The first Block I certification engine, which contained the second oxidizer turbopump certification unit, began testing in October 1994.

Engineers involved in the oxidizer turbopump development successfully resolved all of the major technical problems encountered early in development.

Block I incorporates the new phase II powerhead, the single coil heat exchanger, and the alternate high pressure oxidizer turbopump.

For future launches of the Globalstar programme, an additional pyrotechnic valve will be installed on the upper part of the second stage oxidizer tank.

To date, the oxidizer turbopump has satisfied its requirements for total development seconds and the first of two formal certification units has successfully completed its 20 test series.

After injection, up to 4 tonnes of the oxidizer and its vapours, up to 2 tonnes of the fuel and up to 60 kg of gaseous helium can still remain in tanks.

For vehicles where fuel and oxidizer is to reside in a common propellant tank, separated only by a membrane or wall, venting procedures should be designed to prevent the development of excessive differential pressures.