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Napkin Sketch #2 Join Our Hero as we return for more thoughts on Conestoga - this time, with a look at the possible design of the Conestoga - the basic spacecraft used by the colonists following the designs in the finished Conestoga documentation.

The first question that must be asked, in considering the design of a Conestoga spacecraft, is "What is the target mass?" Here on Earth, we tend to think in terms of size; how many bedrooms does a house have, how large are the carry-on bins on an aircraft, how many parking spaces will that new SUV cover. When we're talking about spacecraft, however, the critical question is mass. That pound of weight must be picked up from ground level, carried straight up at least 100 miles, and accelerated from a dead stop to at least 4.7 miles/sec, or nearly 25,000 meters per second. That takes a tremendous amount of energy, and currently, at least, the only way to do that is to burn massive amounts of very cranky liquids like oxygen and hydrogen.

There are currently about nine launch vehicles currently available to civil projects, and capable of lifting a "useful" mass into LEO, Low Earth Orbit. I say "about nine" because there are a couple of launchers "in development" that may also be available, and a couple of those I list as "available" may in fact not be.

Four of those are Russian (although one is also now American), two are European, and three are American. There may also be a Japanese launcher available, the HII, but all of the data I have available on the HII is out of date and suspect, so I will not list it here. The launch capability of these launchers ranges from 7.3 tons (6600kg) for the Ariane 44L from the ESA, to 100 tons (90,900kg) from the Russian Energia booster. Most launchers are capable of launching less than 20 tons (18,000kg), although NASA's space shuttle can lift 29.5 tons, 26,800 tons. Of course, you can't use the shuttle without permission from the US government, and we've already seen NASA's stance towards anyone other than a NASA-approved astronaut travelling to orbit. Dennis Tito, anyone?

My own feeling is that Russia is any private organization's best chance at buying a ride to orbit. This leaves four potential vehicles; the aforementioned Energia, which is not in common use, the Proton, at 19.5 tons (17,700kg), the Zenit, at approximately 16 tons (14,500kg), and the SL-4/6, at 7.5 tons or 6800kg.

In that mass, you must take everything you will need to survive, plus yourself, plus the vehicle and fuel to travel from LEO to the Moon and land safely.

The design that I have in my mind is four cylinders stacked around a common center. Each cylinder is made to be as flimsy as possible; made from aluminum and tunsten, with a minimum of steel, those four cylinders are going to be home. A fairing, used for launch and discarded as soon as the booster has cleared Earth's atmosphere, wraps around the four cylinders. The spaces between the cylinders is filled with a lightweight framework to hold the vehicle together, fuel for the engines, and such cargo as can be carried without damage by vacuum and can't be carried inside the cylinders. One cylinder will be your farm when you reach the Moon; this means it probably can't carry much cargo inside it other than its own livestock and crops and support equipment; if your farm is transported "dead", i.e. you won't be growing anything until after landing, then it can be used for cargo - but you'll need more cargo, since you won't be able to grow any food on arrival. The other cylinders - living quarters, workshops and lab space, and storage - is filled to the brim with cargo of all kinds. Food, tools, mining equipment, spare parts, reading materials.

The forward end of the spacecraft is a ship in its own right; a self-contained engine, fuel supply, and flight deck. It doubles as a passenger compartment for the overall ship and flight deck for the trip; after arrival on the Moon, it might be used for point-to-point trips on the lunar surface (for prospecting, rescue missions, exploration, or trade) and as such the engine is a relatively simple, low-thrust, alcohol-and-oxygen design. It does look odd, though; narrower at the bottom than the top. This is because the top is a smooth expanse of removable heat shield; in an emergency that threatens the survival of the colony, the human occupants can abandon everything and return to Earth, splashing down in the sea like early American space vehicles. Why on top? Because it's easier than trying to accomodate an engine system AND a heat shield on anything that isn't purpose-built for atmospheric re-entry.

When the Conestoga arrives in lunar orbit, we have two choices; we can try to land the vehicle in one piece, or we can break it apart and land each part separately. Both options have their advantages, and I suspect both methods will be used. By landing as one ship, the biggest advantage is simply that there need only be one successful landing; everything is together, in the same spot, and last-minute changes and corrections to accomodate terrain or mechanical problems need not necessarily spell disaster. In addition, your engine system is made simpler; you probably need only one engine, one navigational system, and so on. On the other hand, you need a much more powerful engine, which is one of the advantages of multiple landings; smaller engines to do the job. You can also land all the cargo first, via remote control (or even automated landing systems, possibly) and only attempt landing yourself if the cargo you need to survive landed safely. On the other hand, you need multiple engines, need to make multiple landings, and run the risk of having one or more of your vehicles land in the wrong place.

So those are it; the most basic questions that need to be answered about how you're going to travel to the Moon. Next, let's consider how you're going to travel there; you can't exactly ask AAA to make a TripTik for you...