PARIS — The European Space Agency on Oct. 24 postponed indefinitely the planned Nov. 18 launch of its intermediate experimental vehicle (IXV) — designed to make a suborbital equatorial flight to test re-entry technologies after launch aboard Europe’s Vega rocket — following concerns for range safety as Vega passes over the South American spaceport.

Stefano Bianchi, head of launchers for the 20-nation ESA, said discussions with the French space agency, CNES — which is Europe’s “launching state” in legal terms as host to the Guiana Space Center — are likely to continue “for a few weeks” before an acceptable flight route is determined.

Given the flight manifests of Europe’s heavy-lift Ariane 5 and medium-lift Europeanized Russian Soyuz rockets in December, the Vega IXV launch may be pushed into early 2015, Bianchi said.

“We are going to do our best to get an early slot but the Arianespace manifest is fixed,” Bianchi said.

In an interview, Bianchi said the specific concern is that Vega’s second and third stages, both solid-fueled, will be unpressurized and in low altitude over French Guiana territory during the flight’s first minutes after liftoff.

The Ariane 5 rocket carries two large solid-fueled boosters, but both are ignited at liftoff. For Vega, a flight anomaly that forced the vehicle’s destruction would pose potential hazards from the vehicle’s fully fueled second and third stages. The vehicle’s fourth stage is liquid-fueled.

“We need to perform some additional studies,” Bianchi said. “There is a formal process at CSG [the Guiana Space Center spaceport] that must be followed, and they need to run their models of the flight, especially with respect to short-range safety and the fragmentation models associated with that.”

Bianchi said it is only natural that range safety authorities, presented with an unprecedented launch profile for a relatively new vehicle — this will be Vega’s fourth flight — would want to pay special attention to the performance required of Vega.

The nearly 2,000-kilogram IXV, a lifting-body vehicle 5 meters long and 2.2 meters wide, is already months late due to a range of issues, including finding a solid Vega flight date.

For the flight, Vega will carry IXV to about 320 kilometers in altitude, leaving it with enough energy to climb to 450 kilometers before descending and re-entering the atmosphere at an altitude of 120 kilometers. A parachute landing is scheduled about 100 minutes after liftoff.

Bianchi said it was not clear why ESA and CNES had not resolved outstanding range-safety issues long before now, given that the mission characteristics have been known for some time.

CNES did not immediately respond to requests for comment on IXV on Oct. 24.

Peter B. de Selding was the Paris bureau chief for SpaceNews.