The Roswell Report: Fact vs. Fiction in the New Mexico Desert

Corps ML-310/ radiosonde aneroid unit, a metal helix on a rotating cylinder of insulating material, and a 6-volt electric motor which rotates the cylinder.

There are two contacting pens which ride on the cylinder and complete the modulator circuit of the transmitter when they touch the helix. One pen is fixed in position and makes a contact at the same time in each revolution of the helix. This contact is used as a reference point for measuring the speed of rotation of the cylinder. The time that the second pen (which is linked directly to the aneroid cell) makes contact with the spiral, is dependent on the cylinder speed and on the pen position which is determined by the pressure. By an evaluation chart, the atmospheric pressure can be determined as a function of the relative position of the pressure contact as compared to the reference, thus eliminating all rotation effects except short-term motor speed fluctuations.

The operation of this unit is described in detail in Section II, "Operations," of this report, pages 54-63.

Some of the units flown have been made in the shops of the project, while others have been commercially supplied. The following specifications have been set up for performance of the Olland-Cycle:

Pressure range: 1050 to 5 mb.

Temperature range: +30 $ ^{\circ} $ C to -30 $ ^{\circ} $ C

Accuracy: $ \pm $ 0.2 mb.

Readability: $ \pm $ 0.1 mb.

A number of tests have been made on the accuracy of the Olland-Cycle modulator. The tests were of two types. The first was made running the unit at room temperature while the pressure remained constant. In the second, the pressure was varied from surface pressure to about 20 millibars several times at different temperatures. In tests of the first type, the maximum variation of pressure for a given contact pen position was 1.3 millibars in a series of 182 revolutions.

The most comprehensive tests of this type were made with two Olland-Cycles in the same bell jar running for three hours and ten minutes. Due to differences in speed of revolution, different numbers of revolutions were recorded in the time interval, 138 being made by instrument No. L-416 and 181 by instrument No. B-501. No. L-416 was made in the shops of the Research Division and used a Brailsford 6-volt (1 rpm nominal speed) motor, hard-rubber cylinder with 8 turns per inch of .010" nickel wire on a $ \frac{1}{4} $ aluminum plate base. No. B-501 was made by Brailsford and Co. to Balloon Project specifications. It had the same 6-volt motor, a paper base bakelite cylinder with 8 turns per inch of .010" nickel wire and was mounted on a 1/16" sheet aluminum frame.