But like all vehicles, they require propellant. And propellant is a very exorbitant commodity no matter where you are in the solar system. The vast majority of Skylon flights by this time will consist of fuel or the oxidizer necessary for lunar flights; however, this excessive pace cannot be maintain indefinitely.
Another source of propellant must be found.
Well, as luck would have it, there does indeed exist another source of propellant: the Moon! Specifically, in the crater known as Shackleton. The floor of the crater is in permanent shadow; the theory is that ice from comets that have impacted the crater over the eons have been preserved in this shadowy region.
All we have to do now is go get it. Of course, that proposition is fraught with complexity and a staggering power requirement. However, these barriers can be overcome.
The machinery necessary to produce lunar propellant should have the ability to:
- Break apart the lunar soil (regolith plus ice)
- Scoop lunar soil into a soil container
- Tow the container to a propellant station
- Extract the ice (water) from the lunar soil
- Extract Gaseous Hydrogen (GH2) and Gaseous Oxygen (GO2) from the water
- Liquify the GH2 and GO2 (LH2 and LO2)
This last stitch in the tapestry we have weaved so far will transform our species into one that can boast of dwellings and industry on other worlds.
(Note: Before we begin, the reader needs to know that this topic is the one that is most in flux, which is to say, it is changing as the technology changes. As such, this diary will be woefully lacking in specific details of our plan. But we will remain flexible and open-minded enough to adapt to whatever new and innovative technology exists by the time we are ready for this step in the space program. In the mean time, as is always the case, we present our current thinking with the knowledge that things can and will change in the future.)
Lunar Propellant Station (LPS)
The LPS will be assembled in the same way that the Lunar Surface Station (LSS) was assembled. Solar Power Stations (SPS) will provide continuous power to the LPS.
The LPS will consist of the following modules:
(2) - 4 kW - Soil Container Module (only 1 used at a time)
(1) - 1 kW - Ice Collector/Water Container
(1) - 104 kW - Water Electrolysis Module
(1) - 95 kW - GH2 to LH2 Module
(1) - 95 kW - GO2 to LO2 Module
Total Modules: 6
Total Power Requirement: 299 kW
Total Number of SPS: 24
Total Production: 1 LH2 Refill Tank plus 1 LO2 Refill Tank every 3 weeks
Since we will need approximately 6 refills every 3 weeks, we will need
6 LPSs: Total Modules: 36
Total Power Requirement: 1,792 kW (1.8 mW)
Total Number of SPS: 144
Total Production: 6 LH2 Refill Tank plus 6 LO2 Refill Tanks every 21 days
This will provide us with enough propellant to refill a Lunar Transfer Vehicle (LTV) and the OTV Landers that will carry the propellant to the LTV in Lunar Polar Orbit every 21 days.
Soil Container Module (SCM)
The SCM is simply a hollow Skylon module with the top open so that lunar material can be placed inside. The bottom has a door that opens so that the container can be emptied. The SCM is also lined with small microwave ovens.
The crane from a Utility Lunar Roving Vehicle (LRV) is used to place the SCM on the Lunar Payload Carrier (LPC).
The SCM is then towed to a soil collection area, where another Utility LRV awaits its arrival. That Utility LRV uses the bulldozer blade to scoop lunar material up and into the SCM.
When the SCM is full, it is then towed to the LPS and connected to the Ice Collector. A hood is placed over the opening of the SCM.
Microwave energy is applied to the SCM, heating the regolith and ice. The ice, instead of turning to water, turns directly into vapor (sublimation). The vapor is then collected in a container in the Ice Collector module (we are assuming a high rate of capture with this technique; however, we also understand that this may not be true, and so are always on the look out for a better way).
But because the vapor resides in a vacuum (along with the frigid temperatures), instead of turning into water, it turns back to ice! We will be employing a technique called a "Cold Trap" to recover the lunar ice.
Once the ice has been extracted, the SCM is disconnected and towed to an area away from the LPS. There, another Utility LRV picks up the SCM from the LPC and swings it around so that the bottom can open up, spilling its contents. The SCM is cleaned and inspected, and the bottom doors are closed. The SCM is then loaded back onto the LPC and towed back to the soil collection area. Lather. Rinse. Repeat.
Meanwhile, back at the LPS, the block of ice that had been captured gets moved to the 2nd half of the Ice Collector/Water Container Module. The ice is sealed and melted to produce water at an appropriate air pressure and temperature.
An anode and a cathode is placed in the water, and electricity is applied (electrolysis). GH2 will appear on the cathode, while GO2 will appear at the anode. The GH2 and GO2 are collected and stored in an adjoining module.
Once the GH2 and GO2 have been stored, the process of liquifying can begin. When this stage of the process has been completed, LH2 and LO2 is produced, and stored in the Refill Tanks. Once the Refill Tanks are full, they are towed to an OTV Lander, where it is either carried aloft to refill the LTV in polar orbit, or used to refill the tanks of the OTV Lander itself.
We can see what the LPS looks like:
The top module is the SCM. Beneath it is the Ice Collector/Water Container Module. Below that is the Water Electrolysis Module. To the right is the LH2 Generator Module, and to the left is the LO2 Generator Module. Refill tanks are used as reservoirs to store the liquid propellant.
We have seen how easy it is on one hand to mine the moon for lunar propellant. However, the staggering amount of energy to produce said propellant does appear daunting. Because of our capability for reuse and commonality, SPSs can be set up easily and in large numbers. Without this capability, cracking lunar water would be nearly impossible.
Regardless of which technology is ultimately used, the end result is still the same: we can go bragging that we are now a species of outer space.
Now, being part of the reality-based community, we understand one of the most fundamental equations in all of rocketry: the funding equation. It seems that this equation is always a stumbling block to a robust and vibrant space program.
We believe that we have adequately solved the funding equation. However, the solution does have the distinction of being, shall we say, eccentric. Regardless of how it is perceived, we feel that it solves the equation sufficiently.
Of course, that's a story for another day.
On a personal note, I would like to give a shout-out to my friend and our very own Dr. Rich Holtzin, who yesterday penned his very first diary on Daily Kos that went straight to the Community Spotlight and the Recommended List!! I am so happy that the DKos community got to meet this amazing person whose sincerity, integrity, enthusiasm, and depth of knowledge really came through in his well-written and thoughtful post. He is the reason NMSTARG exists at all. A man of many talents. Thanks, Rich! And a genuine, heartfelt congratulations on a first DKos diary well done!