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Proposed Liberty launch vehicle on Mobile Launch Platform at KSC LC-39B
On May 9, 2012, ATK and Astrium announced that they were offering their Liberty launch vehicle as part of a complete commercial crew transportation system, including a spacecraft, abort system, launch vehicle, and ground and mission operations, in a bid for NASA's Commercial Crew launch program. For the first time Lockheed Martin was introduced as a major Liberty subcontractor, filling out a formidible team.
In this article, Space Launch Report reviews Liberty's program history and analyzes its design.
On February 8, 2011, one year and one week after U.S. President Obama cancelled NASA's Ares 1 launch vehicle and its Orion crew carrying spacecraft, ATK and Astrium announced their Liberty launch vehicle proposal for NASA's Commercial Crew Development (CCDev) project, a plan that would combine the cancelled Ares 1 first stage with an Ariane 5 core stage to create a new crew launch vehicle.
ATK would supply the five-segment solid rocket motor first stage, derived from the Space Launch System (SLS) booster. Astrium would provide Liberty's second stage, which would be a modified Ariane 5 EPC core powered by a Snecma Vulcain 2 engine. Both stages, the proposal noted, had been designed from the outset to launch people. Liberty would be able to boost a 20.185 tonne payload to the 51.6 degree inclination International Space Station (ISS) orbit.
The ATK/Astrium team noted that Liberty could launch any crew vehicle then being contemplated for CCDev. The team planned an initial flight by the end of 2013, a second test flight in 2014, and operational capability in 2015. Other Liberty team members included United Space Alliance (USA) for launch vehicle integration and ground operations support, and L-3 Communications for first stage avionics.
On April 18, 2011, NASA awarded about $270 million to four companies for the second round of CCDev. Funded winners included Blue Origin, Sierra Nevada Corporation, SpaceX, and Boeing. Liberty was among the proposals that were selected, but not funded, under a Space Act Agreement (SAA). ATK and Astrium continued to work on Liberty under this arrangement, self-funding their efforts while sharing their findings with NASA.
In September, 2011, ATK and Astrium announced that they
would submit a proposal for CCDev-3, the next step in NASA's Commercial Crew program.
Liberty with MLAS and Liberty Spacecraft
A November, 2011 ATK presentation provided more details about the Liberty rocket. It described three potential Liberty variants. Liberty L1 would use a recoverable first stage, adhering to Ares 1 plans. Liberty L2 would delete first stage recovery to gain more performance and to cut operating costs. Liberty L3 would replace the steel segment case first stage with an advanced booster that would also be developed for NASA's Space Launch System. The advanced booster might use composite segment casings, or it might use steel casings overwrapped in composites.
In each case, an "A" variant would be used to launch ISS crew, a "B" version would launch ISS cargo, and a "C" model would launch government satellites. Capability was now listed as 19.278 tonnes to LEO/ISS for crew missions and 19.051 tonnes to LEO/ISS for cargo missions. For the first time, a three-stage capability was suggested that could boost 8.845 tonnes to geosynchronous transfer orbit (GTO), 7.938 tonnes toward the Moon, or 6.804 tonnes to escape velocity. The third stage was not described, but performance seemed consistent with the planned Ariane 5 ECB restartable Vinci powered ESC-B stage.
The presentation showed that the Ariane 5 Vehicle
Equipment Bay (VEB) would be adapted to provide guidance and control of Liberty and that
the EPC stage would have structural modifications to allow it to fly atop Liberty.
Initial test flights were slated to begin in 2014, with crew flights tests beginning in
2015. ATK/Astrium presented Liberty's initial systems design to NASA's Commercial
Crew Office at Kennedy Space Center during January, 2012. By May, 2012, Liberty had
completed four of its five SAA milestones. The final major milestone would be a structural
test of the second stage planned to be performed at Astrium during June, 2012.
Enter Lockheed Martin
On May 9, 2012, ATK and Astrium made their Liberty spacecraft announcement. The team's bid was for the third round of Commercial Crew, which was expected to be awarded during August, 2012.
Liberty's spacecraft would be based on ATK's composite crew module, which the company built at its Iuka, Mississippi plant for NASA Langley between 2007 and 2010 in a test of an alternative for Orion's Aluminum-Lithium pressure shell. Lockheed Martin would outfit the module at its KSC Orion/MPCV facility, using Orion subsystems. Lockheed Martin would also provide a Service Module (SM) derived from Orion's SM. In appearance, the Liberty spacecraft looked like an "Orion Lite", shorn of solar panels and other systems. An ATK Max Launch Abort System (MLAS), another system test flown during the Constellation Program, would provide crew escape in the event of ascent failure.
Liberty test flights were expected to begin in 2014, with a crewed test mission in late 2015. Crewed missions to ISS would begin in 2016. Launches would take place from Kennedy Space Center using renovated Shuttle launch pad LC 39B. ATK reiterated the original 20.185 tonne payload capacity, noted that Liberty would carry seven astronauts, and that the price-per-seat would be less than the price NASA was paying Russia for flights on Soyuz.
Additional subcontractors included Safran/Snecma
(Vulcain 2 engine), Safran/Labinal (second stage wiring), L-3 Communications (first stage,
abort and telemetry system avionics and second stage telemetry and abort system
integration), and Moog Inc. (thrust vector and propulsion control).
A two-stage Liberty Launch Vehicle would consist of a five segment booster first stage, an interstage, an EPC second stage, a VEB avionics unit, and a payload.
Five Segment Booster, or "RSRB-V", originally developed for NASA's cancelled Ares 1 crew launch vehicle, was subsequently adopted for the Agency's Space Launch System. It would be the world's most powerful rocket motor, able to produce 1,588 tonnes (3.5 million pounds) of liftoff thrust. It would weigh about 732.55 tonnes at liftoff and burn 627.2 tonnes of propellant during its 126 second burn.
During Constellation, ATK performed booster recovery pilot parachute testing as early as 2006. It cast its first inert segments by mid 2008 and, in November 2008, began casting its first live segments. By the end of 2011, ATK had performed three successful five segment booster tests at its Utah test site. The tests took place on September 10, 2009 (DM-1), August 31, 2010 (DM-2), and September 8, 2011 (DM-3). A precursor test of a five segment motor, assembled using an extra segment from a Shuttle four-segment motor, occurred on October 23, 2003 (ETM-3).
The "Ares I-X" suborbital test flight, successfully performed on October 28, 2009 from KSC LC 39B, used an existing four-segment RSRB fitted with a dummy fifth segment. This first stage was topped by dummy interstage, second stage, and Orion boilerplate hardware. A live roll control system in the interstage was active during the flight. The test validated the basic early ascent flight control of the in-line SRB configuration that would also be used by Liberty.
Athough ATK performed recovery system tests for Ares 1 five segment motor, and recovered the Ares I-X booster, no plans were being made to recover either the SLS or, now, the Liberty motors, eliminating the previously described "L1" variant.
Liberty would use a
modified version of the Ares 1 interstage. The composite interstage, which weighed
4.16 tonnes for Ares 1, would flare out from the 3.71 meter first stage diameter to the
5.4 meter EPC second stage diameter, 0.1 meter slimmer than the Ares 1 Upper Stage
diameter. The interstage, which contains a section called the "frustum" on
Ares 1, would house roll thrusters. Deletion of first stage recovery would make the
interstage lighter by removing recovery parachutes, tumble thrusters, and an aerodynamic
fairing. The first stage would stand about 53 meters tall to the top of the frustum.
EPC Stage at Kourou
Liberty's second stage would consist of a modified Ariane 5 cryogenic main stage, named Etage Principal Cryotechnique (EPC) by its French builders. EPC is 30.5 m high and 5.4 m in diameter. It consists of a forward liquid oxygen tank and an aft liquid hydrogen tank. Both tanks are aluminum shells that must remained pressurized when empty to maintain their shape. The LOX tank walls are 4.7 mm thick while the LH2 tank walls are only 1.3 mm thick. The forward tank can hold 150 tonnes of LOX. The aft tank can old 25 tonnes of LH2. When flown on Ariane 5, EPC weighs about 14 tonnes empty and about 189 tonnes when loaded with propellant.
A single Vulcain 2 engine powers the stage, providing 136 tonnes of thrust for about 540 seconds. It also provides roll control during the main propulsion phase. At shut down, EPC separates from Ariane's upper stage and reenters.
On Ariane 5, the EPC is topped by a forward skirt named JAVE ("Jupe AVant Equipée") that transmits thrust from the two solid boosters to the core vehicle. This structure will not be needed on Liberty.
Araine 5 launchers are topped by a Vehicle Equipment Bay (VEB) that houses guidance and control systems, along with sets of hydrazine fueled roll and pitch thrusters. The VEB, which is usually positioned atop the Ariane 5 second stage, is 5.4 meters in diameter, is 1.56 meters tall, and weighs 1.9 tonnes.
EPC will be modified for use on Liberty. The tank walls will have to be strengthened, but some or all of the added mass would likely be offset by the elimination of the JAVE. Vulcain 2 would have to perform an air start, but since it is a gas generator engine modifications are expected to be managable. Snecma and Astrium have already been working on air start designs. Ground test firings of an air-start Vulcain 2 would occur in mid 2013 if Liberty won a NASA contract.
One advantage of the EPC design is the forward positioning of the LOX tank, which serves as a damping mechanism for first stage thrust oscillation. The Ares 1 Upper Stage would have positioned the less dense LH2 fuel tank on top of the denser, heavier LOX tank, a configuration that was more difficult to detune from the first stage oscillation frequency.
EPC would likely be loaded with less propellant for Liberty than for Ariane. In order for the second stage to start with at least as much thrust to weight ratio as the Ares 1 Upper Stage, the Liberty second stage, VEB and payload would have to weigh less than about 180 tonnes at Vulcain 2 ignition. That implies a 144 tonne maximum propellant load, which is about 31 tonnes or 17.66 % less than an Ariane 5 EPC - a few tonnes more than the planned Ares 1 Upper Stage propellant load. Vulcain 2 would only burn for 445 seconds with that load. The EPC stage could presumably be shortened to accomodate the smaller load and to reduce dry mass, but no details have been provided about any such changes and simplified analysis indicates that a full-size EPC should be able to achieve the stated payload objective.
Liberty would lift off from KSC LC 39B, from either a new or a modified mobile launch platform. After its 126 second burn, the first stage would separate by having booster separation motors fire to backed the stage away from the upper stage and/or interstage. Ares 1 used a dual plane separation method, with the interstage dropping from the second stage shortly after first stage separation. ATK has not yet said if Liberty will use the same method.
After staging, the second stage Vulcain 2 would ignite
to continue the ascent. The MLAS system would jettison about one minute after
staging. The target insertion orbit would be reached about 9.5 minutes after
liftoff. Although Liberty officials have not described target orbit parameters, it
seems likely that the second stage and payload would, like Ares 1 or the Shuttle ET and
Orbiter, separate at slightly suborbital velocity. This would allow the second stage
to be safely dropped into the Indian or Pacific Ocean while allowing the Liberty
spacecraft to perform a small burn to enter orbit.
Ares IX Stacking and Launch at Kennedy Space Center
Compared to its Commercial Crew competitors, Liberty would lift roughly twice as much payload, inferring twice as much launch cost. ATK/Astrium could offset this cost by offering simultaneous cargo hauling along with the crew spacecraft. This two-in-one approach could reduce total launches. It could also allow crew/cargo interactions and training that were similar to Shuttle operations. The Liberty spacecraft might be able to offer more delta-v than its competitors so that it could provide more ISS boost or propellant transfer. Liberty could launch heavier and more capable cargo spacecraft, similar to ATV or HTV, than its competitors.
The use of Orion systems could simplify crew training and qualification. It might also cut spacecraft costs. Plans called for up to four Liberty spacecraft capsules to be built, with each reused for up to ten flights.
Finally, unlike its competitors, the Liberty team has
focused on Kennedy Space Center, home of all U.S. crewed launches since 1968 and site of
NASA's Commercial Crew Office which will award the contracts. Of all Commercial Crew
alternatives, only Liberty would use Launch Complex 39, including the VAB and LCC.
The Liberty spacecraft would be assembled at KSC's Operations & Checkout
Building. Liberty would use SRB transport, storage, and assembly infrastruture and
personnel. Its docks and waterways would accomodate the EPC stage delivery from
France, a journey that would actually be shorter than the normal route to Kourou for
Shuttle Derived Launch Vehicles - A Solution for Space Access, James A. Furfaro and Dennis G. Johnson, ATK Thiokol Inc., 2005.
Fragola, J.R., Putney, B., Minarick, J., Baum, J.D., Franzini, B., Orlando, S., Lohner, R., Mestreau, E.,and Ferricane, R., Reliability and Crew Safety Assessment for Solid Rocket Booster / J-2S Based Launch Vehicle, Science Applications International Corp., SAICNY05-04-1, 2005.
NASA's Exploration Systems Architecture Study (ESAS), Final Report, NASA-TM-2005-214062, November 2005.
Upper Stage Request for Information, NASA's Exploration Launch Office, March 20, 2006.
Ares Project Status, Presentation by Steve Cook, Director Exploration Launch, NASA, Second AIAA Space Exploration Conference, December 2006.
Liberty Launch Vehicle Press Conferences, ATK/Astrium, 2011-2012.