Here are newest screenshots from my video, showing a viable (maybe the only viable) on-orbit refueling idea for a @SpaceX Starship or HLS. The video works best on a large screen. Let me know what you think about it. claude.ai/artifact/XjNotnzNa… @elonmusk @larsblackmore @NASAAdmin @MarcusHouse @InfographicTony @LunarCaveman @mcrs987 @DJSnM @CrainTim @Erdayastronaut

Here’s a money shot for all the CAD guys. @mcrs987 @InfographicTony

This configuration is not going to work. The depot and HLS lander will have to be mated nose to nose and rotate end over end (cartwheel) during fuel transfer. It is the only way to prevent gas and liquid phases of the propellants from mixing together and destroying the pumps. While cartwheeling in LEO, the gas will move to the center of rotation (top of tanks) and the liquid will move to the bottom of the tanks, where it belongs. The nose to nose configuration also will save RCS and ullage gas mass. The only added mass I see is additional transfer lines. We were supposed to have proof of concept by now. @SpaceX is way behind schedule proving on-orbit cryogenic fuel transfer is viable.

Recap: Tugs will enable 50% more landed mass on the lunar surface compared to sending lunar landers directly on a Trans-Lunar Injection (TLI) trajectory. The general concept is straightforward: a tug and lunar lander are launched together as a stack into Low Earth Orbit (LEO). The current Falcon Heavy limit in partially expendable mode is 57 metric tons (MT), and landed lunar mass scales directly with LEO launch capacity. Once in orbit, the tug performs TLI and Lunar Orbit Insertion (LOI). After separation, the lander remains in a circular Low Lunar Orbit (LLO) until it is commanded to descend, while the tug executes a Trans-Earth Injection (TEI) and uses aerobraking to reenter LEO. I also have concepts for a reusable heat shield that would allow the same tug to make multiple round trips between LEO and LLO. This architecture would require on-orbit refueling with liquid hydrogen (LH₂) and a Nuclear Thermal Propulsion (NTP) engine on the tug. I assumed an Isp of 800 s for the tug and 350 s for the lander. All of the required technologies either already exist or are just over the horizon. Overall, tugs would dramatically accelerate the buildout of lunar infrastructure compared to traditional approaches. Background: Before Nixon's OMB killed the program in January 1973, @NASA had a nuclear rocket engine research program at Plum Brook Station (PBS) in Sandusky, OH. Their hot-fire test facility was located at the Nuclear Rocket Development Station (NRDS) in Jackass Flats, NV. They learned a lot about nuclear rocket propulsion from 1961 to 1972. They had fires and explosions along the way but managed to build several different engines. These included the Kiwi, Phoebus, and NERVA variants. The best one they produced, IMO, was the NERVA XE. It had an Isp of 811 s, a maximum thrust of 75,000 lbf, and a best thrust-to-weight ratio (TWR) of about four. Project Timberwind / SNTP (Space Nuclear Thermal Propulsion) developed in late 80's and early 90's under the SDI promised a TWR of around thirty. The most recent design, by @DARPA program Demonstration Rocket for Agile Cislunar Operations (DRACO 2020-2025) was just recently cancelled. The TWR for DRACO was much lower than previous designs because they used a significantly lower enrichment of the U235. They improved the materials science but shot themselves in the foot by switching from HEU to LEU. The earlier programs had used HEU and were showing real progress over time. We gave up too soon on NTP in favor of NEP. NEP just does not have the thrust we need for deep space exploration and colonization! 🇺🇸 🚀 🦾 @NASAAdmin @CrainTim @Jason_Lil_Kim @astrobotic @blueorigin @SpaceX

Happy Memorial Day!

There are more advantages to locating the first human colonies on the Hellas Planitia. Here’s one advantage that @elonmusk will appreciate. The Hellas Planitia is literally the best place on the entire planet to make CH4. The air is twice as dense there as it is on Arcadia Planitia. A Sabatier reactor requires 1 to 3 bar of internal pressure to work properly and it generates a lot of heat while it is working. CO2(g) + 4H2(g) + 30 kJ/mol [Startup Heat] --(Ni(s) catalyst)--> CH4(g) + 2H2O(g) + 195 kJ/mol [Total Heat Evolved] By locating CH4 production on the floor of Hellas Planitia, you basically cut in half the hardware mass required to feed the Sabatier reactor. You only need roughly half the volume of Martian atmosphere feeding the reactor on Hellas Planitia that you would need on Arcadia Planitia. Intake fans and piping mass is reduced dramatically. The thicker air on Hellas Planitia will aid with convective cooling of the Sabatier reactor vessel if needed. The waste heat evolved during the reaction could also be used to heat the habitats/work areas in the colony. There is a potential problem with using unfiltered Mars atmosphere to feed the reactor. There are small amounts of sulfates and perchlorates in the Martian air. Sulfur will poison the Ni catalyst and Cl will combine with H to form HCl. HCl will attack and pit the steel components of the reactor. A 3-stage chemical guard should solve the problem. Use a vortex to spin out all but sub-micron size dust particles. Then use HEPA/ULPA filters to remove the rest of the dust. Finally, use a sorbent bed of activated carbon to remove the unwanted chemicals. A zinc oxide ‘polisher’ sorbent bed could be added to remove any sulfur remaining. This is just another reason to build on Hellas Planitia! @NASAAdmin @SpaceX  

I am concerned about NASA’s current timeline for Artemis. I don’t see how @SpaceX can possibly be ready with the HLS spacecraft for orbital testing before the end of 2027. At this point, @blueorigin is the only company that has a realistic chance of being ready by the current scheduled Artemis III launch date of late 2027. One requirement that @NASA insists on–and rightfully so–is the ability for the HLS pilot to take manual control of the spacecraft if the software is guiding it towards an unsafe landing. This exact capability is what saved Apollo 11. To the best of my knowledge, SpaceX has not planned to enable any type of manual control of HLS during the lunar landing phase. An automated landing system has served SpaceX well on concrete pads and drone ships, here on Earth, but carries too many risks to ever be human-rated for making lunar landings, without a manual override system being available. @NASAAdmin

My favorite photo from Artemis II misson.

Here's one last photo showing a close-up of a random landing site in this area. The blue circle at the center of photo is 12 m in diameter.

The larger circle is about 2 km in diameter. The small blue circle in top left quadrant is 12 m in diameter. I was able to place the small circle in numerous places without encountering craters or boulders. Not sure what @SpaceX HLS landing gear diameter is, but the @blueorigin lander would fit inside the 12 m diameter circle.