In a conference call this morning, Orbital Sciences Corporation announced how it would fulfill its contract commitments to NASA for delivering cargo to the International Space Station (ISS) under a $1.9 billion contract after its launch failure last week.  The company plans to buy one or two third-party launches for 2015-2016 and put an upgraded Antares launch vehicle into service by 2016—an aggressive schedule to play catch up after the Orb-3 mission came crashing back to earth.

Orbital's accident investigation board says its "preliminary evidence and analysis" conducted to date point to "probably" a turbopump-related failure in one of the two Aerojet Rocketdyne AJ-26 first stage engines.  "The use of these engines for the Antares likely will be discontinued," stated Orbital in its morning release.   In responding to a Wall Street question, Orbital CEO David Thompson implied the decision to stop using the rebuilt Soviet-era engines was based on fundamental reliability issues.

The AJ-26 engines provided by Aerojet have a colorful and often-questioned history .  Prior to the Orb-3 failure, AJ-26 engines failed twice in separate incidents during ground testing, most recently in the spring of this year.  Aerojet acquired a group of around 43 original NK-33 engines in the mid-1990s, hardware originally built in the 1960s and 1970s for use in the Soviet moon program.   A first AJ-26 test stand failure in June 2011 at NASA's Stennis test stand was attributed to stress corrosion cracking of 40 year old metal. 

Under NASA's Commercial Resupply  Services (CRS) contract, Orbital has to delivery around 20,000 kilograms of cargo to the space station by the end of 2016. In an unprecedented move, Orbital plans to move one or two launches of its Cygnus cargo spacecraft to a non-Orbital rocket in the 2015-2016 timeframe.  CEO David Thompson said two U.S. and one European launch provider are under consideration for the make-up launches, but would not give specifics.

Cygnus is based upon Orbital's STAR spacecraft bus with a cargo module bolted on the front.  Thompson says the already-built Enhanced Cygnus will carry an average of 3300 kilograms per flight across four flights, meeting Orbital's current contractual obligations. Originally, Orbital planned five flights using the AJ-26-based Antares, but using third-party launchers and an upgraded Antares launch vehicle will deliver more cargo per flight.

Launch operations for the improved Antares rocket would start up at Wallops Island , VA in 2016.  Thompson would not detail what engine or configuration would be used, citing discussions with commercial customers on performance requirements, but speculation has centered on the Russian produced NPO Energomash RD-193.   The RD-193 is a liquid fueled engine using the same fuels as the AJ-26, liquid oxygen and RP-1 kerosene, while providing higher performance.  Planned for use on the Soyuz rocket and already extensively tested, the RD-193 would be new build hardware. 

Alternative speculation has centered on an all-solid fuel version of Antares, stimulated in part by the company's merger plans with solid rocket motor manufacture ATK, but others have pointed out that the current range of safety plans for Wallops Island, VA would have to be significantly reworked given the amount of explosive power involved.

Questions remain as to what launcher or launchers would be used for the Orbital Cygnus stop-gap flights in 2015 and 2016. Orbital says there should be no "material" financial impacts to its finances in 2015, but use of a ULA Atlas V or Delta IV rocket may cost upward of $200 million, once you start figuring in shipping Cygnus and its associated handling equipment and personnel down to Florida and integrating everything on a new vehicle.  And launch providers just don't have spare rockets sitting around waiting for accidents to happen, so there's a question as to how fast one could be built and a launch slot found it at Cape Canaveral.

Use of a more cost-effective SpaceX Falcon 9 could be possible, but SpaceX has a significant launch manifest for the rest of this year into 2015. It is unlikely that a Cygnus would be the payload for the Falcon Heavy demonstration mission, given the additional risk of putting the mission on an untested vehicle.