970 and Landau, out of a job, switched to electronics on how to convert analog controls to digital for better survival under nuclear threat. Lyle Chapin informed Landau that people spent a day in Oberlin asked lots of questions about him – turns out the visit with people in Oberlin was part of a secret clearance check.

In 2007 the US decided to keep this system operational till 2030, our original design goal was for 5 years.

For the rest of the story see www.lanbob.com