Orbital Eying ATK Solid Propulsion System for Antares First Stage


A proposed merger between Orbital Sciences Corp. and the aerospace and defense divisions of ATK could yield a more powerful -- and politically palatable – Antares launch vehicle, according to company officials.

Orbital Chairman and CEO David Thompson says his company is considering an ATK proposal to develop a solid-rocket propulsion system to replace the modified Russian NK-33 engines that power the Antares rocket's Ukrainian-built first stage.

In an April 29 interview following the proposed merger announcement, Thompson said ATK's bid is one of three – including two offered by Russian suppliers – that Orbital is currently reviewing.

“ATK has made that proposal and it's attractive,” Thompson said. “We haven't made any final decisions on which way to go there, but with the recent geopolitical events and the progress ATK has made over the last few years in advancing large composite-case solid rocket motors, that alternative is looking more and more attractive.”

The proposed merger, which is expected to close this year, would see Dulles, Va.-based Orbital bring ATK's space propulsion work in house, increasing Orbital's control over its rocket manufacturing from 40-45% today to 80% under the combined entity.

ATK, which built the Space Shuttle Reusable Solid Rocket Motors, is developing much of the core-stage boost for NASA's new Space Launch System. The company also produces the Antares launcher's Castor-30B solid-rocket upper stage, as well as an optional Star 48BV solid-fueled third stage.

In addition to creating a more vertical manufacturing operation, choosing a U.S.-sourced booster could help Orbital avoid scrutiny from U.S. national security hawks eager to end America's reliance on Russian rocket technology.

A large solid rocket first stage would also boost Antares' current 5,000-kg lift capacity to low Earth orbit by “20-25%, depending on the orbit in question,” Thompson says.

The increase would give Antares a lift capacity comparable to the SpaceX Falcon 9 v1.1 for launching small payloads to geosynchronous orbit, and could potentially broaden Orbital's customer base beyond its $1.9-billion International Space Station cargo resupply contract with NASA to include the U.S. Defense Department.

“We've submitted to the Air Force our intention to on-ramp Antares in some configuration to its Evolved Expendable Launch Vehicle (EELV) program in the future,” Thompson said. “That is our aim over the next couple of years.”

Thompson said the company needs three years to develop a new Antares first stage, though a demonstration flight for the rocket might not be necessary.

“There may be ways in which the results of that sort of demonstration could be achieved short of a full-up demonstration, and that's one of the factors we still have to work our way through,” he said.

Discuss this Blog Entry 3

on May 1, 2014

I think you're improperly conflating LEO and GTO. Antares would require much more than a 20% first stage boost to put anything reasonable into GTO, super synchronous or otherwise.

The SpaceX Falcon 9 can do on the order of 12t to LEO, or around 3.5t to a super synchronous geostationary transfer orbit (SSGTO). The GTO number should be higher, but SpaceX's lack of a high-energy upper stage hurts them, as does insisting on reserving performance to land and reuse their first stage -- SpaceX's recently contracted SES launches show the F9 can put 5+ tonnes into SSGTO if they reserve nothing.

Orbital's Antares, on the other hand, can put around 5t into LEO -- not GTO, but LEO. Even boosting that 20% to 6t puts them to barely half the F9's LEO lift capacity. The ATK Castor 30XL upper stage Antares uses has no capability to put a payload into GTO; LEO is as far as it goes without a third stage, and Antares simply doesn't have enough lift -- even with a 20% boost -- for a third stage big enough to put a modern comsat into GTO. The small third stages Orbital offers are for boosting small sats to higher LEO or SSO orbits only.

Antares is quite simply a medium-class LEO/SSO launcher. It's NK-33s are very cool and I'll be sad to see them go, but Orbital had a different list of priorities than SpaceX when they each designed their rockets, and getting comsats into GTO wasn't on Orbital's list.

If Orbital had a high energy hydrogen/LOX upper stage that massed the same as the Castor 30XL, then they could put a decent sized comsat into GTO. I believe they had one on the drawing board back when Antares was called "Taurus II" -- but they instead opted for a cheap 'n cheerful, plug 'n play ATK solid which, to be fair, fit their ISS resupply and LEO objectives perfectly.

The Antares is an excellent rocket, and I'll be following news of any upgrades or changes with interest, but it'll take more than replacing its liquid first stage with a couple of big ATK solids to address all the markets that F9 competes in.

on May 2, 2014

You are right. While boosting Antares performance 20-25% means the rocket could carry around 6 tonnes to LEO, it would not be enough for Antares to compete with Falcon 9 v1.1 for anything more than small-satellite missions to GTO (see amended copy above).

That said, I disagree with the idea that Falcon 9 v1.1 can put 5+ tonnes in supersynch if they reserve nothing.

SES-9, a 5.3-tonne hybrid satellite built by Boeing, is designed to carry 81 Ku-band transponders (36 MHz). But rather than taking it to SSGTO, SES-9 will be dropped in a subsynchronous orbit, where it will begin a three- to four-month journey to its final orbital position at 108.2 deg. east in geosynchronous orbit.

In this business, that is a long time. But the customer, SES, says the price of the launch vehicle is so low that it is worth the wait.

The 5.3-tonne SES-10, on the other hand, will not require such a lengthy delay in reaching its operating orbit. That's because Airbus Defence and Space is building it to carry additional chemical propellant that will be needed to raise its orbit. Note that the extra fuel is a trade for performance: the satellite will carry just 50 Ku-band transponders (36 MHz).

In an interview with Elon Musk earlier this year, the SpaceX CEO and chief designer put Falcon 9 v1.1 in the light class for launching satellites to SSGTO, assuming a weight penalty for the reusable first stage.

"Where I basically see this netting out is Falcon 9 will do satellites to roughly up to 3.5 tonnes with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages," he told me in March.

on May 3, 2014

I appreciate the reply, even if it reads like you copy and pasted most of it from other articles. ;-)

I'm afraid, however, that if you amended the copy then I can't see it -- I have the same objection with the text as I did previously and would proffer the same argument. The Antares and Falcon 9 are different classes of launcher, and to casually conflate Antares' abilities with Falcon 9's is improper.

Put simply, if as you say Falcon 9 is a "small payload" GTO launcher, then you should use a different adjective to describe Antares' GTO capabilities.

Orbital doesn't list an official capacity to GTO in its Antares User's Guide, which seems telling to start with, but do offer other official figures. GTO is around 700m/s shy of escape velocity or C3=0, and the guide's C3=0 chart shows that an Antares model 132 can put around 1.5t there, pretty much at the model's limit. Cross referencing against the subsequent 185km perigee chart, extending the performance line out beyond the 40,000km apogee limit shown on the axis to the height of an SSGTO apogee roughly agrees with the C3=-0.7km/s figure.

Even adding on a few hundred kilo boost from the proposed first stage change, the Falcon 9 in its reusable mode* can do about twice that, and SpaceX's official figure for GTO payload is 4.85t**, or three times it. Doubled (or tripled!) capacity is hardly insignificant, so if the Falcon 9 only does "small" GTO satellites, then Antares should be described as lifting something like "tiny" ones. Conflating the two is like conflating Falcon 9's ~13t LEO capacity (or ~16t, according to NASA's NLS performance charts, presumably fully expendable) with the ~28t the Delta IV Heavy can do.

Should Orbital want to compete on the same breadth of field as the Falcon 9 -- on the low end of the EELV scale, admittedly, but EELV-class nonetheless -- then Orbital needs to either design a bigger brother to Antares, or upgrade Antares' upper stage to hydrogen. Given that they just brought ATK in-house, that ATK's specialty is solids and not turbopumps, and that they'd obviously get a serious discount on the ATK catalog pricing that Orbital paid previously, I know which I'd bet on. Perhaps they could use a couple ATK solid stages to replace the liquid first stage, and then add smaller ATK solid boosters to increase its lift?

Even without the issues of NK-33 availability, Orbital will need to make changes, as NASA's CRS2 mass-per-lift requirements at a minimum (14t over 5 flights) exceeds even the yet-to-fly enhanced Cygnus' capabilities. SpaceX, on the other hand, has the opposite problem. F9 can lift the mass, but with only 10 m^3 of pressurized space, Dragon can't hold the minimum volume (55 m^3 over 5 flights).

It'll be interesting to see how it all plays out.

* How cool is it that we're discussing a rocket with both an expendable and reusable mode? :-)

** While I think it's not hard to imagine that SpaceX can cut reserve margins to the bone and increase this figure by 150kg to reach my 5t+ claim, the fact is that only SpaceX knows exactly how much F9 can put into SSGTO. 5.3t is too much since, as you say, the SES sats are going sub-supersyncrhonous, but 5.01t may not be. Regardless, "around 5t" would have been more defensible than "5t+", and I should have used it.

I was going to write some speculation (or is that wishful thinking? ;-) ) on where F9's performance will end up after sub-cooling the propellant, increasing is density to cram more tons of fuel into the tanks, and stepping up Merlin 1D's performance to use the 15% additional thrust that Elon has said it could do, but when I did a quick search for details on densification, the first result was your article mentioning it.

Apparently you write cool things and I should be more actively following your blog, not just finding the occasional link and wandering in. :-)

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