The case for kerolox
by Jeff Foust
|“This isn’t the first time that there have been articles about Russia cutting off RD-180 exports,” Aldrin said. “It’s happened before and it’s not something we worry about very much at all.”
However, NASA hitching rides on Soyuz spacecraft is not the only, or even most serious, example of American dependence on Russia space capabilities. Arguably a more fundamental reliance on Russia exists with the launch vehicle that is today the workhorse for US government civil and national security missions, the Atlas V. While built in Alabama by United Launch Alliance (ULA), its first stage is powered by an RD-180 engine built by a Russian company, NPO Energomash. That engine has had a perfect track record for the Atlas V, helping launch everything from classified military spacecraft to NASA probes, and is also the vehicle selected by two of the three currently-funded commercial crew vehicle developers.
That arrangement has worked well for more than a decade, but carries with it risk: if relations between the United States and Russia sour, Russia could elect to block exports of the RD-180 to the US. Such a move would not immediately stop Atlas V launches—ULA has a stockpile of RD-180s in the US—but it would force the company, and its primarily US government customers, to find alternative means of launching their payloads, be it switching to the Delta IV, Falcon 9, or other vehicles, assuming they are available and capable of carrying out those missions.
About a month and a half ago, with US-Russian relations in at least something of a rough patch, the specter of an RD-180 ban popped up again. The Russian news network Russia Today, quoting a report in the newspaper Izvestia, claimed that Russia’s Security Council was weighing a ban on RD-180 exports that would take effect in 2015. The rationale for the ban, according to the report, was that the engines were used for the launch of American military spacecraft, and that Russian space industry should be focused on supporting its own space efforts.
The report, though, also suggested that the proposed ban might have financial roots. The engines, sold by a joint venture of NPO Energomash and Pratt & Whitney called RD AMROSS, have a price tag of $11–15 million each, according to the Russia Today report, less than the cost to build them. By the late 2000s, the losses NPO Energomash incurred on RD-180s accounted for two-thirds of the company’s overall losses. (Blocking sales of the RD-180, though, could be more painful for the company, the article adds, since ULA is currently the only customer for those engines.)
Since that report, there’s been no public evidence that the Russian government is moving forward on any effort to block or otherwise curtail RD-180 exports. Those who have followed the Russian space program aren’t surprised with what appears to be another round of empty rhetoric.
“In the aerospace business, business has trumped politics” in Russia, said Andrew Aldrin, a ULA executive whose studies of the Russian space industry predate the collapse of the Soviet Union. Aldrin, speaking at a launch services panel session at the AIAA Space 2013 conference last month in San Diego, did not sound worried about the reports of a potential ban on RD-180 exports.
“This isn’t the first time that there have been articles about Russia cutting off RD-180 exports. There’s never been any perturbation in the process,” he said. “It’s happened before and it’s not something we worry about very much at all.” Should there be any such “perturbation” in the future, he added, ULA had a stockpile of RD-180 engines that would last the company for several years.
The threat—real or imagined—of a ban on RD-180 exports isn’t the only issue surrounding that engine in recent months. In June, Orbital Sciences Corporation filed suit against ULA, claiming ULA was preventing Orbital from buying RD-180s from RD AMROSS. Orbital is interested in the RD-180 as a potential long-term replacement for another Russian engine, the NK-33 (designated AJ26 after their purchase and refurbishment by Aerojet Rocketdyne), currently used on Orbital’s Antares rocket. The US Federal Trade Commission (FTC) also opened a probe into the RD AMROSS-ULA exclusivity deal earlier this year, an effort currently on hold because of the federal government shutdown.
|“The RD-180 is a magnificent engine, but the policy implications of depending on that are things that concern us,” said McCasland.
So why all the interest in the RD-180? Besides being commercially available (at least in theory) and relatively inexpensive, the RD-180 is also a high-performance engine. The RD-180 uses a technology called oxygen-rich, or ox-rich, staged combustion, while American rocket engines that use the same propellant combination of liquid oxygen and kerosene have traditionally used a gas generator to power the engine’s turbopumps. The gas generator approach is simpler, but doesn’t offer the same performance as ox-rich staged combustion. An Air Force Research Laboratory (AFRL) presentation from 2012 noted that ox-rich staged combustion “is a higher performance cycle, providing a smaller launch vehicle or an increase in delivered payload.”
AFRL is interested in this technology for a program called Hydrocarbon Boost to develop a new rocket engine that uses ox-rich staged combustion. The effort, scheduled to continue until fiscal year 2020, would result in an engine that generates 860,000 pounds-force (3.8 million newtons) of thrust—the same as the RD-180.
The former commander of AFRL said that performance goal was no coincidence. “We would like to prepare for new engines for the ELV [expendable launch vehicle] fleet,” said Neil McCasland, who left AFRL in mid-2013, during an AIAA Space 2013 panel session. He cited in particular AFRL’s work on the Hydrocarbon Boost program. “The RD-180 is a magnificent engine, but the policy implications of depending on that are things that concern us.”
That effort, though, is almost alone among US government efforts in “kerolox” engine development. Past programs funded by NASA, like the RS-84 by then-Rocketdyne and the TR-107 by Northrop Grumman, fell by the wayside when NASA’s Space Launch Initiative program gave way to the Vision for Space Exploration in the mid-2000s. Today, as part of an advanced booster development effort for the Space Launch System, Aerojet Rocketdyne and Dynetics are studying the feasibility of reviving the F-1 engine used on the Saturn V to power boosters on later iterations of the SLS, but such an engine would likely not fly until some time in the 2020s—if ever.
One executive thinks there’s not enough emphasis on kerolox engines, either as a replacement for the RD-180 or for other applications. “What development that’s going on in kerosene today is at a really low level,” said Jim Maser, vice president of corporate strategy and development at GenCorp, the parent company of Aerojet Rocketdyne, in a presentation Friday to the National Academies’ Aeronautics and Space Engineering Board (ASEB) in Washington. “I can’t see any real need for additional new hydrogen engine development as a priority for this country… From a priority standpoint, it’s not really placing our limited dollars in the right place.”
“I would argue that it’s obvious that, as a nation, we are falling behind the Russians and now, likely, even the Chinese in the development of kerosene-based boost propulsion,” he said, citing the development of kerolox engines for China’s next-generation Long March 5 family of rockets. “If we don’t undertake new development to preserve and extend the current base, we risk falling behind in a critical area that will be required in the future for national security space.”
Maser said that while the advanced booster work for SLS was a “great idea,” he was skeptical that NASA will be able to afford continued development of the technology under its current and projected budgets. He also cited SpaceX’s development of its Merlin 1D, another kerolox engine, but noted it was a small and “relatively low performance” engine compared to Russian engines. The Merlin 1D, which first flew on the Falcon 9 v1.1 inaugural launch last month, uses a gas generator technology like other domestic kerolox engines, with each engine generating about 670,000 newtons (150,000 pounds-force) of thrust, less than a fifth of the thrust of the RD-180. (SpaceX, though, has hinted that it is developing a much larger engine, but has not indicated how large the engine would be and when it would be ready.)
|Maser called for “an integrated strategy and roadmap for access to space for this country in the long term that applies to every agency in this country… In the absence of that, I think we’re just going to get starts and stops, cancellations, the same old thing.”
Asked by the ASEB about the possibility of manufacturing the RD-180 domestically, Maser sounded doubtful, although not about its technical feasibility. Under the original requirements of the Evolved Expendable Launch Vehicle (EELV) program in the 1990s, a vehicle that used a Russian engine like the RD-180 had to have the option of manufacturing the engine in the US. At that time, Maser noted, he was working for McDonnell Douglas (later acquired by Boeing) investigating the potential use of the RD-180 for what became the Delta IV, and “it became clear to me at the time that building it on a recurring basis in the United States looked relatively expensive.” He said that he had no doubt that, technically, the RD-180 could be built in the US, citing progress Pratt & Whitney made on building key components, but the funding for that work ended several years ago when the government eliminated the requirement for “co-production” of the RD-180.
Maser instead advocated for the development of a new kerolox engine, using ox-rich staged combustion, with a thrust of between half a million and a million pounds-force (2.2 to 4.4 million newtons.) Such an engine, he said, could be used alone or in combination for multiple vehicle architectures. That approach “can provide a very cost-effective and reliable solution for this country, because then what you get is a capability that can be used for different applications, and thus get the volume in the industrial base” that can drive down costs, he said.
Maser said that such an effort, though, would only be meaningful as part of a broader national space transportation strategy, “an integrated strategy and roadmap for access to space for this country in the long term that applies to every agency in this country, something that we can agree upon, create a roadmap around, and have some stability,” he explained. “In the absence of that, I think we’re just going to get starts and stops, cancellations, the same old thing.”
Another catalyst for the development of a domestic large kerolox engine, Maser suggested, would be the interruption in the supply of RD-180s, but, like Aldrin last month, he didn’t believe Russia would actually ban exports of that engine. Given the poor track record of developing, and sticking to, the kind of broad space transportation strategies Maser said is necessary, the US many be continuing to rely on the RD-180 for many essential missions long after American astronauts stop flying on Soyuz spacecraft.