I believe Vela shut-up shop in 2006. Certainly their website spacetrans.com disappeared in the 2nd half of 2006 and I found nothing more recent elsewhere with a quick web search.
However, their two-stage suborbital system - Sky Lifter carrier aircraft and Space Cruiser spaceplane - is interesting as it has a number of similiarities with WhiteKnightTwo and SpaceShipTwo
whilst being designed/in initial development in the late 90s prior to SpaceShipOne. One feature of note is that despite being a two-stage suborbital system, the spaceplane has both jet and rocket engines.
Following details (and pictures) are taken from an
archived copy of the defunct website. Does anyone have any more info, particularly on how this started?
Sky Lifter
Description: Low-wing load, delta wing, twin tail, first stage, carrier vehicle.
Propulsion: Twin, pylon mounted, JT8D/F100-class turbo-jet engines, thrust 11-18k lb. each.
Crew: Pilot, Co-pilot.
Length: Estimated at 108 ft.
Wing Span: Estimated at 93 ft.
Empty Weight: Estimated at 20-25,000 lb.
GTOW: Estimated at 30-35,000 lb.
Space Cruiser
Description: Medium wing load, double delta wing, twin winglet-tails, second stage, spaceplane vehicle. During initial ascent, the cruiser is carried aloft under the lifter on a pylon.
Propulsion: 3 Nitrous Oxide/Propane, pressure fed, rocket engines (estimated thrust at 20,000 lb. each); and twin, pylon mounted, JT15D-class turbo-jet engines (estimated thrust at 2.2-4000 lb. each)
Power: Onboard jet engine and/or lifter provided (during captive carry); stored energy, probably battery (during boost, free-fall, retro); ram air turbine (during recovery), onboard jet engine (return to airport)
Crew: Pilot, co-pilot
Passengers: Six (6)
Length: Estimated at 61 ft.
Wing Span: Estimated at 38 ft.
Cabin Size: Estimated at 99 in. (inner diameter), 110 in. (outer diameter), 18 ft. length
Empty Weight: Estimated at 15-20,000 lb.
GTOW: Estimated at 25-30,000 lb.
Archived copy of the flight profile is at
http://web.archive.org/web/20050825213241/spacetrans.com/html/flight_profile.htm