Planned launch of Pegasus XL rocket was scrubbed today due the technical problems and poor weather.

It passed over 25 years since 1990, when Orbital ATK presented their Pegasus  rocket system. Launched from the flying mother plane, rocket was sign of possible change of approach to easy access to space. After all these years rockets launched vertically from the ground are still covering most of the demand for launch vehicles. Mission of Pegasus XL planned for today could remind advantages of this kind of vehicle. Unfortunately launch was scrubbed due the technical problems.

This mission was first after lasting three years break. Orbital ATK was ready to resume flights and mission of CYGNSS (Cyclone Global Navigation Satellite System) contracted for NASA was planned as beginning of return to market for Pegasus – company already planned next mission for 25th June 2017  from Kwajalein Atoll with ICON satellite under the fairing.

Today L-1011 mother plane took off from from Runway 13 at the Skid Strip (cape Canaveral) at 12:39 UTC. F-18 plane with installed cameras and live broadcast operator started to chase L-1011 to provide live broadcast from the event. Eight CYGNSS satellites remained encapsulated inside payload fairing of Pegasus XL installed on special adapter designed and manufactured by Sierra Nevada Corporation. Crew of  Stargazer set course for East; after reaching correct altitude plane started maneuver to reach drop zone with correct course and on planned altitude. At 12:56 UTC L-1011 was already flying over 10000 m above Atlantic and after next five minutes it was going to enter drop zone (65 km x 16 km) around 160 km East from Daytona Beach. Unfortunately due the clouds and heavy rains launch was halted and postponed for around 90 minutes, when weather forecast predicted more favorable conditions. Finally, nine minutes before planned drop at 13:21 UTC, eight satellites inside fairing were switched to internal power. Just before 13:30 UTC crew members started to report problems with unspecified hydraulic pump. Specialists from ground control center and L-1011 crew members were talking about pump pressurizing system of deployment of Pegasus. Drop of the rocket was already delayed at that moment, crew members were reporting that after multiple tries of reinitializing pump manually it still is not working correctly. Specialists from ground control did not decided to scrub the mission but end of the launch window at 14:19 UTC was still getting close. Next drop attempt was set for 14:05 UTC. At 13:51 UTC weather forecasts became favorable enough to switch CYGNSS satellites to internal power two minutes later. Even hydraulic pump starts to operate nominally at 13:55 UTC, but again weather interrupted in dropping the rocket – clouds were moving again into drop zone. At 14:07 UTC mission became set as scrubbed and L-1011 started its flight to Cape Canaveral. It landed without any problems, with rocket and payload in perfect condition, at 14:44 UTC.

CYGNSS is result of cooperation with the University of Michigan, Southwest Research Institute of Texas, Surrey Satellite Technology of Colorado and NASA Ames Research Center. Program started in 2012 thanks to donation given by NASA ($152 million). Planned orbit for satellites is about 500 km -deploying will be conducted from adapter made by Sierra Nevada Corporation providing separation of each satellite with speed of 1 m/s.  Satellites were built by Southwest Research Institute with planned service life at 3 years. GPS system necessary for correct research was Surrey Satellite Technology Ltd, solar panels are product of EMCORE. Satellite is based on CNC aluminium parts bolted together and combined with honeycomb structure. Mass of each satellite is 27.5 kg. Satellites are equipped with  Thermal Control System (for active cooling control), ADCS (Attitude Determination and Control Subsystem) for steering and stability control, EPS (Electrical Power Subsystem) providing battery charging without jamming and interrupting of observation systems (power required for operating is 38.3 W). Communication will be performed with S band transmitter with 4 Mbit/s speed for downlink and 2 Kbit/s uplink speed. Scienctific equipment is DDMI (Delay Doppler Mapping Instrument) for ocean surface monitoring. It uses scattered signalfrom GPS satellites to create DDM (Delay Doppler Map). Device was designed and made by Surrey Satellite Technology US LLC.

Pegasus was presented by Orbital ATK in 1990 as air-launched rocket for LEO missions. It was developed mainly for small satellites, due its payload capacity limited to 1.18 m by 2.13 meter with maximum weight at 443 kg. It is known as first winged vehicle able to reach 8 Ma and first commercially designed and manufactured launch vehicle. Launch procedure requires delivering rocket under Stargazer L-1011 plane to altitude of 12000 m.  Next it is dropped from plane and after about 5 seconds solid fueled Orion-50SXL engine is turning on. On altitude of 61000 m first stage with wings and tail is separating and Pegasus reaches hypersonic speed. Second stage engine, Orion-50XL is turning on for 1 minute and 18 seconds. Second stage is separating, payload fairing is jettisoned when Pegasus is reaching space.  Pegasus starts Orion-38 engine powering third stage for 64 seconds. Pegasus is reaching LEO and is ready for deploying payload. Rocket can be equipped with HAPS fourth stage with propulsion fueled with hydrazine.

For CYGNSS mission Orbital ATK decided to use Pegasus in XL version. It is long for 17.6 m and weighs 23130 kg. Rocket replaced regular Pegasus after introducing in 1994.  First two stages were stretched and wing was reinforced due the increased mass. Payload fairing has diameter of 1145 mm and length of  2138 mm.