2.0 RLV OPERATIONS CONCEPT

2.1 Background

The Access to Space Advanced Technology Team (Option 3) performed extensive background investigation into the driving factors and approaches for reducing the cost of space launch operations. They developed four cornerstones of a reduced cost approach. These are:

• Define the mission narrowly to transportation only.
• Apply modern technology to design a simple vehicle with less complex subsystems and fewer elements.
• Avoid flight-by flight certification through a prototype flight test program
• Adopt a management philosophy that empowers individuals to replace today's philosophy of decision by committee.

In further investigations to develop these concepts in more detail the Access to Space Advanced Technology Team analyzed the SR-71 aircraft, tactical aircraft, intercontinental missiles (air and sea based), advanced commercial aircraft and experimental vehicles to develop a benchmark for space launch programs. The following represent the lessons learned from these bench mark program investigations.

• Successful programs have separated development from operations.
• Simpler vehicles are more reliable.
• Fleet certifications are better than flight certifications.
• Mission surety does not require huge manning.
• Designed in operability reduces manning required to prepare sophisticated vehicles for flight.
• Mature and reliable vehicle health management systems do exist and are critical for:

  - Monitoring system performance in exotic environments.

  - Reducing the need for extensive testing.

  - Expediting ground processing.

• Individual responsibility and empowerment leads to lowered operations manning

  - a non-touch to touch manpower ratio of 3:1 is completely adequate to operate high technology aerospace equipment with confidence.

2.2 Vehicle Operations Concept

• Mission, vehicle design, fleet size, operational timelines, facilities, equipment and manpower must be developed in conjunction with each other (not as groundrules, assumptions or requirements) in order to arrive at a program with optimized cost, capability and performance.
• Development should be focused on the productivity of a single vehicle within a fleet size which is unspecified.
• The dependence of the vehicle on facility and GSE architecture should be at a minimum (e.g. single site bare pad/runway).
• Ground activities between flights should be required only to replenish consumables and install cargo.
• Autonomous vehicle capabilities should confirm vehicle condition during and between flights with no physical contact to relay status to a spaceport control capability.
• The spaceport provides consumables servicing and cargo handling services, as well as landing, taxi and take-off flight planning and monitoring (air traffic control) on a routine basis.
• Commercial aircraft-like vehicle certification for repetitive commercial flight operations should be achieved to free the system from test range constrained operation.
• The spaceport provides off line maintenance capability on an as needed basis.
• Non-touch to touch manpower ratio of less than 3:1.
• Empowered management: program manager during development, crew chief during ground operations, flight manager during flight operations.

2.3 Payload Operations/Accommodations Concept

The needs of payload customers must be taken into consideration for any commercially-operated RLV venture to compete successfully in the launch services market. On-time departure (launch) is of paramount importance to customers. The payload should be transparent to the vehicle (any available vehicle in the fleet should be able to launch any payload). Based on lessons learned from processing both shuttle and ELV payloads, the following items are for consideration for arriving at affordable customer needs.

• A standard set of essential, simplified payload interfaces with autonomous validation capability will be provided. Special requirements will be accommodated by the payload using the standard vehicle interfaces.
• The payload and vehicle integration process should be standardized and highly automated.
• Vehicle and ground system designs should minimize impacts to payload design and operations due to changing orientations and load axes.
• Ground facility and equipment requirements for standalone payload processing should not be driven by vehicle concepts.
• The vehicle and corresponding operations concepts should be defined such that payload access or passenger ingress/egress accommodations are not a significant operational issue.

2.4 Mission Design and Flight Operations Concept

Mission design and flight operation is autonomous by design. After loading-in the target orbit and the stay time, a computer designs trajectories and determines timelines for orbital maneuvers, deorbits, etc. This is possible because the vehicle will perform a set of standard tasks--payload delivery, rendezvous and dock, stay on station for some length of time, and return to any launch/landing spaceport. Any unique tasks for a mission will be handled by the payload. There will be very limited payload-vehicle interfaces. The need for various interfaces will be subject to a trade when identified. The payload assumes the responsibility to perform self test/checkout to verify its functional integrity prior to deployment from the RLV and communicates to the control computer if it is to remain on-board for the return flight.

Flight operations are automated. Generation and verification of an ascent trajectory that satisfies vehicle envelopes is automatic. Autonomous communication with the ground weather station yields day of launch ascent and landing site winds for a computer program that makes automatic go/no-go decisions. The computer informs the ground control tower of go/no-go status. The extent of the automated computer work to be done on-board the vehicle, versus on the ground, is subject to a trade, with the lowest operating cost the determining factor.

The vehicle is robust in minimizing the need for redundant hardware required for reliability. Where fault tolerance is necessary for reliability, the vehicle automatically detects and reconfigures. Navigation is onboard and autonomous, except for nearby GPS transmitters providing data during the rendezvous and approach and landing phases. GPS operation during ascent transmits position data to avoid use of range safety radars. Relative GPS is used during rendezvous. There is no dedicated software maintenance function required to support operation.

The vehicle is automated with respect to abort mode recognition, rendezvous and dock, deorbit, sequencing, and reconfiguration of vehicle systems. Vehicle robustness provides the capability to always abort either to any launch/landing spaceport or to orbit if necessary. The only uploads from the ground that involve human interaction are mode commands, such as "perform collision avoidance maneuver" or notifications due to unusual ground system failures. These communications are from the ground control tower. The determination of these commands is automated, given a human mode change decision when necessary. Autonomous uploads consist of items such as landing site weather data and occasional uploads of rendezvous-target state vectors. Failed docking attempts with the Space Station are handled automatically. The vehicle station-keeps in close proximity to the Space Station.

Return to KSC Next Gen Site

Edgar Zapata, NASA Kennedy Space Center

Shuttle Process Engineering Directorate, Fluid Systems Division