Dec 5, 2011

Trans Lunar Injection (TLI) Stage


The Polar Satellite Launch Vehicle can be used to launch the spacecraft stack into Geostationary Transfer Orbit (GTO) but then a second rocket impulse is needed to transfer from this orbit into the Lunar Transfer Orbit (LTO) required to complete the mission.
This part of the mission is referred to as the Trans Lunar Injection (TLI) stage and is accomplished using a Star30BP solid motor. The spacecraft is first stabilised by spinning it about its flight axis using a small motor which thrusts in the tangential direction before the Star30BP fires to inject the stack into LTO. A yo-yo de-spin mechanism is used to slow the craft's rotation after the TLI stage is complete, a video demonstrating a yo-yo de-spin can be viewed here. If either the Soyuz Fregat or Falcon 9 launch vehicle is used then the spacecraft stack is placed directly in LTO so the separate TLI stage rocket is not needed.

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