I have been following the X-37B for some time and was pleased to see that it was successfully launched into orbit yesterday. Being a military project the spaceplane is clouded in mystery. One question I had was how do they intend to launch the operational version? If they want a responsive launch system conventional rockets are out as they can take months to organise.
Now we may have the answer, the USAF is planning a reusable booster:
Plans to begin technology development for a reusable booster system to replace its existing expendable launch vehicles beyond 2025 are being finalized by the U.S. Air Force.With the Air Force facing escalating costs on the Evolved Expendable Launch Vehicle (EELV) program, the new system offers the promise of cutting launch costs more than 50% by combining a reusable first stage with expendable upper stages. The booster would take off vertically and return to a runway landing at the launch site…….The plan calls for replacing the Atlas V and Delta IV with two versions of the RBS: a single reusable first stage and expendable cryogenic upper stage for medium-lift missions; and two reusable boosters, cryogenic core stage and upper stage for heavy-lift and growth missions. Initial operational capability is set for 2025, with the EELVs being phased out in 2030 once the Air Force is comfortable relying on the RBS, he says.
Remember the current EELVs have a similar payload capacity as the Space Shuttle. NASA may have abandoned large reusable launch vehicles but the Air Force hasn’t.