The US Air Force (USAF) has invited domestic companies to bid for the second phase of the Launch Service Procurement programme.
A request for proposals was released by the Space and Missile Systems Center and the National Reconnaissance Office for the purpose of competitively awarding the contracts.
The firm fixed-price indefinite-delivery requirements contracts will be awarded to two firms for national security space launch service procurements from the fiscal year 2020 to 2024 for missions launching until 2027.
Interested companies will take part in an open competition for the procurement contracts.
USAF Secretary Heather Wilson said: “We must move forward now. We are answering Congress’ 2014 directive to transition off the Russian-made RD-180 rocket engine.
“The industrial base is ready and we will keep our most demanding national security space orbits on track.”
Through the competitive process, the USAF aims to secure assured access to space and to end dependence on the Russian RD-180 engine.
The process will allow the service to benefit from prototypes developed under the rocket propulsion systems agreements and launch service agreement development contracts.
USAF Acquisition, Technology and Logistics Assistant Secretary Dr William Roper said: “This strategy harnesses the commercial launch industry to meet the more demanding national security space launch needs.
“With the Congressional mandate to transition away from reliance on non-allied rocket propulsion systems and the planned Delta IV retirement, the Space and Missile Systems Center developed an acquisition strategy to meet national security space launch requirements for the future.”
In October, the USAF awarded contracts totalling $2.3bn to Blue Origin, Northrop Grumman Innovation Systems and United Launch Alliance to develop rocket launch systems for national security missions.
According to the military branch, the contracts are intended to ensure the launch systems of these companies are able to meet the national security space requirements.
In addition, SpaceX received contracts over the last two years to deliver nine launch services using its Falcon 9 and Falcon Heavy launch vehicles.
The company launched the first of the nine missions in December last year.