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Dr. Daniel Opila

Orbital Sciences Corporation

*Note: This page is my own work, Orbital's official site is*

Orbital is a medium-sized aerospace company based in Dulles, Virginia near Washington DC. They make commercial and military satellites, small and medium launch vehicles, and various other random projects for NASA and the government including various types of missile target simulators.

Ground Based Midcourse Defense

Me and my instrumentation buddy
Me and my instrumentation buddy.

One of my major projects was for the Ballistic Missile Defense system. As part of the continuing system development and reliability tests, several of the older boost vehicles were test fired at ATK Thiokol in Promontory, Utah near Salt Lake City. My main responsibility was coordinating, specifying, installing and verifying several hundred sensors for each test. I was in charge of instrumentation for frequency sweeps of the nozzle thrust vector actuation (steering) system. I also built a relatively cheap, semi-disposable 6-DOF measurement system for nozzle motions. During firing, the motor case expands relative to the nozzle hinge points, making it difficult to estimate nozzle angles. The hydraulic actuator engineers wanted to verify they were indeed pointing the nozzle as requested for steering. The measurement system had to fit under the existing heat shield (for obvious reasons) and be small and flexible enough to fit with the existing equipment. I used 6 string potentiometers with appropriate geometry and math to back out the 6-DOF nozzle motions. A seventh potentiometer provided redundancy for a failure of any of the others.

Installing my 6-DOF measurement system.
Installing my 6-DOF measurement system.

For these "static fire" tests, the solid rocket is strapped down in a concrete bunker and fired rather than actually launching, as shown in the picture below. Orbital's logo is visible in red on the booster. The rocket is a little over 4 feet in diameter and weighs more than 50 tons. The building is actually a concrete bunker built into a hillside with a retractable roof. All the setup occurs "inside" and when ready to fire they retract the roof and open the garage door at the back. At the front of the rocket is a yellow and red steel structure that measures thrust, the other mounting points move to assure the loads are transferred to the measuring device. The aluminum foil-like structure to the right of the flame plume is the quench system, which injects water into the motor after firing to preserve the nozzle condition at the end of the test. The sand at the bottom of the picture is added on test day to protect the underlying concrete, which would otherwise be scoured away.

More Background

Installing my 6-DOF measurement system.
Turning wrenches.
A static fire test image
Test Firing a Solid Rocket Motor

This part of the missile defense shield is called Ground Based Midcourse Defense (GMD). The system attempts to intercept warheads after their boost phase and before they re-enter the atmosphere (midcourse) using interceptors launched from silos (ground-based). Other components of the missile defense shield attempt intercept during other phases of flight, like the airborne laser which destroys the missile during its boost phase.

Ballistic Missle Defense is a huge program that involves all the major defense contractors. On GMD, Boeing is prime contractor, Raytheon builds radars and kill vehicles, Northrop provides battle management, and Orbital builds boost vehicles. This project tested a boost vehicle.

They also test fire the space shuttle solid rocket boosters at a nearby test site, as seen December 4th, 2008 ATK THIOKOL static booster test fire video. These tests are quite an experience and there is nothing like being there. I spent weeks at a time there during these tests, which at times was a walk through history. Lots of stuff still exists from the early days of the space program and ballistic missiles. We stored our equipment in the test site for the original Minuteman missiles.

Hubble Robotic Servicing Mission

I was initially hired at Orbital to work on NASA project to send a robotic repair mission to the Hubble Space Telescope. Orbital was contracted by Lockheed to build the docking system that would connect the robotic vehicle to the telescope. I started out designing a motor and control system for the latch mechanism, which would loosely dock with spring-loaded catches before a motorized hard docking. I wrote motor specifications, coordinated with Lockheed engineers who would also be using our motors, and served as the technical contact for our motor supplier.

Huble Robotic Servicing Mission
Hubble Robotic Servicing Mission
Huble Robotic Servicing Mission
Docking simulation. Spring loaded fingers (red) try to capture
3 bars (circles) on the telescope.
Apollo Probe-Drogue Docking System
Apollo Probe-Drogue Docking System

It became clear someone needed to study the docking event in detail, so I started doing that. Hubble is fairly delicate, so there was a fine line between docking speeds fast enough to assure initial capture and slow enough to avoid damage. I conducted two vehicle 6-DOF flex-body simulations of the docking event to accurately predict loads and specify guidance tolerances for docking. I went to Marshall Space Flight Center for a full-scale simulation with a hydraulic hexapod initially used for the Apollo program.

One of the original Apollo "Probe-Drogue" docking mechanisms between the Command Module and Lunar Lander sits on a pallet in the closet next to the test bay. Comparing it to our docking system 40 years later, those Apollo engineers were really good.

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