Wednesday, June 4, 2014

From the Earth to Mars and Back Again.

Strap motors on it and send it off to Mars.

Louis Shalako

It was recently announced that Russia is no longer interested in supporting the International Space Station, preferring to focus on paying launches perhaps. There’s little doubt it is a pressure tactic in the political arena, where the U.S. and Russia stand poised on the brink of another cynical and not-very-friendly non-war.

(Talks are back on again. – ed.)

If the U.S. and its partners can’t find additional funding, the station could be abandoned (or at least no longer under development) by the year 2020. Every such system or machine has its natural life. It can’t stay up there forever in any case.

Big question then is; what do they do with it?

My suggestion is to strap motors on it, slap on a couple of bipropellant fuel tanks, and shoot it off to Mars orbit using both autonomous and telemetric control systems.

Four small steerable motors, off-the-shelf if possible, are enough for a slow acceleration as well as steering and control. The rickety old thing isn’t designed to take a lot of gees, and in fact some systems, like the solar panels, will probably have to be demounted and rigged for safe storage. If it takes all day to get her up to a plausible ‘X’ m/s Delta-V, no big deal. Using a simple Hohman transfer at opposition, it’s not necessary to make the shortest possible trip because it’s un-manned. We don’t have to worry about a human crew, considering the long-term effects of zero gravity, cosmic rays and solar flares, and including ‘social and psychological factors.’ Psychological factors come into play on extended, multi-year missions.

But, it basically represents an exercise in getting a large package into a stable Mars orbit, and it represents assets in situ for a series of eventual manned Mars surface missions.*

It represents a livable habitat where stores, life-support and backup systems are already operative. You don't have to land on the Martian surface and start setting things up. It’s a place to mount the latest in cameras and sensors, and other equipment. It’s an LMO observatory. In the meantime, waiting for a human crew, NASA is constantly monitoring the system and its components. Changes in the Martian surface can be monitored over the long term. This includes weather observation, one of the keys to a successful surface landing and return.

The next phase of the mission is to send off further habitat modules, oxygen and fuel tanks, a simple pair of highly-upgraded, new type of landers, additional resources, and other necessary equipment (including nuclear power generators) to orbit the planet separately in a planned configuration, one designed for easy recovery. Each of these assets would retain some small reserve fuel/maneuvering capacity aboard the transit package. They have the ability to maneuver in orbit for eventual rendezvous and recovery. The landers, once unleashed from their transit cocoons, would use autonomic systems to dock with the space station for eventual use. Even the cocoons** could be reusable, if nothing else as a supply of refined metal for on the spot fabrications.

The landers themselves, unlike the Lunar lander, would be more versatile in that they could deliver a tracked robotic vehicle to the surface just as well as a human crew. In the Lunar phase, only the manned pod left the surface. The new landers are also a return vehicle, and have a desirable ability to return on their own as reusable machines. They’re not abandoned on the surface, but then they don’t have to be—there’s a surplus of fuel a hundred and forty or so kilometres above the surface in the Mars Station stocks. The landers are designed to go back and forth. The surplus fuel stocks are the Delta-V budget for exploration.

Manned missions from Earth to the Mars station would carry the minimum of supplies and equipment, which means less mass. Less mass per mission/shot means more fuel available for speed, i.e. shorter transit times. This is only possible if a multi-year supply of oxygen, water, food, batteries and bulbs, materials, tools and wrenches, socks and underwear, everything our astronauts might need, is already waiting in Mars orbit. 

The top stage of a large rocket could take our crew from Earth to Mars orbit in about six months, and they would have something like the volume of a modern house-trailer to hang out in while they are in transit. Three or four-person crews would be plenty.

It might take fifteen years to build up the orbiting base, but it’s all waiting in Mars orbit for their arrival. This brings up the next point. Other than the International Space Station itself, all of these cargos would be launched from Earth. Everything is built in a factory, and not in orbit.

They would use tried and tested, existing technologies, except for the upper stage manned package which is specially designed for the Mars flight. Yet we’ve put packages onto the Martian surface, coming within a few kilometres of the target, and putting a package in orbit is much easier. This system requires building up flexible launch capabilities over the long haul.

An option is to bring the manned mission package to LEO via old-fashioned shuttle technology, which implies the building of a fleet of new shuttles. Then the Mars mission is essentially launched from the cargo bay of a much larger shuttle than the one we are familiar with.

The problem of using the present shuttle technology for flight to Mars is of course the problem of duration. If no other cargo is carried, the ship is still not very efficient in terms of life support, storage, and viability over a period of months or years with humans aboard. The present design is not adaptable.

This is in spite of the cargo bay in the back, however, if shuttles could rendezvous with and acquire additional tankage in LEO, then the problem is relatively well-solved without attempting to build Battlestar Galactica-type ships on orbit, with all the attendant problems of manpower, supervision, housing, supply and quality control. And again, the crew has so much space and mass allotted to food, water and life support that the interior space really isn’t that large. For the flight between Earth orbit and Mars orbit, aerodynamics are of no consequence. It doesn't matter what the package looks like.

In order to escape an orbit, simply add power. (Peo. Wiki.)
Simply put, rather than send one big ship to Mars with everything in it, all in one go, we send a bunch of little cargos to Mars on missions that are unmanned.

Rather than assemble our dream spaceship in LEO, and then shoot it off to Mars and hope for the best, shoot a bunch of little cargos off to Mars. The first crew to the new Mars station begins further, more flexible assembly. The first mission studies the planet’s surface for the best place to situate the first scientific colony as fresh cargos and fresh crews are already in transit from Earth. Each manned mission retains capability for two-way flight, at much lower cost than a large, fully-contained mission. Each mission deposits some surplus of resources on our new Mars station…

When a crew arrives in Mars orbit, some reserve of food, water and life support onboard their machine would be necessary, (10 to 20 % of overall figures) but unused supplies go into the base reserve for future demands. When planning a Mars-to-Earth return flight, the machine could be designed to rendezvous in LEO with a shuttle. It could re-enter, and make a water recovery, or glide down using lifting body technology, speed brakes and sturdy landing skids with a drag 'chute for utter simplicity of design. Allowing a ten percent reserve for maneuvering on this return flight, it seems almost inevitable that most missions would actually transfer excess fuels to the station before departure. In the event, a ship could reasonably be topped up if necessary and circumstances arose.

Orbital transfer. (AndrewBuck. Wiki.)


*You need a motor at the back to get it going, and one at the front to slow it down. The other two are back-ups.

Every component of the space station has survived high-gee lift from Earth to LEO, however, once bolted together, various angular moments come into play when thrust is introduced to the configuration. Without study, the Space Station is presently an unknown quantity in structural terms.

Components that survived high-gee compression forces might not have equal tensile qualities or torsion resistance.

In the Lunar landings, crews descended to the surface aboard a landing module while a pilot stayed behind in an orbital module. When returning to orbit and rendezvous, the actual landing gear remained behind. Only a small pod blasted off from the top of the lander, carrying two crew members after a relatively short stay on the surface. Considering the ships were built by men and women using slide-rules and paper drawings, it was a remarkable achievement.

However, when descending to the surface of Mars from the Mars Station, an unmanned lander can descend by remote or autonomous control. The following crew lands near a spare lander, which in some degree is a distinct tribute to Robert Zubrin, author of The Case for Mars and his multiple redundancies.

**the cocoons are basically just streamlining. They protect assets from Earth’s atmosphere during launch, and offer some protection from micro-meteors and the consequences of direct heating by the sun during transit on components, including those all-important fuel tanks. Cocoon shells may be useful for little more than additional shielding from cosmic rays and solar flares once on-site. This alone is not really enough reason to transport them all the way to Mars. Slightly modified, they might act as unpressurized storage bins for bulky and non-essential stores or waste/scrap materials, containers, tools, etc.

The planet Mars has about 0.38 the mass of Earth and is correspondingly quite a bit smaller in diameter.


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