HEO Committee Outlines TDRS Replacement, Improved Artemis Testing

by Thomas Burghardt

Updated plans in Low Earth Orbit and beyond now include replacing the Tracking and Data Relay Satellite (TDRS) constellation and flight testing Orion’s rendezvous and docking systems. These goals were highlighted in a meeting of the Human Exploration and Operations (HEO) committee of the NASA Advisory Council Wednesday.

(Lead image by Mack Crawford for NSF/L2)

The topics discussed by the committee surround a common theme of learning from past successful commercial spaceflight programs, especially the Commercial Cargo and Crew programs, and applying those lessons to achieving the ambitious goals of the Artemis program.

Interestingly, NASA has also aimed to commercialize its communications infrastructure in Earth orbit. In order to support missions near Earth, NASA uses a combination of the Near Earth Network and the Space Network to send and receive communications and telemetry data.

The Near Earth Network is an array of ground stations on Earth, currently about 70% of which are commercially operated for NASA, rather than operated by NASA directly. Doug Loverro, Associate Administrator for Human Exploration and Operations, has identified a goal of 100% commercialization by 2023.

The current TDRS fleet. Two satellites have been maneuvered into graveyard orbits for retirement, while the other ten remain operational. – via NASA

Loverro also stated that NASA has purchased its final Tracking and Data Relay Satellite. TDRS is a constellation of ten satellites in geostationary orbit used to communicate with spacecraft in Earth orbit, the newest of which was launched in August of 2017. By 2030, Loverro says the TDRS fleet and the rest of NASA’s Space Network will become 100% commercial.

Looking to the future, Loverro also mentioned the possibility of applying a similar goal to NASA’s Deep Space Network, the ground facilities which support missions beyond Low Earth Orbit.

Commercializing LEO has been a priority in recent years to reduce costs and allow the agency to focus on more ambitious destinations. The Commercial Cargo program, now entering its second phase, has successfully enlisted the SpaceX Cargo Dragon and Northrop Grumman Cygnus spacecraft to deliver experiments and supplies to the International Space Station since the SpaceX CRS-1 mission in 2012, with Sierra Nevada’s Dream Chaser spacecraft set to join the fleet in 2021.

NASA then took a similar approach to crew transportation with the Commercial Crew program, developing two crew spacecraft which are on the brink of operational flight. Boeing’s Starliner spacecraft is set to conduct another uncrewed test flight later this year, while the first SpaceX Crew Dragon spacecraft to carry humans has been integrated with its Falcon 9 rocket for the Demo-2 launch on May 27.

The success of these programs was cited by multiple committee members as points of confidence in the increasingly commercialized Artemis program, especially for Human Landing System (HLS) development. But they also referenced lessons learned from the first uncrewed test flight of Starliner, which failed to rendezvous and dock with the International Space Station.

In order to more thoroughly test the Orion spacecraft’s docking systems, the Artemis II mission will now include a Rendezvous and Proximity Operations (RPO) demonstration. Details of the demonstration are still being developed, including whether an actual docking will occur or a different test of the relevant systems.

The demonstration will occur during the established Artemis II mission plan, which calls for a crewed mission on a free return trajectory around the moon. If a target docking spacecraft is desired, NASA has considered the use of SpaceX’s Dragon XL spacecraft, which NASA will utilize to deliver cargo to the Lunar Gateway station in lunar orbit.

Rendering of the SpaceX Dragon XL spacecraft to be used for Gateway Logistics Services, which could also be used as a target docking spacecraft for Orion – via SpaceX

The Artemis II mission will launch no earlier than 2022, following the Artemis I test flight of Orion and the SLS rocket no earlier than 2021. Artemis I will send an uncrewed Orion spacecraft into a Distant Retrograde Orbit (DRO) around the moon, followed by a return to Earth.

A single item noted by the committee was the effect of the COVID-19 pandemic on testing of the Artemis I SLS core stage. Prior to shutting down work at the Stennis Space Center, teams were ten days ahead of schedule to ship the core stage to the Kennedy Space Center by November of this year. That timeline is now expected to slip.

The Artemis I and II missions, once successfully completed, will set the stage for the first human landing on the moon since Apollo 17. NASA is working to maintain a timeline that would see a landing in 2024, and the development of the Human Landing System (HLS) is on the critical path.

In discussing risks to HLS development, Program Manager Dr. Lisa Watson-Morgan pointed out that all three HLS proposals rely on unproven launch vehicles. The Blue Origin-led National Team and Dynetics utilize the not yet flown New Glenn and Vulcan rockets, while SpaceX’s Starship vehicle requires a Super Heavy booster to reach orbit.

Watson-Morgan also provided new details on the proposed HLS designs. The Dynetics HLS will require multiple launches, due to the need to preposition Modular Propellant Vehicles (MPVs) to fuel the lander.

SpaceX’s proposal, which has resulted in a variant of their Starship vehicle with an airlock 26 meters above the surface, originated with a three element design. SpaceX has since evolved the proposal to a single element Starship vehicle.

Render of the Starship HLS on the lunar surface – via SpaceX

Beginning in November, NASA will evaluate the progress of the three providers in preparation to a down-selection in February 2021. The number of providers which will fly demonstration and operational missions to the lunar surface will be determined during this period, and could be either one, two, or all three providers.

The Artemis III landing mission will not utilize the Lunar Gateway station, in order to minimize technical and schedule risk. Instead, the HLS will dock directly to the Orion spacecraft in lunar orbit. The crew will move into the HLS, conduct their mission on the lunar surface, and then return to Orion for the ride back to Earth. The risk with this mission plan is also minimized through the RPO demonstration on Artemis II.

In the interests of further risk and cost reduction, the Gateway program has also made the decision to integrate the Power and Propulsion Element (PPE) and the Habitation And Logistics Outpost (HALO) on the ground for a single launch, instead of assembling the modules in space. The launch is currently scheduled for no earlier than November 2023 aboard a commercial launch vehicle.

HEO committee meeting slide showing the launch configuration of the integrated Lunar Gateway – via NASA

A request for launch services proposals for the mission was released on May 6, and a selection is expected to be made by NASA’s Launch Services Program by late fall of 2020. Gateway Program Manager Dan Hartman, when asked if NASA ensured that a commercial launch provider would be able to deliver launch services for an integrated Gateway, stated that NASA was highly confident that at least one provider would be capable of such a launch, using an enlarged payload fairing.

SpaceX has proposed developing an enlarged fairing for their Falcon Heavy launch vehicle as part of the Air Force’s National Security Space Launch (NSSL) program. Hartman then reiterated that NSSL Phase 2 awards are expected this summer, before the expected launch services selection for the Gateway. These notes by the program manager seem to strongly indicate that Falcon Heavy is predicted to be selected, although other options could appear in response to the request for proposals.

Hartman also mentioned the future delivery of a Canadian robotic arm to the Gateway, likely aboard a Dragon XL cargo spacecraft. That addition could occur around the 2026 timeframe, among post-Artemis III missions to the moon.

Doug Loverro stressed that every Artemis mission beyond the initial landing would be in support of future human missions to Mars.

Related Articles