Application Summary
With the second flight of SpaceShipOne successfully going beyond the 62-mile target, Brian Binnie claimed the Ansari X Prize for the craft’s designer and founder of Scaled Composites, Burt Rutan, and Paul Allen, who put more than $20 million into the project. Michael Melvill piloted the first flight of the privately funded program, the first of its kind to have put a civilian test pilot into space.

Designing and building such a commercial spacecraft requires the same kind of contemplation that goes into government-funded space programs, such as material selection and testing. Extensive testing was required of the prototype craft during several stages of development. One of the steps was a relatively safe, high-speed taxi test. A specially equipped truck accelerated the SpaceShipOne elevon down range at almost 90 mph, and then abruptly decelerated. Lift was measured with different angles of attack of the elevon.

The second step was performed during a glide test. That event required additional stress measurements on the tail and elevons. And thirdly, in-flight testing included somewhat more critical components, such as the feather locks. Failure of these critical components could place the craft in a feather mode and quickly send it plummeting to the ground.

Potential Solution
In order to acquire critical mechanical and electrical measurements during development, a basic data acquisition system was assembled, specifically intended for the initial tests. It comprised a custom-built computer with external signal conditioning cards, and various other boards. It was relatively easy to modify and customize for lab tests, but it proved to be unsuitable for in-flight tests. The computer was too large and bulky to install either permanently or temporarily, and it added undue weight to the craft. It was also difficult to program and unable to conveniently handle the large amounts of data that were needed to be collected and analyzed.

IOtech’s Solution
Robert Dallons, engineering technician for the design and development group, had the task of finding a superior system to take measurements during flight. He found that the IOtech LogBook data acquisition system fit the application better than the original, computer-card based system. Dallons also purchased the needed signal conditioning hardware, which included a DBK11A high level input card, a DBK16 strain gage expansion card, and a DBK82 thermocouple conditioning cards.

Major advantages of the LogBook are in its size, weight, and power. “The LogBook is considerably smaller and lighter than a full-size computer system, and it conveniently connects directly to the available low voltage dc power commonly used for other systems aboard the craft,” says Dallons. “Also, the LogBook is faster than the old system and is easier to program.” Dallons wrote the required software for data acquisition and personally took the data. In addition, he used Excel spreadsheet software to acquire the data in ASCII format, the IOtech-supplied software to convert it from binary, and other high-end software for data analysis. LogView was used specifically to upload, download, and calibrate the system, which worked well.

The most critical measurements included engine temperatures. The rocket engines are constructed of epoxy carbon composite materials, and although certified safe, they burn longer and run hotter as the craft reaches even loftier altitudes. Other temperature measurements included the wing surfaces to discover the temperature they sustained upon re-entry into the atmosphere. The wings are covered with a special thermal protective coating, and the measurements are made to ensure that the material can take the heat. A thermocouple was placed on the outside protective surface coating of the wing, another was located just below the coating — the interface between the coating and the composite material — and a third measured the temperature on the opposite side of the composite. Additional thermocouples recorded temperatures under the right wing and fuselage.

Accelerometers measured up to 5 gs repeatedly at several different angles, which the pilot, Binnie, and the IOtech equipment sustained without harm. The pressures and temperatures of the oxidizer tanks were continuously logged, and the temperatures were constantly monitored during flight with the IOtech Remote Operation Display. Binnie had to watch the oxidizer temperatures during the flight and manually adjust the temperature to obtain optimal performance.

“The data acquisition system that we had in the space ship was pretty important to us, to manage the details of the propulsion system,” says Binnie. “To get the right performance out of it, we really needed to stay on top of the temperatures and pressures of our oxidizer tank, and that was primarily the pilot’s responsibility — to monitor it on the long, one-hour climb up to altitude. We can modulate the heating by engine bleed air heat from the White-Knight engines and we use the IOtech LogBook data system to give us that feedback. So, basically, we read pressures and temperatures and then we called for more or less heat as we watched the trends, which we controlled manually. It was really important for us to be able to squeeze out all the performance of that system that we could.”

Conclusion
Scaled Composites LLC, Mojave, Calif., designed SpaceShipOne, the first privately funded, successful space ship to make the more than 62-mile trip to outer space. It carried an IOtech LogBook data acquisition system on board, which was located just behind the pilot, Brian Binnie. Binnie monitored engine temperatures on the IOtech Remote Operation Display during the journey in order to make fine temperature adjustments and squeeze out the maximum performance of the engine.

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