I was going to write about China and their space solar power plans in reply to a comment by Barry. Then…I began to think about future launch vehicles and spacecraft in general and decided to write specifically about spaceships. Sorry Barry. I have touched on the various elements involved in spaceflight in other posts but I will here attempt to review and clarify.
The first issue is defining “space” which is not really 200 miles up. Space begins more accurately a couple orders of magnitude higher than Low Earth Orbit (LEO) and should be demarcated at 22,236 miles (Geostationary Earth Orbit or GEO). There are several reasons to call anything below this minimum distance above sea level “Earth Orbit” and refrain from calling it space. A simple simile explains why: Low Earth Orbit has as much in common with deep space as a duck pond has with the North Atlantic. The radiation environment in deep space necessitates a massive cosmic ray shield for any long duration human missions. Even the next order of magnitude quarter million mile wide region of space between GEO and the Moon is best characterized as a minor “Cislunar Sea.” While Earth orbits are delineated into many different paths, for simplicity let us say there is only LEO, which is everything below GEO. Following this line of reasoning Human Space Flight (HSF) should not include going in endless circles at very high altitude in LEO and this activity should thus be called “Orbital Flight.” HSF should rightly be minimally defined as transiting between GEO to the Moon across the Cislunar Sea using the blanket term “Human Space Flight Beyond Earth Orbit (HSF-BEO).” The ice at the Lunar South Pole is the key to building any true spaceship as well over a thousand tons of water will be required for each shield. Water can be lifted from the Moon using 23 times less energy than from Earth for a given mass.
Now comes the second issue of classifying “spacecraft” and “spaceships” as two very different vehicles. In regards to the Cislunar Sea this can be slightly confusing as a Lunar Cycler might possibly have all the attributes of a true spaceship except for a lack of nuclear propulsion. If the Cycler meeting the other criteria is designed with the capability to mate with a nuclear propulsion module and undertake deep space missions it can then be called a spaceship even if it is limited to the Cislunar Sea. A true spaceship must have a Near-Sea-Level-Radiation-One-Gravity environment (NSLR1G). The two systems necessary for generating this environment are a massive cosmic-ray-water-shield (CRWS) and tether-generated-artificial-gravity (TGAG). The first destination for Human Space Flight Beyond Earth and Lunar Orbit (HSF-BELO) missions is not Mars, it is Ceres in the asteroid belt. Mars is a dead end. Such a mission to Ceres, using a Medusa “soft” nuclear pulse propulsion (NPP-1, first generation) drive utilizing low power fission bombs, would require at least a year and more likely two. Thus, a true spaceship would require living space large enough to meet the psychological requirements of the crew, a closed loop life support system (CLLS) with multi-year endurance, the already mentioned massive cosmic ray water shield and a tether-generated artificial gravity system.
To go beyond Ceres to the ocean moons of the gas and ice giants, starting with Callisto outside the Jovian radiation belts, will require more than a soft fission pulse propulsion system. Callisto bound spaceships will require a second generation hard fusion pulse propulsion system utilizing a multi-thousand ton alloy disc from a lunar factory. (Callisto: CRWS/TGAG=NSLR1G+NPP2+CLLS=HSF-BELO)
Those lunar factories mass-producing multi-thousand ton alloy discs will take several decades to construct and no “Orion” second generation fusion bomb driven spaceships are likely to appear for a half a century or more. In the immediate future the prerequisite for a first generation spaceship fleet construction pipeline is the creation of a Cislunar Infrastructure and the fundamental building block has yet to appear. The most critical piece of the puzzle is a construct I have written about previously on this blog: “The Fat Workshop.” How much interior space will be needed to keep a small crew psychologically healthy for two or three year missions? And how small a crew?
To send a 60 foot diameter double-hulled Fat Workshop to the Moon is going to require a much larger iteration of the SLS. The most efficient configuration of the ideal Super Heavy Lift Vehicle (SHLV) may turn out to be a reusable first stage in the 10 million pound thrust range with 4 large 2 million pound plus thrust outboard engines and one smaller central landing engine. Whether the second stage would land back in it’s entirety or just the engine module remains to be seen. It would seem the laws of thermodynamics and the rocket equation demand the sacrifice of at least the second stage propellant tanks, as was the case with the space shuttle.
Not only the workshop but likely a semi-expendable Robot Lander will usually top these SHLV lunar missions to develop infrastructure. The Landers will land on ice deposits and bring water up to the workshops in orbit around the Moon. The wet workshop crew compartment will be the fundamental building block as it will serve as a crew compartment for first Low Lunar Frozen Orbit (LLFO) space stations and then be used for both a Lunar Cycler fleet and a network of crewed GEO telecom platforms. Once the pipeline is supporting these assets in the vicinity of the Moon, transiting between the Earth and Moon, and in high orbit around the Earth, then NPP1 modules will effect the first true spaceships.
- Earth Orbit and Orbital Flight (not space and space flight).
- HSF-BEO (beyond GEO and across the Cislunar Sea to the Moon).
- Low Lunar Frozen Orbit (LLFO).
- Cosmic Ray Water Shield (CRWS using lunar water brought up by Robot Landers).
- Tether Generated Artificial Gravity (TGAG).
- Near Sea Level Radiation One Gravity (NSLR1G environment).
- Closed Loop Life Support (CLLS multi-year endurance utilizing the CRWS as a grow medium for a self-sustaining ecosystem).
- Medusa soft 1st generation fission Nuclear Pulse Propulsion (NPP1).
- HSF-BELO (beyond lunar orbit to Ceres as the first destination).
- Orion 2nd generation alloy disc fusion Nuclear Pulse Propulsion (NPP2) to Callisto.