The Antares booster set to lift off on Sunday evening is a re-engineered version of a launch vehicle that exploded spectacularly after launch nearly two years ago.
The key change is the replacement of two Aerojet Rocketdyne AJ-26 engines in the first stage with RD-181 engines produced by NPO Energomash of Russia. The new engines are powered by liquid oxygen (LOX) and kerosene.
The AJ26 motors were refurbished NK-33 engines left over from the Soviet Union’s manned lunar program of the early 1970’s. The failure of a turbo pump in one of the engines was blamed for an October 2014 explosion that destroyed a Cygnus cargo ship bound for the International Space Station.
Following the accident, the company decided to abandon use of the aging AJ26 engines, one of which had failed on a test stand prior to the ill-fated launch. Orbital ATK had already begun the process of finding new engines for the Antares because the supply of refurbished AJ26 engines was limited.
RD-181 engines are more powerful than the AJ26 motors they replaced. The additional power will allow Antares to life more than 7,000 kg (15,432 lb) to low Earth orbit, an increase over the 6,120 kg (13,490 lb) capacity of the previous variant.
This cargo flight will use Orbital ATK’s CASTOR 30XL engine for the second stage. Smaller CASTOR 30A and CASTOR 30B engines have been used on previous flights.
Antares is a product of several nations. In addition to Russian engines, the first stage is produced in Ukraine by KB Yuzhnoye and Yuzhmash and outfitted with Orbital ATK avionics.
The new Antares rocket will be carrying an enhanced Cygnus cargo ship on Sunday. The pressurized cargo module on the enhanced variant has a volume of 27 cubic meters and is 50 percent longer than the one on the standard version. The spacecraft also has larger solar arrays.
Cygnus will carry 2,425 kg (5,346 lb.) worth of cargo to the space station. Space station crew members are expected to load the ship with 1,687 kg (3,719 lb.) worth of trash and unneeded equipment that will be burned up when Cygnus burns up in the Earth’s atmosphere.
This will be the sixth visit by Cygnus to the space station for NASA. That total includes one demonstration mission and five commercial flights. Two Cygnus missions were launched by United Launch Alliance’s Atlas V booster while Antares was grounded.
Cygnus’ pressurized cargo module is produced by Thales Alenia Space in Italy. Orbital ATK supplies the service module.