Launch Abort System (LAS) hardware for the Exploration Flight Test -1 (EFT-1) mission has arrived at the Kennedy Space Center (KSC) for integration on the Orion that will be launched on a Delta IV-Heavy next Summer. ATK’s inert motor will be used to simulate the same weight, structure and aerodynamics of the live motor configuration that will ride on the Space Launch System (SLS).
The launch abort motor is more than 17 feet tall, measures three feet in diameter, and includes turn-flow rocket manifold technology. It was successfully ground-tested in 2008, before enjoying a flight test at White Sands in New Mexico, during Orion’s Pad Abort (PA-1) test in 2010.
The LAS will conduct two further flight tests, the first during the uncrewed Exploration Mission -1 (EM-1) in 2017, prior to a High Altitude Abort test that will allow LAS to become a required safety element on the crewed Exploration Mission -2 (EM-2).
The LAS’ key role is to safely pull the Orion crew module away from the launch vehicle in the event of an emergency on the launch pad or during the initial ascent of an SLS mission.
“Our launch abort motor is critical to ensuring safety, allowing for a greater reduction in risks for crewed flights,” noted Charlie Precourt, ATK vice president and general manager of the Space Launch Division.
“ATK is proud to be a part of the Orion EFT-1 team. This is an important milestone for America’s new human exploration program, which includes Orion and the Space Launch System, with a heavy-lift capability to take crew and cargo on missions to the moon, asteroids and eventually Mars.”
The LAS for EFT-1 was actually manufactured back in 2008 as an inert pathfinder. It was then modified at ATK’s Bacchus, Promontory, and Clearfield, Utah, facilities to meet the needs of the test flight involving Orion riding on a United Launch Alliance (ULA) Delta IV-H.
The hardware has also been instrumented, allowing it to collect environmental and flight data during the test launch.
The EFT-1 LAS design reaches back to decisions made via the 2007 trade of several LAS concepts, namely the Multiple External (x4) Service Module (SM) Abort Motor concept, the Crew Module Strap On Motors (x4) concept, and the In-Line Tandem Tractor (Tower) concept – the latter becoming the baselined design for Ares 1/Orion.
The study (acquired by L2) had one major parameter, citing the preferred design should ensure the risk of losing the crew in an abort scenario would be no greater than 1 in 10.
The winning concept – the Tandem Tractor (Tower) LAS design – comprised of a Nose Cone, Attitude Control Motor (Eight Nozzles), Canard Section (Stowed Configuration), Jettison Motor (Four Aft, Scarfed Nozzles), Interstage, Abort Motor (Four Exposed, Reverse Flow Nozzles), Adapter Cone, and Boost Protective Cover (BPC).
The primary role of such a system is to save the crew during any one of three abort scenarios.
The first scenario involves an emergency caused by a failing vehicle whilst still on the launch pad. If the crew have no time to evacuate the vehicle, the LAS would fire, lofting Orion free to a safe distance, before parachutes are deployed for a landing in the Atlantic ocean – within a 3,450 foot radius due east of the launch pad.
The second scenario is noted as “mid altitude abort” – up to 150,000 ft during the ride uphill – involving the LAS firing the Orion safely away from the failing vehicle, sending the spacecraft to a point where drogue chute deployment can take place.
The final stage of an LAS-assisted abort is at an altitude of between 150,000 ft and 300,000 ft – the latter being the point the LAS would be jettisoned on a nominal flight. After being pulled away from the launch vehicle, Orion would revert to a flight profile similar to that used during the end of a normal mission.
Interestingly, one idea that was considered during the Constellation Program (CxP) efforts included the concept of using the LAS even after a successful launch through first stage flight. This related to Ares 1’s mass to orbit ability – or lack thereof – with the LAS firing to provide an extra kick uphill – not unlike the Shuttle’s use of its OMS engines during launch. This idea was problematic.
“LAS Abort Impulse used for Ascent Assist: Theoretically can increase mass to orbit by 1000 lb. However, additional tension loading on the Command Module requires additional structure that leads to overall decrease in mass to orbit,” noted an extensive NASA presentation (acquired by L2 – Link to Document).
However, engineers responded by evaluating the use of nozzle inserts in the LAS motors, which would have reduced the thrust and aided the negative structural loadings on the vehicle – mitigating the concerns of Command Module (CM) mass penalties.
“An Alternate Option Using Nozzle Inserts: Reduces Abort Motor Thrust, Increases burn time. Relieves Command Module Compressive load – no tension loads. Increases the Payload Mass-to-Orbit by ~650 lb,” added the presentation.
This option weakened as evaluations progressed, pointing to only a 400lb mass increase. There are no plans for this concept now Orion is hitching rides with the superior performance of the SLS.
While abort motors on the Service Module lost out during the trade studies, a new concept came forward called the Max Abort Launch System – or MLAS (named after Maxime (Max) Faget).
Although it was never publicly admitted, this system was often mentioned by sources as a potential boost to advocates of cancelling Ares 1 for a human rating the Ares V, as the Constellation Program (CxP) began to falter. Ironically, SLS is not too dissimilar to a human-rated Ares V.
MLAS also had the backing of then-NASA administrator Mike Griffin, not least because MLAS was an evolution of two of the original LAS concepts studied by Constellation, one of which made the LAS trade study in 2007 via a rather amusing hand-drawn sketch, a drawing created just one year previously.
The MLAS concept combined the BPC of the service module, mounted to the escape system, with the command module sporting mounted motors, in turn reducing the overall height of the vehicle – something desired by the Ares V HR advocates, who were concerned about the ability roll out the vehicle – with a LAS tower – under the height restrictions of the Vehicle Assembly Building (VAB) doors.
The MLAS utilized a ‘bullet’ boost protection cover over the capsule, housing four Mk 70 Terrier solid motors separation motors. Two orientation parachutes were attached to the top of the fairing to re-orient the vehicle, with the blunt heat shield used to aid fairing separation.
This design resulted in the aborting vehicle re-orienting immediately after abort motor cut off during a pad abort, before flying with its nose “into the wind” on a mid-altitude abort. The orientation parachutes would then activate quickly before the fairing separation occurred.
In the event of a high altitude abort, the fairing would immediately separate, in order to allow the Command Module Reaction Control System (RCS) to stabilize the vehicle for entry.
The design of MLAS changed several times during its development, gaining fins for stability during later cycles, becoming more in line with another hand drawn sketch.
This time the artist was former Constellation head Scott “Doc” Horowitz – as seen in the second of two MLAS presentations acquired by L2 (Link to Presentations) – over a year after Mr Griffin’s conceptual design.
The final version of the MLAS flight test vehicle weighed in at massive 45,000 lbs and was over 33 feet tall. This design actually got to fly for real, after being shipped to Wallops for its one and only hop off the ground.
The test began seven seconds after burnout of its specially attached solid motors, as the vehicle rose into the Virginia morning sky at 6:25am local time on July 8, 2009.
Video of the launch portrayed a perfect test, as the vehicle rose on a stable flight path, before reorientation and further stabilization was initiated.
This was soon followed by crew module simulator separation from the MLAS fairing, along with parachute recovery.
Other tests were planned for MLAS, including a high altitude abort that would have involved the fairing being released immediately after abort was called, in order to allow the Command Module Reaction Control System (RCS) to stabilize the vehicle for entry.
However, the program was put on the backburner, as the Constellation Program was cancelled.
While it is highly unlikely NASA will change paths with the baseline design that will launch with Orion, SpaceX are working on an arguably superior system for use with their Dragon spacecraft, hardware that is not only fully integrated into the body of the spacecraft, but one that also holds future uses that aren’t even related to launch abort.
The first major difference relates to the traditional use of solid propellant, mainly because of the speed it can ignite and reach full thrust – something highly desirable when moving human lives away from a failing rocket.
However, Dragon sports a series of eight liquid SuperDraco engines, built into the side walls of the Dragon spacecraft, capable of producing up to 120,000 pounds of axial thrust to drive the Dragon away from its failing launch vehicle.
SpaceX’s SuperDraco liquid motor showed it’s no slouch when compared to a solid, achieving full thrust within approximately 100 milliseconds of the ignition command during test firings at the SpaceX’s Rocket Development Facility in McGregor, Texas.
Advantages of the SuperDraco liquid thruster include how the engine can be put through a series of throttling ranges, in turn allowing for redundancy, with SpaceX claiming they could lose one of the eight abort engines and still recover the vehicle and crew successfully.
The engines can also be restarted multiple times.
Another advantage is the fact it isn’t a tower design, hardware that requires jettison shortly after first stage flight.
Because the system is integrated into the Dragon itself, the spacecraft can technically abort within much longer periods than the tower version. With Dragon returning with the engines on board, they can also be reused on future launches.
There is also a large amount of commonality between the 18 maneuvering engines built into Dragon and the SuperDraco LAS engines – bar the fact the SuperDraco engines would burn through propellant 200 times faster.
The biggest long-term advantage of this system is related to the potential use of the engines to land Dragon back on land propulsively, as seen via SpaceX’s Reusable Falcon 9 concept, which returns all of the launch vehicle and spacecraft hardware to the launch site for reuse.
Parachutes will still be onboard the Dragon for a contingency event resulting in problems with the SuperDracos, allowing the spacecraft to land on water, as it is currently designed to do.
However, Earth isn’t the only landing destination for Dragon, with SpaceX holding ambitions of landing on the Moon and more notably Mars.
Nicknamed “Red Dragon” – SpaceX have made no secret about their ambitions to head to Mars, publishing a graphic of their spacecraft touching down on the Red Planet.
Such a mission is deep into the future, although Elon Musk, SpaceX CEO and Chief Technology Officer, has said he is highly driven to make Mars missions a reality, not least – per an interview with the BBC – because he wants to be able to go to the Red Planet himself, before he gets “too old”.
NASA’s own Mars plans are a mix of old mission outlines and revamped videos, but they also have propulsive landing ambitions – in tandem with large parachutes – with the latest conceptual Mars mission videos showing massive cargo landers and crew habitats touching down under large amounts of propulsive power.
This technology is likely to be refined over the years to come, although the success of Curioisty’s propulsive landing on Mars has shown NASA engineers are on the right track.
(Images via NASA, SpaceX, and L2 content)
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