NASA Advances Plans for Robotic and Crewed Moon Landings

by Thomas Burghardt

NASA’s plans to land both robots and humans on the moon have taken several steps forward. A solicitation for scaled-up robotic landers has been released by the Commercial Lunar Payload Services program, and plans for human moon landers have changed to make room for more innovation by private partners. NASA will be supporting the development of these vehicles with new partnerships, aiming to mature technologies for both Moon and Mars missions.

Scaling Up Robotic Landers

The Commercial Lunar Payload Services (CLPS) program is how NASA plans to land uncrewed research missions on the moon in support of the crewed Artemis program. Providers are asked by NASA to provide end-to-end transportation from Earth to the lunar surface, including both launch services and a lunar lander.

The first phase of the program saw nine companies selected to be eligible to bid for transportation services. Of these nine providers, three were selected as part of the first task order to deliver NASA payloads to the lunar surface: Orbit Beyond, Astrobotic, and Intuitive Machines.

The three robotic landers selected for the first CLPS task order, from left to right: Astrobotic, Intuitive Machines, and Orbit Beyond – via NASA

Orbit Beyond was expected to be the first of these providers to launch their mission under the first task order, no earlier than 2020. However, due to “internal corporate challenges” that precluded Orbit Beyond’s ability to fly on time, NASA has released the provider from the first contract.

Orbit Beyond is still eligible to compete for future CLPS task orders, along with the nine other selected providers, and the first landing under the CLPS program by either Astrobotic or Intuitive Machines is on track to occur in 2021.

When Intuitive Machines was selected by NASA, they also announced their selection of SpaceX’s Falcon 9 rocket to launch their Nova-C lander. Astrobotic had not yet selected a launch vehicle. That changed this week when Astrobotic selected United Launch Alliance’s Vulcan Centaur rocket. Peregrine will be on the maiden flight of ULA’s new launcher and will lift off from Cape Canaveral, Florida in 2021.

A new solicitation released by NASA is now calling for additional companies that can become eligible for task orders, alongside the already selected providers. The new companies are being asked to develop vehicles that can land larger and heavier payloads on the lunar surface in support of science and exploration goals.

One intriguing detail included in the solicitation is the possibility of co-manifesting payloads aboard the lunar lander. It is specified that providers can utilize capacity not used by NASA for other payloads, whether they belong to the provider or a commercial customer, as long as they do not interfere with the NASA payloads.

This could provide further incentive and opportunity for providers as they scale up their landers for larger payload capacities. Proposals for this solicitation are due August 29, with contract award(s) anticipated on October 15.

Opening the Door for Integrated Human Landers

Informed by research conducted and vehicles developed under CLPS, the Artemis program is preparing to return humans to the lunar surface. When NASA released the original solicitation for the Human Landing System (HLS), the vehicle landing on the lunar surface was broken down into three elements.

The transfer, descent, and ascent elements were expected to be built by different companies, launched separately, and assembled at the Gateway in lunar orbit.

NASA has now revised the solicitation to allow companies to propose systems which integrate multiple elements into a single-vehicle. A Concept of Operations document released with the updated solicitation details the requirements and constraints pertaining to the HLS, and the role that the vehicle will play in Artemis missions.

Overview of the profile for crewed lunar surface missions using the HLS – via NASA

The Gateway will still act as a staging point for missions to the lunar surface, including the assembly of the HLS if necessary. HLS elements will be launched aboard either a commercial rocket or the Space Launch System, with the launch vehicle responsible for Trans-Lunar Injection.

The HLS will utilize NASA’s Near Earth Network for communications in Low Earth Orbit. For Trans-Lunar Injection and beyond, communications will switch to the Deep Space Network.

A low energy mission profile can allow the HLS to efficiently insert into the Gateway’s Near-Rectilinear Halo Orbit (NRHO), a trajectory that lasts 120 days or longer. An alternate trajectory including a lunar flyby can reach the Gateway in only a few days but requires more energy.

The initial configuration of the Gateway will only include assets required to enable a crewed landing by 2024. This configuration will have two docking ports, one for the Orion crew vehicle and one for the HLS. More docking ports will be added as the Gateway and the Artemis program evolve into a more sustainable capability.

Render of a possible initial configuration for the Gateway, including an Orion spacecraft, a Northrop Grumman habitat, and a Maxar Power and Propulsion Element – via Mack Crawford for NSF/L2

If the HLS requires assembly at the Gateway, other elements can loiter in the vicinity of the Gateway without docking. This would involve a minimum distance from the gateway and active control of the element. Notably, NASA says that the Canadian Space Agency’s robotic arm will not be available for berthing or assembling vehicles in the Gateway’s initial configuration.

While no docking rules have been written for the HLS yet, the rules pertaining to vehicles visiting the International Space Station (ISS) provide insight into how docking with the Gateway might work. Currently, crewed spacecraft cannot be berthed to the ISS because of a possibility of the robotic arm failing and stranding the crew.

Thus, all crewed vehicles must dock, not berth, even once the configuration of the Gateway evolves to include the robotic arm. Uncrewed elements of the HLS may be captured by the robotic arm and berthed, once the arm is operational.

Once the HLS is assembled and docked to the Gateway, checkouts of HLS readiness for descent and landing will be conducted, prior to the crew’s launch from Earth. Once the HLS is ready, the crew will launch from Earth in the Orion spacecraft aboard the Space Launch System, on a fast trajectory to the Gateway.

Render of the first Artemis crew preparing to depart Low Earth Orbit aboard Orion – via Mack Crawford for NSF/L2

Descending to the Surface

In the initial capability phase, only two of Orion’s four crew members will board the HLS to descend to the surface, with the other two staying aboard Gateway. Sustainable phase missions will include all four crew flying to and from the lunar surface.

The HLS is required to accommodate internal volume and equipment for spacesuit assembly and checks, as the Gateway will not have suit servicing hardware in the initial capability phase. The HLS will also require either an airlock or the ability to depressurize and repressurize the cabin, in order to support lunar surface EVAs.

Once all checks are complete, the HLS will maneuver from the Gateway’s NRHO to a Low Lunar Orbit (LLO). This transit will nominally last 12 hours. NASA anticipates that a three-revolution loiter in LLO will be required to update the vehicle’s navigation systems sufficiently to achieve 50-meter landing precision. That level of precision is a long term objective, with an initial goal of 100-meter precision. The initial focus will also be limited to polar landings, eventually evolving to landing at any point on the lunar surface.

From Low Lunar Orbit, the HLS will progress through four phases of descent to the lunar surface. The first phase, Descent Orbit Initiation, will begin lowering the HLS orbit’s perilune. Then, during Powered Descent Initiation, the HLS will slow enough for its trajectory to intercept the lunar surface and for the lander to reach a sufficient altitude for the Approach phase.

During Approach, the vehicle will perform a slew maneuver to allow the crew to view the landing site. Finally, Terminal Descent and Touchdown is the vertical descent to the surface, touching down at a targeted velocity.

If a problem occurs during any phase of descent or on the lunar surface, the HLS is expected to be capable of aborting and returning the crew to the Gateway. Likewise, if a problem arises during ascent from the surface, the HLS must include a capability to abort to a stable LLO to await rescue.

Render of a possible Human Landing System supporting a lunar surface EVA – via NASA

While on the surface, the crew will live and work out of the HLS for as long as six and a half days during the initial capability phase. Two crew members will execute up to five EVAs per mission to pursue research and exploration goals. NASA specifies that the HLS must support an EVA duration capability of eight hours, with eight to twelve hours between EVAs to recharge the suits.

Once all four crew members can fly to the lunar surface, the two EVA crew will communicate with the crew in the lander, who will be communicating with Earth through the Deep Space Network. In this respect, the HLS will act as a relay and control center for lunar surface EVAs, since the EVA suits will not have direct communication with controllers on Earth.

Like the descent, the ascent from the lunar surface to the gateway is separated into four phases. The Powered Ascent phase to LLO will precede a Loiter phase to correctly phase with the Gateway’s orbit. Then, a Cruise phase to transit from LLO to NRHO. Finally, the Rendezvous and Docking phase, which will follow the same docking rules as the HLS’s initial arrival at the Gateway.

The entire Earth-to-Earth round trip mission duration for the crew must be less than 30 days according to the HLS solicitation. While the HLS must be reusable to be sustainable, the initial capability described by NASA does not require reuse. Any elements not initially reusable must be properly disposed of from the Gateway in compliance with planetary protection protocols.

Partnering with Industry for Technology Development

A key to assuring the CLPS and Artemis programs succeed will be NASA’s support of commercial companies. Several of the companies that will likely be involved in these programs were recently selected for partnerships with NASA centers. These partnerships open NASA’s expertise and facilities in the hopes of facilitating technologies the agency needs for future missions to deep space.

Render of Blue Origin’s Blue Moon lander executing a precise lunar landing – via Blue Origin

One of the big names involved in these partnerships is Blue Origin, which was selected for three partnerships with five NASA centers. The Johnson Space Center and Goddard Space Flight Center will work to mature a navigation and guidance system for precise lunar landings, a key requirement for the HLS.

Johnson and the Glenn Research Center will also work to mature fuel cells for Blue Origin’s Blue Moon lander, which is intended to be scaleable to both CLPS and HLS payload capacities. In order to develop propulsion for these landers, Blue Origin will also partner with the Marshall Space Flight Center and Langley Research Center to evaluate materials for liquid engine nozzles.

Another well heard of company partnering with NASA is SpaceX. They will be working with the Kennedy Space Center to model engine plume interactions with the lunar regolith, in order to facilitate landing large rockets vertically on the moon.

SpaceX is also partnering with the Glenn and Marshall centers to mature in-orbit propellant transfer technology for their Starship vehicle, a key technology for taking advantage of the launch system’s large payload capacity.

Render of SpaceX’s Starship on the lunar surface – via Elon Musk

Not only are the big “new space” companies getting involved. Three well-established aerospace companies are also taking advantage: Aerojet Rocketdyne, Lockheed Martin, and Sierra Nevada Corporation. Aerojet Rocketdyne will partner with NASA Marshall to design and manufacture a lightweight combustion chamber intended to reduce manufacturing costs.

Lockheed Martin, one of the nine CLPS providers, will partner with NASA Langley to test solid-state processed materials designed to improve spacecraft operating in high-temperature environments. Another partnership with Kennedy will test autonomous in-space plant growth systems, which could provide food and/or breathable air for long-duration human spaceflight.

Not all of the partnerships are limited to the moon, as some look forward to Mars missions. NASA Langley is partnering with Sierra Nevada Corporation to capture infrared imagery of their Dream Chaser cargo spacecraft, which is currently scheduled to make its first flight to the ISS no earlier than next year.

SNC will also work to mature a deployable decelerator for use in recovering the upper stage of a launch vehicle. This technology is likely similar to NASA’s Low Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) project, launching in 2022, which also has applications for entering Mars’s atmosphere.

Several other companies, including small businesses, will be partnering to develop various technologies in the areas of communications, materials, entry descent and landing (EDL), in-space manufacturing, and propulsion. NASA hopes these new technologies result in new commercial capabilities that the agency can utilize to achieve their deep space exploration goals at the Moon and Mars.

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