«ABSTRACT On August 9, 2012 the Morpheus 1.5A vehicle crashed shortly after lift off from the Kennedy Space Center. The loss was limited to the ...»
Morpheus 1.5A Lander Failure Investigation Results
Jennifer L. Devolites1, Jon B. Olansen, PhD2, and Stephen R. Munday3
NASA Johnson Space Center, Houston, TX 77546
On August 9, 2012 the Morpheus 1.5A vehicle crashed shortly after lift off from the Kennedy
Space Center. The loss was limited to the vehicle itself which was pre-declared to be a test failure and not a mishap. The Morpheus project is demonstrating advanced technologies for in space and planetary surface vehicles including: autonomous flight control, landing site hazard identification and safe site selection, relative surface and hazard navigation, precision landing, modular reusable flight software, and high performance, non-toxic, cryogenic liquid Oxygen and liquid Methane integrated main engine and attitude control propulsion system. A comprehensive failure investigation isolated the fault to the Inertial Measurement Unit (IMU) data path to the flight computer. Several improvements have been identified and implemented for the 1.5B and 1.5C vehicles.
1. INTRODUCTION NASA’s strategic goal of extending human activities across the solar system requires an integrated architecture to conduct human space exploration missions beyond low earth orbit (LEO). This architecture must include advanced, robust in-space transit and landing vehicles capable of supporting a variety of lunar, asteroid and planetary missions; automated hazard detection and avoidance technologies that reduce risk to crews, landers and precursor robotic payloads; and in-situ resource utilization (ISRU) to support crews during extended stays on extraterrestrial surfaces and provide for their safe return to earth. The Advanced Exploration Systems (AES) Program portfolio within NASA includes several fast-paced, milestone-driven projects that are developing these necessary capabilities and, when integrated with subsystem technologies developed by Science Mission Directorate (SMD) investments, can form the basis for a lander development project. Specifically, the Morpheus, Autonomous Landing & Hazard Avoidance Technology (ALHAT), and Regolith & Environment Science & Oxygen & Lunar Volatiles Extraction (RESOLVE) projects provide the technological foundation for lunar surface demonstration missions later in this decade, and for key components of the greater exploration architecture required to move humans beyond LEO.
The Morpheus Project provides an integrated vertical test bed (VTB) platform for advancing multiple subsystem technologies. While technologies offer promise, capabilities offer potential solutions for future human exploration beyond LEO. Morpheus provides a bridge for evolving these technologies into capable systems that can be demonstrated and tested.
This paper describes the activities of the Morpheus Project, ongoing integration with ALHAT through FY12-13, and expectations for the future, with the goal of developing and demonstrating these human Morpheus Systems Engineering & Integration Manager, Mail Stop EA34 Morpheus Project Manager, Mail Stop EA32, AIAA Senior Member Morpheus Deputy Project Manager, Mail Stop EA32 American Institute of Aeronautics and Astronautics: SPACE 2013 Figure 1 - Morpheus 'Alpha' Vehicle is prepared for testing at Kennedy Space Center in August 2012.
spaceflight capabilities with robotic missions to the lunar surface.
The Morpheus Project provides a liquid oxygen (LOX) / liquid methane (LCH4) propelled vehicle that, when leveraging subsystem designs developed by other VTBs such as the Marshall Space Flight Center’s (MSFC) Mighty Eagle Lander, may be developed into reusable platforms for in-space transit and/or planetary landing for multiple missions and payload capacities. Such platforms could directly support robotic missions and would eventually mature into capabilities advantageous for manned missions.
The LOX/methane propulsion system is one of two key technologies that Morpheus is designed to integrate and demonstrate. The Morpheus LOX/methane propulsion system can provide a specific impulse during space flight of up to 321 seconds; it is clean-burning, non-toxic, and cryogenic, but space-storable. Additionally, for future space missions the lox and/or methane could be produced in situ on planetary surfaces, and the oxygen is compatible onboard with life support systems and power generation. These attributes make LOX/methane an attractive propulsion technology for a lander of this scale.
ALHAT, the primary Morpheus payload, provides the second key technology: autonomous landing and hazard avoidance. When landing autonomously on any planetary or other surface, the vehicle must be able to identify a safe landing site that is free of large boulders, rocks, craters, or highly sloping surfaces. Morpheus is designed to carry ALHAT sensors and software supporting tests that will demonstrate an integrated vehicle capability to perform these tasks.
2. SYSTEM DESCRIPTIONThe VTB system elements include the flight test vehicle, ground systems, and operations.
A. Vehicle Morpheus design and development began in June 2010, primarily by an in-house team at NASA’s Johnson Space Center. The current iteration is the Morpheus ‘1.5 Bravo’ vehicle, and system description references the current vehicle build.
Morpheus is a “quad” lander design with four tanks and a single engine. The primary structure consists of welded aluminum box beams, machined parts, and aluminum plate. The landing struts have honeycomb crush pads in the feet to attenuate landing loads. The propellant tanks are made of welded aluminum hemispheres. The avionics and GN&C components are located on a plate that spans the top deck of the primary structure.
The propulsion system uses an impinging element-type engine design, with liquid oxygen and methane as the propellants. The engine is film-cooled and operates as a blow-down system producing up to 5000 lbf of thrust. Two orthogonal electromechanical actuators (EMAs) gimbal the engine to provide thrust vector control of lateral translation and pitch and yaw attitudes. LOX/LCH4 pencil thrusters fed from the same propellant tanks provide roll control with a redundant set of helium jets that use the pressurized helium in the propellant tanks onboard as a backup system. Varying the engine throttle setting provides vertical control of ascent and descent rates.
The avionics and power subsystems include the flight computer, data recording, instrumentation, communications, cameras, and batteries. The flight computer is an AITech S900 CompactPCI board with a PowerPC 750 processor. Up to 16 GB of data can be stored on board. Data buses include RS-232, RS-422, Ethernet, and MIL-STD-1553. Multiple channels of analog and digital inputs are used for both operational and developmental flight instrumentation, including temperature sensors, pressure transducers, tri-axial accelerometers, and strain gauges. Wireless communications between ground operators and the vehicle use a spread spectrum frequency band.
Two on-board cameras provide views of the engine firing during testing. Eight lithium polymer batteries provide vehicle power.
The GN&C sensor suite includes a Javad Global Positioning System (GPS) receiver, an International Space Station (ISS) version of Honeywell’s Space Integrated GPS/INS (SIGI), a Systron Donner SDI500 Inertial Measurement Unit (IMU), and an Acuity laser altimeter. The vehicle is able to determine position to less than one meter, velocity to less than three cm/second, and attitude knowledge within 0.05 degrees.
The vehicle software is architected around Goddard Space Flight Center’s (GSFC) Core Flight Software (CFS).
GSFC designed CFS as a set of reusable software modules in a flexible framework that can be adapted to various space applications. Morpheus software developers built upon CFS by adding custom application code unique to the Morpheus vehicle and mission design.
The initial Morpheus VTB 1.0 configuration was tested from April 2011 through August 2011. In late 2011 and early 2012, the team began upgrading the VTB to the Morpheus 1.5 configuration, including sequentially higher performance HD4 and HD5 engines, an improved avionics and power distribution design, the addition of LOX/methane thrusters for roll control, and the incorporation of the ALHAT sensors and software. In August 2012, the original vehicle was lost in a test crash. The vehicle was rebuilt with over 70 upgrades and is designated as the American Institute of Aeronautics and Astronautics: SPACE 2013 Morpheus 1.5 ‘Bravo’ vehicle. This vehicle configuration is currently in testing as described in later sections. A ‘Charlie’ vehicle is also under construction.
B. Ground Systems The VTB flight complex (VFC) includes 20’ x 20’ concrete pads located on a section of the JSC antenna range near an old Apollo-era antenna tower. About 2000 feet away is the Morpheus control center for on-site field testing at JSC, the small 2-story building 18 that was formerly used for rooftop GPS testing and storage. The main upstairs room has a window that looks directly out onto the test area, making it highly suitable as the operations “front room,” configured with three rows of computer tables for operator workstations. An adjacent room serves as the “back room” for support personnel.
The operator workstations use GSFC’s Integrated Test and Operations System (ITOS) ground software. Like CFS, ITOS was developed as ground control and display software for GSFC space vehicles and has been made available to other projects at NASA.
Figure 3 – Typical Morpheus ground support equipment ITOS is individually configured on each workstation to display vehicle telemetry and information unique to each operator position.
During each test, the Morpheus Project streams mission telemetry, voice loops, and video from the testing control center to JSC’s Mission Control Center (MCC) over dedicated wireless and wired networks. From there, data and video can be made available to internal and external networks for NASA personnel and the general public.
A thrust termination system (TTS) is employed both for range safety and independent test termination purposes.
Closing either of two motorized valves in the TTS will shut off the flow of liquid oxygen and methane to the engine and terminate engine thrust. These TTS valves are completely independent from the rest of the vehicle systems and commanded using separate Ultra High Frequency (UHF) radios. The commands to initiate thrust termination are sent from a control unit located in the operations center during any live engine testing.
Ground systems also include propulsion ground support equipment (GSE). The consumables required for an engine test include liquid oxygen, liquefied natural gas, helium, liquid nitrogen, and gaseous nitrogen. The power GSE is a portable ground power cart that is used to supply power to the vehicle until the test procedures call for a switch to internal vehicle power. The ground power cart uses heavy duty batteries and can provide up to 72 amphours of power for pre- and post-test activities. The mechanical GSE includes a rented crane for tethered or hot fire / hold-down testing. For tethered tests, an energy absorber is placed between the vehicle and the crane boom arm. The energy absorber is an aluminum piston and cylinder with cardboard honeycomb material that can attenuate up to 10,000 lb. This load attenuation protects the vehicle and crane structures in the event engine thrust needs to be terminated prematurely, causing the vehicle to drop to the end of the tether.
Ground systems also include a variety of transportation assets, provided primarily by JSC Center Operations.
C. Free-Flight Testing Morpheus “free-flights” demonstrate the fully integrated flight capability of the vehicle with no restraints. Freeflight safeguards are automatic on-board aborts, remotely commanded aborts, as well as the redundant and independent TTS that can be activated by spotters who visually determine trajectory deviations. A variety of freeflight trajectories can be flown to incrementally build up to a fully functional Morpheus lander capable of flying planetary landing trajectories.
5. MORPHEUS 1.5 ‘ALPHA’ TEST CAMPAIGN The Morpheus 1.5A test campaign began in February 2012. Three hot fire tests, one ground hot fire and fourteen tether tests were performed, accumulating over 870 seconds of runtime on the HD4 engine. The tether tests were opportunities for the design team to continue to characterize and improve the interaction between the GN&C and propulsion systems. Table 2 lists the test summary for Morpheus 1.5 ‘Alpha’.
After HF5 confirmed the performance of the new HD4 engine, the team began the assessment of the integrated VTB 1.5 performance in tethered hover tests. Notable tests include TT9, which revealed a GN&C algorithm issue that caused the vehicle to exceed the altitude constraint, leading to activation of the TTS to abort the test. TT9 proved the value of the in-line energy absorber and the very robust vehicle construction in preventing damage to VTB 1.5 as it dropped to the end of the tether.
As the first test of Morpheus sitting on the launch pad in liftoff configuration, HF6 provided valuable ground effects and overpressure data, and revealed that the footpads were insufficiently insulated. This test served as a proto-qual test, intended to envelope the environments expected to be experienced during free flight launches.
Tether tests 10 through 15 demonstrated increasing vehicle controllability and stability with nominal engine shutdowns as the team refined GN&C and EMA parameters. With satisfactory vehicle performance, the ALHAT suite of sensors was integrated with the vehicle for two tether tests. This initial integration did identify some hardware and software timing discrepancies that required continued maturation once the sensors were removed from the vehicle.
With ALHAT integration testing complete, the team prepared for free flight testing by conducting one final tether test at JSC, shipping the vehicle to KSC, and then conducting a tether test at KSC’s Shuttle Landing Facility (SLF) to verify transportation did not impact vehicle readiness.
American Institute of Aeronautics and Astronautics: SPACE 2013