NASA - National Aeronautics and Space Administration

Training Flight Crew for Spacewalks
Photo credit: NASA

The Johnson Space Center offers capabilities in mission planning, crew training, flight product generation, and real-time operational support in the Mission Control Center. Our Plan-Train-Fly model incorporates over 45 years of expertise, leadership, and valuable lessons learned that creates a mission operations team of technical excellence, with the agility to fit any mission. This technical excellence is built upon our leadership culture, which provides integration of complex tasks, makes critical risk trades in safety, mission success, cost and schedule, and partners with industry to deploy innovative solutions to mitigate redesigns and ensure operable spacecraft systems.

Capabilities

• Plan
  Spaceflight Timelines
  Orbital Flight and Trajectories
  Spacecraft Monitoring System Parameters
  Spacecraft Design for Operations Considerations
• Train
  Flight Crews for Spacewalks
  Flight Crews for Spacecraft Systems
  Spaceflight Simulation Systems
• Fly
  Real-Time Spaceflight Anomaly Risk Analysis
  Spacecraft Control Systems for Mission Control
  Worldwide Spacecraft Communications Network
  Flight Procedures and Check List

The Johnson Space Center has extensive facilities for testing, training and executing human space missions. These facilities can support the entire mission development cycle, from early design and ops concepts testing to training for crews and flight control teams to providing physical control room space for real-time support. JSC facilities represent the best of over 50 years of successful spaceflight along with new technology investments implemented to leverage industry solutions and provide the best platform possible for mission support.

Training Flight Crews for Spaceflight Systems
Photo credit: NASA

The Johnson Space Center is the world leader in space operations, providing technical leadership and partner integration since 1964. With over 160 successful human space missions planned and executed, our teams have a proven record of cost effective mission planning and analysis for a variety of mission types. We provide scalable solutions to fit any size mission and infuse innovative ideas and new technologies to address unique mission needs. We have extensive expertise that can be utilized in a wide spectrum of projects or vehicles, supporting both large programs and small projects, as well as analog mission research.

Our experience with integration of spaceflight elements spans across systems, vehicles, and programs, as well as government, industry, and international partners. We have experience with configuration management of spaceflight hardware, software, facilities, plans and procedures. Our comprehensive training and certification of flight crew, operations, and instructor personnel has resulted in decades of successful human spaceflight missions. Our product development and analysis teams focus not only on nominal activities, but failures and contingencies as well.

Capabilities

• Product development and verification, including mission timelines, flight rules, and crew and ground procedures
• Analysis and modeling of vehicle performance, consumables and human / vehicle interfaces
• Flight design of launch, orbit, and entry flight trajectories and associated risk controls
• Operations tools design, development and testing, including onboard and ground software
• Training curriculum development of generic vehicle and mission specific operations
• Flight controller training in cost-effective system, integrated flight control team simulation environments
• Mission readiness assessments
• Safety and Risk Assessment

Training Flight Crews for In-Flight Procedures
Photo credit: NASA

The Johnson Space Center has an experienced operations team prepared for and capable of reacting to any situation, providing safety, mission success, and project flexibility. We have command and control expertise covering all phases of flight (launch, landing, orbit, rendezvous, dock/undock, reboost, berth/unberth, robotics, and spacewalks). Our teams have successfully controlled multiple spacecraft simultaneously. Our tools allow us to analyze failures, compare results, and make revisions in a timely manner.

The proven real-time decision making skills of our personnel ensure mission success. Every mission requires critical risk trades in safety, mission success, cost, and schedule. Our rapid mission timeline management allows us to quickly respond to anomalies and unplanned deviations. In addition, our comparisons of real time usage versus pre-flight predictions allow us to maximize consumables (propulsion, power, water, atmosphere, food) and optimize trajectories (orbital debris avoidance, vehicle performance, center of gravity determination, rendezvous maneuver planning).

Capabilities

• Real-time flight operations
• Day of launch development and operations
• Landing / recovery support
• Timeline development and execution
• Navigation / orbit determination
• Collision Avoidance
• Operations integration
• Command and control
• In-flight emergency response
• Anomaly diagnosis, tracking, response and resolution

Virtual Reality System
Photo credit: NASA

The Johnson Space Center operations teams partner with spacecraft designers to reach cost-effective and sustainable solutions. We apply real operational scenarios to define and validate operations concepts. Our operability assessments help to identify a design's operational strengths and risks, as well as the integrated effect on crew and vehicle safety. When design challenges arise our teams rely on decades of real-time human spaceflight experience to develop alternative solutions or operational workarounds.

Our real-time flight experience is also well suited for the test and verification environment. We provide test conductors and operators who apply real-time decision making skills to maximize test effectiveness and efficiency. We develop test procedures that fully exercise an integrated system's capabilities and provide safe and effective human-machine integration. By defining baseline and minimum equipment configurations we offer a better understanding of system reliability and help ensure mission success.

Capabilities

• Operations concept and requirements development and validation
• Multi-system integration and cross discipline systems engineering analysis
• Mission event sequencing
• Operational workaround development
• Onboard and ground capability design trades
• Command and telemetry definition
• Power and data channelization
• Cockpit, displays and controls design
• Integrated launch vehicle / spacecraft design and analysis

Orbital Debris Model around Earth
Photo credit: NASA

Controlling the growth of the orbital debris population is a high priority for NASA, the United States, and the major space-faring nations of the world to preserve near-Earth space for future generations.

The Johnson Space Center conducts a full range of research activities to limit the growth of orbital debris. NASA produces many products that can be used by spacecraft and mission designers to ensure that their missions are compliant with standards and best practices which protect the earth orbital environment from unacceptable growth of human-made orbital debris.

Measurements of the current environment

As much as possible, estimates of the current orbital debris environment are based on measurements. This emphasis on data driven modeling helps ensure that model results have a solid, reality based, starting point.
Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. Data is acquired using ground-based radars and optical telescopes, space-based telescopes, and analysis of spacecraft surfaces returned from space. Some important data sources have been the U.S. Space Surveillance Network, the Haystack X-Band Radar, and returned surfaces from the Solar Max, the Long Duration Exposure Facility (LDEF), the Hubble Space Telescope (HST) and the Space Shuttle spacecraft. The data provide validation for the environment models and identify the presence of new sources.

Modeling of the future environment

NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Engineering models, such as ORDEM2000, can be used for debris impact risk assessments for spacecraft and satellites, including the International Space Station and the Space Shuttle. This engineering model is available to any user at the Orbital Debris Website, http://orbitaldebris.jsc.nasa.gov.

Evolutionary models, such as LEGEND, are designed to predict the future debris environment. They are reliable tools to study how the future debris environment reacts to various mitigation practices, including scenarios involving active debris removal. The operation of LEGEND requires special training and elaborate databases and is not available to other users.

Mitigation Orbital debris damage seen during Hubble Space Telescope repairs.
Photo credit: NASA

Mitigation measures can take the form of curtailing or preventing the creation of new debris, designing satellites to withstand impacts by small debris, and implementing operational procedures such as using orbital regimes with less debris, adopting specific spacecraft attitudes, and even maneuvering to avoid collisions with debris.

NASA has developed a software suite specifically designed to allow spacecraft and mission planners assess compliance with NASA-STD 8719.14, Process for Limiting Orbital Debris. Although specifically designed for meeting the NASA mitigation standards, the tool, NASA Debris Assessment Software (DAS) can be useful for other agencies or commercial users. DAS is also available to all on the NASA Orbital Debris website.

Reentry Survivability

Due to the increasing number of objects in space, NASA and the international aerospace community have adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of post-mission disposal is to allow the reentry of these spacecraft, either from natural orbital decay (uncontrolled) or controlled entry. One way to accelerate orbital decay is to lower the perigee altitude so that atmospheric drag will cause the spacecraft to enter the earth's atmosphere more rapidly. However, in such cases the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally is achieved by using more propellant with a larger propulsion system to cause the spacecraft to enter the atmosphere at a steeper flight path angle. The vehicle will then enter the atmosphere at a more precise latitude and longitude, and the debris footprint can be positioned over an uninhabited region, generally located in the ocean.

After spacecraft (or parent body) breakup, individual components, or fragments, will continue to lose altitude and receive aeroheating until they either demise or survive to impact the Earth. Spacecraft components that are made of low melting-point materials (e.g., aluminum) will generally demise at higher altitudes than objects that are made of materials with higher melting points (e.g., titanium, stainless steel, beryllium, carbon-carbon). If an object is contained inside of a housing, the housing must demise before the internal object receives significant heating. Many objects have a very high melt temperature such that they do not demise, but some can be so light (e.g., tungsten shims) that they impact with a very low velocity. As a result, the kinetic energy at impact is sometimes under 15 J, a threshold below which the probability of human casualty is very low.

There are two NASA methods to compute the reentry survivability of spacecraft components. DAS includes a conservative, easy-to-use tool. However, if the DAS tool indicates possible non-compliance with human casualty risks, the Object Reentry Survival Analysis Tool (ORSAT) provides a more accurate, higher fidelity model.

On 21 January 2001, a Delta 2 third stage, known as a PAM-D (Payload Assist Module - Delta), reentered the atmosphere over the Middle East. The titanium motor casing of the PAM-D, weighing about 70 kg, landed in Saudi Arabia about 240 km from the capital of Riyadh.
Photo credit: NASA The ORSAT code uses integrated trajectory, atmospheric, aerodynamic, aerothermodynamic, and thermal/ablation models to perform a complete satellite or launch vehicle upper stage component analysis in determining the impact risk. A three-degrees-of-freedom trajectory is used with the 1976 U.S. standard atmosphere, MSISe-90 atmosphere, or the GRAM-99 atmosphere to model various types of object shapes in either spinning or tumbling modes. Drag coefficients of these objects are considered from hypersonic to subsonic speeds to obtain the kinetic energy of objects at ground impact. Stagnation point continuum heating rates are obtained for spherical objects and are adjusted for other bodies and for rarefied flow regimes. Both lumped mass and 1-D heat conduction models may be used to compute the surface temperature. The object is considered to demise when its absorbed heat reaches the material heat of ablation.

Thermal properties for 80 materials are included in a database in ORSAT, with temperature-varying properties listed for thermal conductivity, specific heat, and surface emissivity. For objects that are on the threshold of demise or survival, parameters such as oxidation efficiency, initial temperature, surface emissivity, number of layers, dimensions, or breakup altitude may be varied in a single run to obtain the critical demise/survival point of a component. Good engineering judgment is applied in the parametric analysis to compute the best predicted total debris casualty area. The impact risk is then calculated to determine whether the satellite or upper stage is compliant with the NASA Standard 8719.14. Similar to LEGEND, ORSAT requires operator expertise and training and is not available to outside users.

International Space Station MMOD shield locations (HVIT geometry model); each color represents a different level of impact risk. A red color indicates high impact risk from MMOD, and blue color indicates low impact risk. Based on impact analysis results, heavier/more capable MMOD shielding is used in red areas, and lighter/less capable shielding in blue areas.
Photo credit: NASA

The Johnson Space Center and the NASA White Sands Test Facility's Remote Hypervelocity Test Laboratory (RHTL) compose a team dedicated to evaluating the environmental effects from micrometeoroid and orbital debris (MMOD) impacts on orbiting spacecraft. This team has the in-house ability to prepare and plan hypervelocity impact tests, perform post-test damage analysis, conduct computer impact simulations and spacecraft risk assessments. The team designs and tests turnkey solutions for mitigating MMOD impact effects on spacecraft.

The Problem

The near-Earth space environment is cluttered with manmade orbital debris and naturally occurring meteoroid particles. Most of the debris particles are very small; however, they are moving at velocities averaging up to 15 kilometers per second and can pose significant impact hazard for orbiting spacecraft and personnel. Although some of these particles eventually fall back to Earth and burn up in the atmosphere, new debris particles are frequently added to the environment by such sources as exploding spacecraft and discharged spacecraft waste. The overall trend is that the near Earth orbital debris environment is gradually getting worse.

The Solution

Engineers and technicians design, test, and analyze spacecraft systems to reduce the risk from MMOD particle impact. The team has performed thousands of hypervelocity impact tests that have yielded numerous efficient and effective shielding designs, as well as detailed data on the effect of MMOD impact on various spacecraft components. The team applies state-of-the-art computer codes to improve the design of spacecraft MMOD protection systems and develop operational guidelines to reduce MMOD damage.

Capablilites

• MMOD shielding design
• Hypervelocity impact testing
• Hypervelocity impact computer simulation
• MMOD shield ballistic limit determination
• MMOD impact/penetration risk assessment