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DSL Reference Ballistic Second Stage

The DSL reference second stage is a LOX/LH2 liquid rocket engine propelled system with an initial mass of 200 Mg. This stage is air-launched from the supersonic carrier aircraft at M=2.7, at an altitude of about 20 km, and at a flight path angle of 12°. Ignition of the rocket engines occurs after reaching a sufficient safety distance at M=2.5 and a flight path angle of 10 deg.

Dimensions of the DSL reference second stage are about the size of the ARIANE 5 core stage (diameter 5.5m, overall length 37m). Fairing length is 12 m. The dry-mass of the ballistic stage necessary to reach LEO is estimated to be 19 Mg. The propulsion system is assumed to consist of two scaled SSME with an expansion ratio of 150.

DSL Reference Ballistic Upper Stage Ascent Trajectory

Trajectory simulations for the ascent of the ballistic upper stage have been performed to a variety of target orbits. The diagrams show the state histories of an optimal ascent trajectory into a transfer orbit of Low Earth Orbit. The altitude of the final circular orbit is 400 km, the perigee of the transfer orbit is at 90 km.

The initial conditions are prescribed by the vehicle's state imediately after the release from the carrier aircraft. The trajectory calculation starts with the ignition of the engines at an altitude of 19.7 km, a Mach number of 2.5 and a flight path angle of 10 degrees.

The two scaled SSME engines with nozzle area ratios of 150 provide a thrust-to-weigth ratio of 1.3 at engine ignition. They are throttled back when the vehicle reaches the acceleration constraint of 3.5 g.

Payload Masses of the DSL Reference Ballistic Upper Stage

The resulting payload masses into Low Earth Orbit (LEO), Sun-Synchronous Orbit (SSO) and Geostationary Transfer Orbit (GTO) of the ballistic upper stage are given in the following chart:

The data given in this chart is different from these shown on the DSL General Information Page due to different structural and fairing masses.

The payload becomes 'negative' when the vehicle is directly inserted into GTO. An alternative to deliver payloads into GEO is the ascent via a low earth parking orbit. In this case, the vehicle is inserted into a Low Earth Orbit and an additional transfer stage, which is part of the LEO payload, delivers the final payload into GEO. Such a strategy yields payload masses of about 4 tons into GEO (including the additional mass of the transfer stage).