http://www.tbs-satellite.com/tse/onl...c_pegasus.html

OSC plans to equip Pegasus XL with two turbojets. Once released at 12000
m altitude the Pegasus Turbo will be accelerated by its turbojets to
reach 30000 m altitude at over Mach 4. OSC claims the 30.8 t Pegasus
Turbo will be 125% more powerful than Pegasus XL and could orbit 1000 kg
in LEO.