Nuclear Reactor Test Requirements Put DRACO Launch Plans On Hold
Posted: 30th January 2025
Nuclear Reactor Test Requirements Put DRACO Launch Plans On Hold |
Aviation Week Network
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Nuclear Reactor Test Requirements Put DRACO Launch Plans On Hold The
DARPA-NASA nuclear thermal propulsion project is extending its time
frame for an on-orbit demonstration.
Credit: Lockheed Martin
A vision to accelerate U.S. access to cislunar space and the wider
Solar System through a landmark demonstration of nuclear thermal
propulsion technology must wait.
The 2027 launch date for the Demonstration Rocket for Agile Cislunar
Operations (DRACO) is on indefinite hold. Since initiating the
program’s design phase two years ago, the DARPA-NASA management team
has encountered the challenges inherent in sending a nuclear reactor
into space for the first time in more than 60 years.
The demonstration rocket’s engine reactor remains in “pre-PDR”
phase
Safety requirements are critical factors in finalizing the engine’s
design The team, including BWX Technologies (BWXT) and Lockheed
Martin, hit snags in designing an engine that can be ground-tested
safely while adhering to the protocols necessary to test a nuclear
reactor, Matthew Sambora, one of two DRACO program managers in
DARPA’s Tactical Technology Office, tells Aviation Week.
“We’re bringing two things together—space mission assurance and
nuclear safety—and there’s a fair amount of complexity,”
he says.
DARPA and NASA awarded a contract to BWXT and Lockheed Martin in July
2023 for DRACO Phases 2 and 3. BWXT was in charge of designing and
building the reactor, manufacturing the fuel and delivering the
complete subsystem. Lockheed would integrate the reactor with the
engine and a demonstrator space vehicle ahead of on-orbit tests, then
scheduled for 2027.
That team is now focused primarily on developing and delivering the
DRACO engine and associated reactor, Sambora says. As such, “2027 is
not a date that we’re shooting for at this point,” he explains,
stressing that an eventual on-orbit demonstration remains a primary
goal of the program.
The engine would consist of a 1-m-long (3.2-ft.),
ultra-high-temperature, high-assay low-enriched uranium-fueled,
flow-through nuclear reactor. The fission reaction is harnessed to
generate heat to energize a helium gas propellant, which is exhausted
to produce thrust. A follow-on operational engine would replace
helium with more energetic liquid hydrogen fuel.
The DRACO team has not signed off on a design for BWXT’s reactor,
Sambora says. “We are considering ourselves still pre-completed PDR,”
he adds, referring to the preliminary design review. But he asserts
that DARPA and its NASA partners will get there and that DRACO’s
mission is not “undoable” but rather “difficult.”
While the reactor is at a “PDR level of maturity,” DARPA says it is
examining design refinements meant to improve ground processing
safety and enhance on-orbit data collection.
Lockheed Martin and BWXT plan to perform a cold flow test of the
reactor in 2025, Kevin Au, Lockheed Martin Space’s vice president of
lunar exploration campaigns, tells Aviation Week, expressing support
for DARPA’s approach to focus resources on engine development.
The U.S. has not launched a reactor since the 1960s, an era
euphemistically referred to as “the time before safety was invented,”
says Jim Shoemaker, DARPA’s second DRACO program manager. Scientists
in the Nuclear Engine for Rocket Vehicle Applications program
conducted six ground tests of radioactive reactors in open air
between 1964 and 1969, “which we could never get approved to do
today,” Shoemaker notes.
A DRACO ground test would need to capture plume exhaust fully to
ensure no radioactive materials are released to the environment, but
the U.S. does not possess this type of engine test capability, Ramon
Osorio, a spokesperson at NASA’s Marshall Space Flight Center in
Huntsville, Alabama, tells Aviation Week.
While “cost-effective” approaches are being explored for a
single-event, short-duration engine test comparable to what the DRACO
effort would require, Osorio says that “qualifying an operational
nuclear thermal propulsion engine for space transportation will
require a ground-test capability that accommodates full-duration
engine operations, with additional facility support to disassemble
the engine for an engineering assessment of the internal hardware
post-test.”
As it explores potential means of testing the engine, the DRACO team
is working to maximize ground-based component and subsystem testing
that can be done with existing capabilities, a subset of which will
take place at Marshall Space Flight Center, Osorio says.
Even after the demonstration, DRACO’s challenges will not be behind
it. Long-term storage of cryogenic hydrogen for the follow-on
propulsion system remains a key challenge for the scientific
community.
Meanwhile, DARPA released a request for information on Dec. 13
regarding ways the DRACO engine could be hosted more widely across a
range of space vehicles—for example, by building a nonproprietary
interface based on the current reactor design and development
program.
“As part of any program, it’s good to understand what’s available and
to be continually evaluating options and ways forward and adjusting
your thinking,” Sambora says.
At this point, Lockheed Martin’s role in the DRACO project is to
provide an engine and support DARPA and NASA in developing the safety
requirements and launch integration protocols along with ground
handling procedures, he explains, to integrate and launch a reactor
safely. “We’re not set into, at this point, any one way of getting
this demonstration done,” he says.
DRACO’s current spacecraft bus design is based on Lockheed Martin’s
Osiris-Rex spacecraft, which visited and collected samples from the
near-Earth asteroid Bennu over a seven-year mission that ended in
2023. “We have a strong baseline we can apply from that to DRACO,” Au
says.
Once a DRACO demonstration proves successful, it could take another
10-15 years before the technology is used on an operational basis,
says Shoemaker, who was the first program manager for DARPA’s Orbital
Express mission.
That project demonstrated satellite servicing activities in 2007,
such as rendezvous proximity operations, docking and fluid transfer.
In 2019, Northrop Grumman launched its Mission Extension Vehicle-1, a
commercial satellite designed to service aging satellites.
In addition to military access to cislunar space, NASA wants nuclear
thermal propulsion to enable new exploration missions, such as this
concept for a Mars Transfer Vehicle. Credit: NASA Concept Nuclear
propulsion is crucial to future military and civil space programs,
offering the potential to reduce trip times substantially and lower
the risks associated with space radiation, zero gravity, launch and
orbital assembly requirements. The U.S. Space Force needs it to allow
spacecraft to maneuver more nimbly on orbit, while NASA’s goal is to
support deep space exploration and transport humans to Mars.
For the first time since the collapse of the Soviet Union, the U.S.
and Europe are not alone in their pursuit of space nuclear
propulsion. Six years ago, China launched a program to develop a
“megawatt-class, ultra-small, liquid metal-cooled, space nuclear
reactor,” scientists reported in the April 2024 edition of the
Chinese Science academic journal. Component-level testing verified
the feasibility for an experimental prototype Chinese reactor, which
is based on a highly enriched uranium fuel, the report states.
The U.S. and Chinese programs share a common goal of unleashing space
travel at durations and speeds impossible with chemical- or
solar-based propulsion systems. The U.S. program also capitalizes on
newly gained bipartisan support for nuclear power. In his first term,
President-elect Donald Trump signed a policy document that
kick-started the Pentagon’s space nuclear reactor testing efforts.
The updated policy transfers authority for launching a nuclear
reactor into space from the White House to the Pentagon, easing the
political road to approval.
—With Steve Trimble in Washington
Editor’s note: This article has been updated to correct the length of
the nuclear reactor.