FOLDINGSS

Keep in mind that the ship needs to hold all the resources necessary for a 900 day journey. This means all the food, all the water, all the gases, all the propellant, all the fuel, all repair parts, all scientific requirements, everything for the 900 day mission. This requires a large storage area. Recycling will go a long way to reducing the storage space needed, but there is no way around the need for a large ship.

1. After our successes with Apollo, humanity was comfortable with the assumption that humans could live in micro gravity for extended periods of time with little negative effects. Our experience on the ISS since then have shown that there are many health problems that come with the absence of gravity. Problems with bone density, muscle density, vision, digestion, and other systems become big problems when living in micro gravity for months. So 8, 10 months in micro gravity may simply be too hard on the human body to survive or to accomplish a deep space mission. Some are now considering long term habitation on Mars or Luna without any study of the effects of 1/3 or 1/6 Earth gravity. Again, our assumptions may prove completely wrong.
2. The ISS program demonstrated that we can build long lasting structures in space. One of the great innovations of the ISS program is the humble Common Berthing Mechanism (CBM). This standardized apparatus for connecting modules for both structural connection and environmental envelope connection has proven very effective for in-orbit integration. Its passage dimensions are small, but suits the current boosters nicely in terms of the maximum size of modules we can currently place in orbit.
3. The ISS has demonstrated long term water and air recycling systems. This technology dramatically reduces the mass of supplies required for crew life support on long duration missions.
4. ION drive has just within the last 5 years reached the power levels where large ships can utilize them. The advancements have come in two areas: First, the thrusters have become more powerful, like the X3 multi-channel Hall thruster. The power levels of this unit on the order of 10N is small but sufficient for orbital drives. Second, the solar collection methods have advanced to the point that thrusters like the X3, which need tens of kilowatts are practical. Modern multi-junction cells have reduced the collection area to a point that it is practical to build solar collectors to power electric ION drives to reach destinations within the inner 4 planets.
5. The innovation of reusable boosters has put the economic and political cost of this type of program with reach of a single political (US 4 or 8 year) cycle.

The Earth to Mars Plan put forth by NASA in 2016 based on 2010 space proposal layed out a 4 step plan:
0) Use the ISS to learn about long term habitation in space
1) Cis Lunar deep space gateway (Build gateway in orbit around moon, build a moon base for DST)
2) Assemble Deep Space Transport ship (DST) in lunar orbit with support from moon base.
3) Mission to Mars on DST
4) Landings on Mars from DST cis Mars.

The FOLDINGSS mission is first and foremost a deep space research station that may or may not ever journey to Mars. However, it builds upon the knowledge gained and the techniques used on the ISS. Specifically, the ISS effort has yielded two major outcomes as it pertains to FOLDINGSS. First, it has demonstrated that mirco gravity is a huge problem for long term human occupation in space. Second, it has shown the success of the CBM (common berthing mechanism) as a means to integrate large structures in space. Other matters relating to life support, like water recycling, have been furthered by the ISS experience as well. So in terms of item 0, FOLDINGSS is very similar to the NASA plan.

FOLDINGSS assumes there is very little actual value in a moon base. Nor does it find any value in a small Lunar space station. The FOLDINGSS research vessel meets all the criteria of the DST and may eventually fulfill an interplanetary role, but, rather than expending time and money on Lunar infrastructure. FOLDINGSS builds a ship in Earth orbit and bases all its activities from LEO support. Ironically, the FOLDINGSS research craft can very easily act as a transport mechanism to Lunar orbit if there are concurrent programs that can benefit, but ultimately Luna is not a fundamental aspect to the FOLDINGSS program.

FOLDINGSS primary mission terminates after a successful 900 day deep space demonstration. However, Items 3 and 4 or the NASA plan can easily be accomplished by having the FOLDINGSS craft act as the DST. It could journey to Mars to perform functions from orbit, such as real-time robotic control and science. It could also work with a robotic lander and ascent vehicle for sample return. And finally, the FOLDINGSS version of DST could be the launching point for a human Mars lander and ascent vehicle. Since FOLDINGSS would be in Mars' orbit, relatively smaller vehicles could be used with less energetic ERL profiles for a martian landing. One journey to Mars could potentially support multiple sorties to the surface especially if in situ fuel production was possible on the martian surface.

1) The Starship vehicle was designed as a direct return vehicle. That is to say, it must fulfill the final leg of a return trip from the martian  surface. So, assuming it is completely refueled on Mars, it has to be big enough to hold enough fuel and oxidizer to ascend from Mars. It also has to carry enough supplies to support the returning crew compliment for the duration of the trip back to Earth. After reaching Mars orbit it must enter a trans-earth trajectory, perform the necessary transfer burns to reach Earth. Once it reaches Earth, it will not attempt to orbit Earth, rather it will use its heat tiles to accomplish a high energy entry into Earth's atmosphere, where it will use aerodynamics to slow further and navigate to a landing position, where it will use its remaining fuel to accomplish a propulsive landing.
2) The Starship vehicle will reach Mars from LEO after Earth rendezvous with 5 or more like vehicles for LEO refueling. The 3 vacuum engines of Starship will place it in a trans-Mars trajectory and execute all transfer burns to get it to Mars. It will not attempt to orbit Mars but will use its heat tiles to accomplish a high energy ERL using the Martian atmosphere for interplanetary velocity braking.
3) The Starship vehicle is boosted to LEO by the Starship Super Heavy booster. As multiple boosts are required to refuel the Starship which will travel to mars, at least one additional Starship is required, and most likely several additional Starship tankers and Starship Super Heavy boosters will be required to get the fueling accomplished as quickly as possible.

FOLDINGSS approaches the Mars transit problem from a different perspective. FOLDINGSS will accomplish a similar outline in this way, made possible by the relatively high specific impulse made possible by electric propulsion.

1) A FOLDINGSS lander/ascent vehicle (most likely a large capsule with a single piece heat shield and landing gear) would blast off from the surface of Mars and rendezvous with the FOLDINGSS research ship in low Mars orbit (LMO). The FOLDINGSS research ship will have been in orbit since arriving at Mars at the previous earth-mars conjunction. The FOLDINGSS will have an abundance of ION propellant for the return trip remaining from its initial fueling in LEO. The FOLDINGSS will execute one small chemical rocket burn to begin a series of orbit modifications to make the orbit of Mars more and more elliptical. At some point, the mars orbit will intersect with an elliptical orbit of Earth and an additional thrust will be applied to cause the FOLDINGSS ship to be captured by Earth's gravity. ION burns will then be used to circularize the Earth orbit until FOLDINGSS is in LEO. The FOLDINGSS ship will rendezvous with one or more Earth rated return capsule (likely a Crew Dragon capsule) and return the martian crew and samples to Earth. The FOLDINGSS ship is then ready for re-supply for subsequent interplanetary missions.
2) The FOLDINGSS ship reached Mars initially by leaving LEO fully fueled and supplied by multiple Falcon Heavy launches or Delta IV heavy launches. The crew was rotated by Falcon 9 crew flights as well. Refurbishment of the Mars Landers is accomplished in LEO by replacement of the one piece heat shield and LEO refueling. The FOLDINGSS craft leaves Earth orbit with a small chemical burn and then uses ION drive to modify its orbit to be more and more elliptical. Eventually, by virtue of Mars passing into position and the elongation of the orbit, FOLDINGSS orbit will intersect with an extreme elliptical orbit of Mars, at this point additional chemical and ION burns are performed so that Mars captures the FOLDINGSS craft. ION propulsion is used to circularize the orbit of FOLDINGSS around mars until it is in LMO. By using ION thrusters, even a huge ship like FOLDINGSS can reach mars with enough propellant for a return trip with no additional refueling. Further, by trading transit time for relative comfort the energy of the landings on either Earth or Mars is reduced to that of low orbit entry. Since FOLDINGSS has constant inertial gravity, crew health can be maintained for a marginally longer transit and orbit stay. Radiation is still a problem, but is addressed through more extensive shielding and medical interventions. In whole, the risk to mission and crew is greatly reduced for the FOLDINGSS approach.
3) The FOLDINGSS craft was assembled in LEO in similar manner to the ISS, making extensive use of CBM style interconnects. Even the ION engines and Chemical engines on the ISS are modular and attach with CBM type connections. This allows the ship to be used on dozens, if not more, missions. To prepare for any single mission, the long duration trip requires life support supplies, ION propellant, Chemical Fuel and Oxidizer, crew, and mission specific hardware. All these are delivered via 5m or 7m diameter rockets such as Falcon Heavy or Delta IV heavy or Vulcan. These use traditional chemical rocket boosters with the hope that reusable portions drastically reduces mission costs.

Once the habitat is spinning, it will remain spinning until the spacecraft is retired. So, to accomplish moving the ship and docking, the most reasonable approach is to have a connected second part of the ship which does not spin. This second section, which we call the drive section, must be connected to the spinning habitat via some sort of bearing. The obvious connection points are the center of the spinning habitat, like an axle or the perimeter of the habitat like a handle riding on a perimeter rail. This proposal chooses the axle connection point.

Likewise, if it is postulated that the habitat will always be spinning and therefore always have an acceleration toward the outer perimeter of the wheel, many simplifications are possible with the build out of the habitat. Sanitation, food preparation facilities, living quarters, fluid systems, gas systems, all these can benefit from an assumed constant direction of gravitational acceleration.

These two requirements eliminate any sort of sealed bearing system. It is beyond our current technical capabilities to produce a resilient seal that can operate in the environment of space that is both an exceptional gas seal and long lasting. For this reason, the proposed FOLDINGSS spacecraft has separate envelopes and access between the different sections is only possible through a special airlock that can dock to either the spatially fixed drive sections or spin and translate to dock to the spinning habitat section. This mechanism is called the Angular Transfer Structure (ATS). This mechanism allows FOLDINGSS to have a heavy robust bearing mechanism, have independent but well sealed envelopes and still allow the transfer of cargo and crew between the ships sections as needed (albeit a bit a slow and cumbersome transfer method). 

The ability to loft modules with this type of interior space is a major benefit for the program and speeds the creation of a capable ship by at least a factor of two.

The ship will have a weight of 500,000 lbs. That means, on Earth, 500,000 lbs of thrust are required to hover. The FOLDINGSS ship has a tiny fraction of that thrust. At full power, the ship can only produce about 162 lbs of thrust. This is sufficient for low impulse orbital changes, but is a couple thousand times too weak to even hover on earth. On the moon, there is no atmosphere, but the thrust required to hover is still over 90,000 lbs. On Mars, 180,000 lbs would be required to hover.

Realistically, Earth's moon might make a reasonable setting for constructing spacecraft from scratch. There is even a lot of resource there already. However, for the near future, the only flight ready construction methods available are those pioneered for the ISS. The Common Berthing Mechanism is a time proven method for both structurally attaching pre-built modules and sealing their connection, all with captured, self contained fasteners. Thus, the FOLDINGSS craft is a structure that is bolted together at CBM interfaces. Each module must be small enough to be boosted into orbit by available boosters.

Now an ION thruster is a completely different beast. First, it works by using a high voltage electric field to accelerate propellant ions (usually a noble gas ion, like argon, or xenon) to very high speed. This means it can achieve a propellant mass efficiency resulting in specific impulses of 2000 to 5000 seconds. This means 1/5 to 1/15th the propellant mass. There are two catches, though. First, current technology has only been able to produce ION thrusters capable of 5.4N of thrust (for comparison, the tiny Draco thrusters on the Dragon capsule produce 360N of thrust). Second, the power for creating this thrust does not come from the propellant, unlike chemical rockets. The X3 thruster which set the 5.4N thrust record, build by the University of Michigan, requires 200 kW of electrical power.

Given the proposed size of the FOLDINGSS craft (500,000lbs or 227mT), two X3 type thrusters built for long life, and powered by triple junction solar arrays, could just barely supply the required delta-V for a Mars Orbital transfer over an 8 month period. The calculated mass of propellant would be on the range of 17,600 lbs (8mT). Though this transfer takes longer and is less efficient, it can be supported within the mass budget of the ship will place large stresses on the structure of the ship.

The second reason for chemical thrusters is safety. The ION drives are a novel technology. It will be nice to know there is another means to get home if the ION drives fail and cannot be repaired. The chemical thrusters will not have enough fuel to accomplish a complete mission, alone. However, the strategic use of fuel for bumps of impulse should leave enough fuel to effect an elliptical orbit to return the spacecraft to a perigee close to Earth orbit. The capsules could then likely still effect a harrowing return to Earth, if needed in an emergency.

1. Breathable Air, so sufficient Oxygen partial pressure and acceptable levels of CO2 and other toxins. For long duration trips, this means gas recycling.
2. Air pressure to keep things that should stay liquid, as liquid within our bodies.
3. Heat or cooling to keep the interior of the habitat compatible with the temperature range humans can survive.
4. Drinkable water. Humans need a lot of water, for any long duration away from an external supply, this means water recycling.
5. Food and the requisite food storage and preparation. Fortunately, humans don't require a lot of food. Dehydrated foods are relatively light and compact. Probably there will be little food production on board, though there will certainly be experiments with horticulture and the breeding of chickens and small mammals.

This means a human cannot live on the surface without a pressure suit, full breathing gas support, and supplemental heating. Radiation does not kill immediately, but the increased dose over time will certainly induce many cancers and other conditions associated with radiation exposure, so life expectancy will be much lower unless some radiation shielding is provided, possibly by underground living.

The lower solar flux means there is insufficient light for traditional earth crops without additional UV light is supplied artificially. Additionally, plants will need more pressure, heat, liquid water and CO2 to thrive on Mars.

Several of the threats mentioned above can be mitigated with energy. There are no known hydrocarbon sources on Mars. Solar flux is too low for much solar energy collection without huge arrays or some sort of solar concentration.  Martian windmills are insufficient because of the low density of the atmosphere. This leaves nuclear energy as about the only viable energy source on Mars.

The biggest question, for which we have no easy answer, is whether the reduced gravity will have an adverse effect on human health. There are really only two ways to get this data. First, we can put humans on Mars. Assuming all the above can be overcome, we do the minimum 2.5 year study to see what happens. Or, we can use a ship like FOLDINGSS to simulate Mars gravity in a much more controlled environment at a much safer distance from Earth.

A dense atmosphere would capture more heat, possibly to the point of thawing some of the water buried in Martian soils. Enough atmospheric pressure could likely be achieved to eliminate the need for pressure suits for humans on the surface of Mars. Breathing apparatus will still be required. The artificial magnetic shield would also reduce solar radiation and the increased atmospheric density would decrease primary cosmic rays significantly, though probably not eliminate secondary cosmic rays.

If enough plant life could be supported, through the use of special low light plants or artificial lighting, O2 could be generated into the atmosphere as well through photosynthesis. Thus, over a long period of time it could become possible for humans to walk the surface of Mars without pressure suits or breathing support.

All of this assumes a great many things. Things having to do with plant life and the success of an artificial magnetic field. None of these steps will increase the gravitational acceleration of Mars, however.

So, the point is that the size of the individual pieces of the FOLDINGSS ship are already near the maximum size of current boost vehicles. New Glenn, or Vulcan boosters would have ample fairing enclosure assuming they become operational anytime soon. Likewise SLS will eventually have a variant with the capacity but these last three launch vehicles are still under development and the track record for these things getting finished in a timely manner is very dismal.

All these rockets are performing a much bigger service than just lifting pieces of the ship into space, however. The are providing the lions share of the delta-V for these missions. Most of the energy required to get to Mars, Deep space, or even Luna is just the energy to get ships to orbital height and to accelerate them to orbital velocity speeding around the Earth. So, even though it seems like boosting parts into space is sort of a waste of time and energy, it is actually a very necessary element to the journey. An added bonus is that, that energy is sort of conserved as the FOLDINGSS ship goes about its many missions. That boosting energy doesn't need to be spent again. Smaller rockets just lifting crew and supplies is all that is required for subsequent missions regardless of the FOLDINGSS ship's destination.

Humans and virtually all life on Earth competes for almost everything. Human's did not invent this dynamic. However, humans have certainly added many new dimensions to this competition within our species. We compete for mating rights, for education, for money and therefore housing, employment opportunities, food, recreation and so on. In fact, humanities entire existence is based upon competition. Some forms of this competition benefits society as a whole, other forms of the competition are very destructive. Wars would be an example of a destructive competition. Sports would be an example of a competition that has some benefits in terms of fitness, but that consumes a huge amount of resources and pays back very little in terms of actual useful social advancement.

Competition in terms of exploration has had a mixed bag. Specifically, it has been great for the societies doing the exploring and it has been disastrous for indigenous inhabitants of the lands being explored, most often.

The exploration of space has probably been one of the most benign forms of exploration humanity has ever embarked upon. As far as we know, there have been no indigenous inhabitants of the "lands" we are exploring. It has caused the creation of many useful technologies. It likely prevented a war between the west and the soviets in the 50s, 60, and 70s. It is even amazingly affordable. If a person were to add up all the money spent on little league sports, sports arenas, sports television broadcasting, sports merchandising, you would likely find more is spent on that competitive endeavor that the U.S. space program per year. Oh, and it has yields satellites to aid in our entertainment pursuits as well.

Besides the relative low cost of space exploration ( approximately $100 annually for every person in the U.S. ), much of that money provides useful technology or capability that the U.S. military would or already does cover in its, budget. So, the reality is that the civilian space program is almost free.

So the space program is a means by which nations and individuals can challenge themselves and in the process get rewards of scientific and engineering advancement. There stands a very good chance that space research will pay dividends either by advanced warning of space catastrophe or even the ability to prevent them. It is also likely that space exploration will allow humanity to survive some Earth based catastrophe in the future by virtue of humanity existing on other planets or objects within our solar system.