- Parabolic Arc
- November 29, 2023
Additional Artemis I Test Objectives to Provide Added Confidence in Capabilities
NASA Mission Update
During Artemis I, NASA plans to accomplish several primary objectives, including demonstrating the performance of the Orion spacecraft’s heat shield from lunar return velocities, demonstrating operations and facilities during all mission phases from launch countdown through recovery, and retrieving the crew module for post-flight analysis. As the first integrated flight of the Space Launch System rocket, Orion spacecraft, and the exploration ground systems at NASA’s 21st century spaceport in Florida, engineers hope to accomplish a host of additional test objectives to better understand how the spacecraft performs in space and prepare for future missions with crew.
Accomplishing additional objectives helps reduce risk for missions with crew and provides extra data so engineers can assess trends in spacecraft performance or improve confidence in spacecraft capabilities. Some of the additional objectives planned for Artemis I include:
On the European-built service module, Orion is equipped with 24 reaction control system (RCS) thrusters, small engines responsible for moving the spacecraft in different directions and rotating it. The modal survey is a prescribed series of small RCS firings that will help engineers ensure the structural margin of Orion’s solar array wings during the mission. Flight controllers will command several small firings of the engines to cause the arrays to flex. They will measure the impact of the firings on the arrays and evaluate whether the inertial measurement units used for navigation are experiencing what they should. Until the modal survey is complete, large translational burns are limited to 40 seconds.
Optical navigation camera certification
Orion has an advanced guidance, navigation, and control (GN&C) system, responsible for always knowing where the spacecraft is located in space, which way it’s pointed, and where it’s going. It primarily uses two star trackers, sensitive cameras that take pictures of the star field around Orion, the Moon, and Earth, and compares the pictures to its built-in map of stars. The Optical navigation camera is a secondary camera that takes images of the Moon and Earth to help orient the spacecraft by looking at the size and position of the celestial bodies in the image. At several times during the mission, the optical navigation camera will be tested to certify it for use on future flights. Once certified, the camera also can help Orion autonomously return home if it were to lose communication with Earth.
Solar array wing camera Wi-Fi characterization
The cameras affixed to the tips of the solar array wings communicate with Orion’s camera controller through an on-board Wi-Fi network. Flight controllers will vary the positioning of the solar arrays to test the Wi-Fi strength while the arrays are in different configurations. The test will allow engineers to optimize how quickly imagery taken by cameras on the ends of the arrays can be transmitted to onboard recorders.
Crew module/service module surveys
Flight controllers will use the cameras on the four solar array wings to take detailed photos of the crew module and service module twice during the mission to identify any micrometeoroid or orbital debris strikes. A survey conducted early on in the mission will provide images soon after the spacecraft has flown beyond the altitude where space debris resides and a second survey on the return leg will occur several days before reentry.
Large file delivery protocol uplink
Engineers in mission control will uplink large data files to Orion to better understand how much time it takes for the spacecraft to receive sizeable files. During the mission, flight controllers use the Deep Space Network to communicate with and send data to the spacecraft, but testing before flight hasn’t including using the network. The test will help inform engineers’ understanding of whether the spacecraft uplink and downlink capability is sufficient to support human rating validation of end-to-end communication prior to Artemis II, the first flight with astronauts.
Star tracker thermal assessment
Engineers hope to characterize the alignment between the star trackers that are part of the guidance, navigation and control system and the Orion inertial measurements units, by exposing different areas of the spacecraft to the Sun and activating the star trackers in the different thermal states. The measurements will inform the uncertainty in the navigation state due to thermal bending and expansion which ultimately impacts the amount of propellant needed for spacecraft maneuvers during crewed missions.
Radiator loop flow control
Two radiator loops on the spacecraft’s European Service Module help expel heat generated by different systems throughout the flight. There are two modes for the radiators. During speed mode, the radiator pumps operate at a constant speed to help limit vibrations and is the primary mode used during Artemis I and during launch for all Artemis flights. Control mode allows for better control of the radiator pumps and their flow rate, and will be used on crewed missions when more refined control of flow through the radiators is desired. This objective will test control mode to provide additional data about how it operates in space.
Solar array wing plume
Depending on the angle of Orion’s solar array wings during some thruster firings, the plume, or exhaust gasses, from those firings could increase the arrays’ temperature. Through a series of small RCS firings, engineers will gather data to characterize heating of the solar array wings.
Liquid propellant kept in tanks on the spacecraft moves differently in space than on Earth because of the lack of gravity in space. Propellant motion, or slosh, in space is hard to model on Earth, so engineers plan to gather data on the motion of the propellant during several planned activities during the mission.
Search acquire and track (SAT) mode
SAT mode is an algorithm intended to recover and maintain communications with Earth after loss of Orion’s navigation state, extended loss of communications with Earth, or after a temporary power loss that causes Orion to reboot hardware. To test the algorithm, flight controllers will command the spacecraft to enter SAT mode, and after about 15 minutes, restore normal communications. Testing SAT mode will give engineers confidence it can be relied upon as the final option to fix a loss of communications when crew are aboard.
During entry of the spacecraft through Earth’s atmosphere, a prescribed series of 19 reaction control system firings on the crew module will be done to understand performance compared to projected data for the sequence. Engineers are interested in gathering this data during high heating on the spacecraft where the aerothermal effects are largest.
Integrated Search and Rescue Satellite Aided Tracking (SARSAT) functionality
The SARSAT test will verify connectivity between beacons to be worn by crew on future flights and ground stations receiving the signal. The beacons will be remotely activated and powered for about an hour after splashdown and will also help engineers understand whether the signal transmitted interferes with communications equipment used during recovery operations, including Orion’s built-in tri-band beacon which transmits the spacecraft’s precise location after splashdown.
Ammonia boiler restart
After Artemis I splashdown, Orion’s ammonia boiler will be turned off for several minutes then restarted to provide additional data about the system’s capability. Ammonia boilers are used to help control the thermal aspects of the spacecraft to keep its power and avionics systems cool, and keep the interior of the crew module at a comfortable temperature for future crews. In some potential contingency landing scenarios for crewed missions, crews may need to turn off the ammonia boiler to check for hazards outside the spacecraft, then potentially turn it back on to provide additional cooling.
Engineers will perform additional tests to gather data, including monitoring the heatshield and interior components for saltwater intrusion after splashdown. They also will test the GPS receiver on the spacecraft to determine the spacecraft’s ability to pick up the signal being transmitted around Earth, which could be used to augment the spacecraft’s ability to understand its positioning in the event of communications loss with mission controllers.
Collectively, performing additional objectives during the flight provides additional information engineers can use to improve Orion as NASA’s spacecraft that will take humans to deep space for years to come.