In order to define flight requirements, a series of ground and airborne simulations was completed by NASA with the support of several field centres. At the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, a Concept Verification Test (CVT) programme was assembled on 25 July 1973, with the aim of simulating high data-rate experiments on the ground to test data compression techniques. These also included data interaction and onboard processing.5 In order to support ESA's development work on Spacelab (and in part to reduce costs in developing experiments that could be flown in space), a general-purpose laboratory resembling the Spacelab configuration was added to the CVT at Marshall in January 1974. After reviewing the original facility, it was suggested that the CVT version should be upgraded to resemble the design of Spacelab more closely. A Preliminary Requirements Review for the new simulator was held on 29-30 May 1974. The CVT Spacelab test programme was established to provide participation by principal investigators who were developing potential experiments for Spacelab missions. This would allow them to test hardware, techniques and interfaces in order to verify their operation prior to assignment to specific missions.
The CVT programme was established at Marshall in 1971 to support that centre's bid for space station concepts that were under development and consideration across the agency, as part of post-Apollo studies. The CVT simulated environmental control and life support systems that would be applicable to future manned spacecraft -ideally a space station, but also with applications to Shuttle and to Spacelab. This desire at Marshall to enter the realm of manned space flight conflicted with the Houston field centre's management and mandate. This often led to contention with
Houston, of the type that surfaced over the previous decade in both the Apollo and Skylab programmes, and which would not be resolved for some time. With Marshall developing the CVT for space station, and Houston arguing for total payload control for the Shuttle, including Spacelab, there were disagreements over how the CVT could help with the development of the "Sortie Can'' that became Spacelab.6
Several CVT simulations were completed from 1972, related to developing the facility and future life support systems, but those specifically Spacelab-related were:
CVT Test No. 1 (Jan 1974) with experiments conducted in ionospheric disturbances, atmospheric cloud physics, metal alloy preparation, high-energy astronomy and super fluid helium.
CVT Test No. 2 (Spring 1974). Little information is available about this test, other than the date it was conducted.
CVT Test No. 3 (15-19 Jul 1974) with an integrated life sciences mission planned and conducted by scientists from the Ames Research Center. The objectives were to demonstrate the protocols of each candidate experiment, module housing units, the rack-mounted equipment and other techniques.
CTV Test No. 4 (16-21 Dec 1974) was a five-day simulated Spacelab mission with eleven materials sciences experiments that the four female crew members had developed. These four women, all employees of Marshall Space Flight Center, were Ann F. Whitaker, Carolyn S. Griner, Mary Helen Johnston and Doris Chandler. This simulation provided a wealth of data on the benefits of having a scientifically trained crew aboard the facility to identify and repair minor malfunctions. In the 1976 report of this test, it was stated: "The value of the well trained scientist crew was emphasised during the test. Had it not been for the extremely knowledgeable science crew, two experiments at least would have been lost early in the simulation. [They] were saved by their knowledge of both the hardware and the science that was to be obtained.''7
CVT Test No. 5 (10 Aug 1975) was a multi-discipline, multi-centre simulation, which also provided valuable information on the standardisation of hardware, crew training, communication requirements and procedures for dealing with equipment failures.
At this time (1975), funding for the CVT programme was a serious issue. Experiments were under development from a variety of NASA centres, but funding for the test missions to evaluate them came from the Office of Manned Spaceflight. The Deputy Associate Administrator, John E. Naugle, issued a memo asking for additional funding (and further simulations) to the Directorates of Science, Applications and
Manned Spaceflight, but their replies were very negative. Other facilities and simulations had superseded the CVT programme and this response signalled its demise, although two other planned simulations were completed first.
CVT Test No. 6 (17-21 Nov 1975) was a materials sciences simulation to determine whether a team of scientists, with moderate experiment operations training, could operate a package of experiments "in orbit". During the test, they were monitored via downlink TV and two-way voice communications by a team of principal investigators.
CVT Test no 7 (15 Jul 1976) was the final CVT simulation and used a high-energy cosmic ray balloon experiment to gather scientific data.
In the NASA Spacelab history, author Douglas Lord stated that the CVT "had provided very useful information and operational experience, [but] the program fell victim to the vagaries of organisational and budgetary life."8 At the same time as the CVT programme was running, another series of Spacelab simulations was being conducted, with more participation by the scientist-astronauts.
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