It’s Showtime for Revamped Antares Booster

Antares vertical on the launch pad on Wallops Island. (Credit: Orbital ATK)
Antares vertical on the launch pad on Wallops Island. (Credit: Orbital ATK)

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.

Credit: ATK

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.

Cygnus approaches ISS (Credit: NASA)
Cygnus approaches ISS (Credit: NASA)

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.




  • Snofru Chufu

    I call Antares launcher a bad, strange design if a (by comparison) low performance
    second stage (Isp-wise) is placed on high performance first stage, in respect
    to maximize payload mass fraction of launcher. Normal procedure is just the

  • passinglurker

    Heh if you think that’s bad you should see india’s PSLV…

    Anyway you call it “bad” I call it “practical and a bit clever”. It may not be a efficient performer loaded with bold new technology, but all the components are sourced in a fairly frugal fashion (at least as frugal as aerospace can be), which makes up for its less than optimal mass fraction.

    Antares was developed on the cheap, and the cygnus flights alone pay for the vehicles development and operations for at least the next 5 years. All the while they offer a launch service to an underserved end of the market using a relatively open manifest and dedicated launch perks to try to attract customers that would otherwise be stuck as secondary payloads on bigger LV’s like falcon, airane, proton, and atlas. making any customer attracted in this fashion essentially gravy on top of thier cargo contract turkey dinner.

    So yeah good design does not always mean good mass fraction.

  • Antares was designed to fill a certain capability requirement in a way that it made maximum economic sense, especially regarding the number of outstanding flight per year vs fixed costs.

    Back when the whole concept was in the drawing board by Orbital (the Taurus II days), there were thoughts of incorporating a high energy second stage based on the RL-10 for the vehicle. I remember back then Dr. Antonio Elias (which btw has an incredible sense of humor, among a multitude of other superlatives) pushing this hard, both due to the obvious performance consequences as well as the low and easy to handle gross dry weight of the designed stack.

    Sadly, this did not came to be due to Orbitals’ lack of experience with liquid hydrogen, as well as overall cost considerations.

  • BarrieT

    It’s also worth remembering that Orbital had a late start as the replacement for Kistler, who couldn’t raise enough of their own money. I think the Frankenrocket design was a way of compressing the development timeline.

  • Saturn13

    !st flight. I do not think there will be any problems. At the news conference they said the test firing was really good. No mention of the unusual vibrations at a certain point. NASA said they will not linger there. There was not a full mission firing. I suppose the vibration will not change with lower fuel. This is a test flight and operational flight of a lot of new parts. I hope they turn down range as soon as they leave the pad and can’t fall on the pad as it did last time. If you want to see a real good turn like that, look up the all NASA views video of the Ares-1X test flight. It looks like the tail kicks out about 10′ and must have a degree from vertical. I will have my DVR going this time. Good luck to all.

  • ReSpaceAge

    RD-181 engine

    As Putin beats the drums of war………I’m just Amazed.

  • passinglurker

    I don’t think it matters. If things get too hot or even violent with russia who’s gonna have time to worry about commercial space flight any more?

  • Jeff2Space

    RL-10 engines certainly aren’t cheap. Add to that the other costs associated with cryogenic liquid hydrogen and the upper stage costs go up considerably.

  • Jeff2Space

    It is odd though that some politicians are making such a huge deal about ULA’s dependance on RD-180 but don’t seem to bat an eye at the RD-181. I’m betting it’s mostly due to the military/surveillance birds that fly on the Atlas V where Antares is just flying cargo to ISS.

  • Yep, pretty much. That was the justification for Orbital (combined with costs+experience needed to add LH to the GSE loop).