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Rocketdoc Notes – Week of April 18, 2020

Artemis Update

Last Friday NASA announced that Space-X had won the Human Landing System (HLS) Option A procurement. This has far reaching implications and I will summarize them in this blog.

The Artemis Program is the culmination of NASA’s recent planning for space exploration and has evolved over the last 23 years. The equipment previously developed and/or proposed for Artemis is shown in figure 1 below and is from reference 1, the official NASA website for the Artemis Program.

Figure 1 - Artemis Program as defined prior to April 15, 2021

These are all high price developments and have been soaking up NASA funding for last twenty years. However, as you will see this is about to change.

The goals of Artemis as quoted in reference 1 are given below.

During the Artemis program, NASA will land the first woman and first person of color on the Moon, using innovative technologies to explore more of the lunar surface than ever before. We will collaborate with our commercial and international partners and establish sustainable exploration for the first time. Then, we will use what we learn on and around the Moon to take the next giant leap – sending astronauts to Mars.

While the goals remain the same the proposed architecture has changed significantly if you read Reference 2, which is titled “Appendix H: the scoring results from the Next Space Technologies for Exploration Partnerships, Human Landing System, Option A”. This is the report from the team that scored the HLS Option A Proposals. The bottom line is that NASA driven by severe underfunding from Congress has decided to merge their Artemis Program with the on-going Space-X Mars Colonization initiative to increase the chances of success for both programs. HLS got only $850M in the 2021 NASA budget which is small in comparison to the budgets for SLS and Orion and not enough to fund a lander program in less than six years (see figure A-1 in the Appendix for NASA budget data).

In essence, Space-X will receive $2.86 B in government funding to modify several of their Starships to dock with the Orion capsule and/or the Gateway station and add enough extra DV so it can stop off at the Gateway’s rectilinear halo orbit as it travels to and from the lunar surface. Gateway Station is in a 3000 km by 70,000 km orbit with a twelve day period. These are not insignificant configuration changes and will result in a dedicated expendable HLS version of the Starship with unique development and production costs, which justifies the funding total.

The funding covers development and construction of the unique Lunar Lander versions of Starship plus the mission costs for the uncrewed demonstration landing and return plus the first crewed landing and return. I covered the development and operating costs of the Starship system in my October 18, 2020 Blog. In that blog I showed Starship is not optimal for lunar missions but offers a very low-cost lunar option once the basic two Starship stages are developed. That is the leverage Space-X included in their proposal and the plan that NASA bought into. NASA will only pay for the development and demonstration of the lunar-version of Starship and gets a lunar transportation system capable of landing 100 mT on the lunar surface for approximately $2,400/kg if all works as planned.

The HLS NASA is procuring is will be extremely cost effective but not even close to optimal from a launched mass perspective. Space-X will launch the NASA-unique version of Starship into LEO and launch five or six tanker versions of Starship one at a time to transfer propellants and fill the Lunar Lander Starship (LLS) with propellants. Space- X has not disclosed how they are going to transfer propellants in zero-gee but I suspect they will dock the Starships nose-to-nose and spin them to settle the propellants and allow transfer pumps to work. Once the tanks are full the LLS will burn out of LEO into Trans-Lunar Injection (TLI) orbit and depart for the moon. As it approaches the moon the LLS will do a second burn to inject itself in a near rectilinear halo orbit where it can rendezvous and dock with the Gateway Station. The LLS will then wait for the Orion crew transfer system to arrive. The Gateway Station is in a

After confirming the LLS is in place and operational NASA will launch the Orion crew transfer system using the Block I Space Launch System (SLS). The Orion will dock with either the LLS or the Gateway Station and transfer the crew. The LLS will then undock and preform the burn to intercept a low lunar orbit that flies over the lunar landing site (currently at the lunar south pole). After a coast to reach the right position the LLS performs the deorbit and landing burns and rests on the lunar surface. It appears the LLS will have two airlocks and a large elevator to ensure the astronauts don’t have to descend 30 m ladders to reach the surface. The elevator will also deliver oversized and overweight payloads to the surface. An artist’s rendition of the 2019 version of the LLS is shown as figure 2 below.

Figure 2 – 2019 Lunar Lander Starship (LLS) unloading a Lunar Rover

I have run the numbers to calculate how much payload the LLS can take to the lunar surface assuming it rendezvous twice with the gateway Station in Near Rectilinear Orbit to pick up and drop off astronauts. The DV to depart LEO, rendezvous, and dock with the Gateway Station, load two astronauts, depart the station, land at the Lunar South Pole, depart the South Pole and re-rendezvous with the Gateway station is 9256 m/sec. That is roughly equivalent to the DV required for a Single-Stage-to-Orbit (SSTO) and severely limits the LLS payload capability. It also means that the LLS is not a reusable system for the NASA Artemis HLS mission.

See figure 3 below to see Starship payload capability versus DV. This is actually Big Falcon Rocket (BFR) data published in 2014 but it should not be too far off. As you can see the BFR ran out of payload at about 9250 m/sec, so we have a problem. Space-X has addressed this by removing some inert weight, namely the features required to return to Earth, i.e., the reentry and landing Thermal Protection Systems (TPS) and the control surfaces.

Figure 3 – Big Falcon Rocket Payload versus Delta Velocity Curve

The 2020/2021 version of the LLS without TPS and control surfaces is shown in Figure 4 below. I don’t know the new payload capability, but it is probably relevant that the elevator is only carrying two astronauts. I suspect this configuration has a huge living space but only a few thousand kilograms of payload capability

Figure 4 – 2020 Version of LLS with no Earth Return Capability

The fastest way to increase payload capability to the moon is to transfer the astronauts from the Orion to the LLS while it is in Low Lunar Orbit (LLO) like we did during Apollo. We could then leave the lunar surface, transfer the astronauts back to the Orion in LLO, and leave the empty LLS in LLO. Unfortunately, the current Orion design doesn’t include enough propellant to get in and out of LLO and return to Earth (falls short of Apollo performance). If Orion could function like Apollo, we could bypass the Gateway Station and the DV saved (950 m/sec) would increase the payload to the lunar surface each mission by 27 mT. This is the difference between “Flags and Footprints” and a real lunar base. Note that an LLS on a one-way trip to the surface can deliver 100 mT and doesn’t need to rendezvous with the Gateway Station.

The Gateway Station has become a major international program (see figure 5 below) so NASA needs to walk a fine line to make both Artemis and the Gateway Station successful programs. The Landing Module in the picture will now be replaced by the Lunar Landing Starship.

Figure 5 – Gateway Station as described in the Daily Mail Newspaper

I am pumped by NASA’s decision to team with Space-X for the Artemis program. I think this will lead to earlier lunar bases and pave the way for Space-X’s Mars Program.

In the next blog, I will introduce you to the ideas behind the Book “Limits to Growth”, the affect it had on society back in the 1970s, and how the predictions in the book were eventually proved wrong. This is relevant because I believe the same processes will eventually reduce or eliminate the effects of Global Warming.

Thanks for reading.

Dana Andrews


Figure A-1 NASA 2021 Budget from Congress



2. Appendix H: Human Landing System, Option A

Next Space Technologies for Exploration

Partnerships-2 (NextSTEP-2)


National Aeronautics and Space Administration

April 16, 2021

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