The Left Seat
by Jim Slade
Current Perspectives on Human Spaceflight
2/20/2006
The success rate of the crew on STS116 and their Houston managers demonstrates once again what high value the human hand and mind have in the conduct of this enterprise. Robots probably would have been stymied by the situations the astronauts encountered in what should have been the simple matter of folding a sail.
However, the unexpected nature and the complexity of such events, not to mention showstopping weather problems, take time for resolution and time is one of the resources least available to the space agency. A mandatory retirement date for the shuttles (in 2010) leaves little room in the schedule for the unforeseen. Even a week's slip throws the plan out of kilter. This has been a glaring fault of the Bush Administration's plan for the on-going program and, in my opinion, will be addressed as the deadline draws nearer. Even more troubling is that in the program laid out by NASA to meet the administration order, the three shuttles will be retired individually as they complete certain missions instead of keeping each spacecraft on flight status until the closing date. Endeavour, the newest of the trio, will fly the concluding mission to the International Space Station.
If, for some reason, the station is not complete by the end of 2010, what then? Will a new administration put such value on the project that it will choose to extend the life of the space shuttle for however long it takes? Or, having other plans, will it wash its hands and say, "That's enough." Nothing would surprise me at this point, but since the partner nations would be the ones to suffer most from a broken White House promise, that would be a foreign policy problem of some importance.
And how will the station be serviced in the absence of the shuttles?
The first visit by the new American spacecraft, Orion, is not scheduled before 2014. If the shuttle's retirement date holds, that will leave a gap of some four years in routine access by American spacecraft. The Japanese and Europeans have been working on crew vehicles to supplement or augment the Russian Soyuz, but their availability is uncertain.
So, what about these space shuttles?
As this is written, Discovery (OV-103) is completing its 33rd flight.
Atlantis (OV-104) will make its 28th flight in March of 2007 and Endeavour (OV-105) will launch again in June of 2007.
The shuttle design stems from work done in the 70s by a team which included USAF engineers who wanted the spacecraft to be capable of launching military payloads as well as civilian. So, in many ways, the shape of the spacraft's cargo bay (60 feet by 15 feet) was cemented by the need to loft Air Force satellites. Other objects, including space station modules, have dimensions dictated by those same requirements. Since the shuttle's primary mission was to have been a service truck for a space station, all those things dovetailed nicely.
The shuttles have been remarkably durable and, once in space, very maneuverable. They fly in the lower atmosphere much the same as any large airplane.
Needless to say, their complicated design makes them difficult to launch.. Once underway, however, they have so-far unparalled lift capacity; between 36,200 pounds and 54,000 pounds, depending on their orbital track. The lighter weight is occasioned by the extra fuel required to reach the Space Station, which flies at an inclination of 51.6 degrees to the equator. The heavier capacity is allowable when the shuttles go to the easier equatorial orbit, such as that to be flown when the Hubble Space Telescope is serviced; another mission that must be flown once more before the retirement date.
In summary, the shuttle was and remains very good technology for its time in spite of what some see as its "Rube Goldberg" aspect. The fact is that in our current state, it is the very best we know how to do..and it cannot climb much beyond Low Earth Orbit, so that's why we're returning to the moon pretty much the way we got there in 1969. The basic platform for the projected moon missions is Apollo's and the improvements are based on what we've learned since. In the words of Boeing Aerospace, the planned Ares Crew Launch Vehicle will be an "in-line, two-stage rocket configuration derived from existing space shuttle solid rocket motor and booster technology." Its "primary mission will be to carry astronauts and supplies to the International Space Station and to an earth departure stage for transport to the moon." The "earth departure stage" will be atop a larger cargo carrier that will use two modified shuttle boosters plus J-series engines based on the Saturn 5 design. Ultimately, this stack will loft the lunar lander, crew module or heavy cargo out to the moon.
So, the more we know, the more we repeat ourselves.
But what are we giving up when we abandon the shuttle design? Here are a few things offhand:
Reusability. Rockwell's original advertising slogan for the shuttle project was: "When a spaceship lands on Earth, it comes from Rockwell." The shuttles, designed as flying machines, are able to land intact on a runway, be serviced, and then used again within months. It's not airline turnaround, but it is a turnaround.  Discovery has just completed its 33rd flight and will be ready to fly again after a systematic overhaul. Conversely, the spacecraft and rockets in the new Constellation program will have limited reusability. Unlike Apollo, the crew capsule, "Orion," will probably parachute home to dry land, so the 16,000 pound, four crewmember capsule may eventually be reusable as many as 10 times. The 5-segment boosters on both the crew launcher and the larger cargo carrier will be reusable in a manner similar to the shuttle boosters. Everything else in the new system is "expendable."
Robotic Arm. There are no plans at this time to duplicate this versatile system on the new spacecraft. There is discussion.
It's Our Only Non-Military Heavy-Lift Rocket. Already discussed. Any very heavy loads will have to wait for the new cargo carrier, which will have a 130 mTonne capacity.
Wings. Wings give you options for landing. Parachutes take you where they're aimed.
Wheels. Put it where you need it.
While none of these things are indispensable, they do represent solid advances in the art of spaceflight and will be missed as we revert to an earlier and simpler process.
Now. The moon and then maybe Mars.
One of the advantages of the new/old system is that it puts the crew back on the tip of the arrow. The Apollo-style Orion rides up on top where it is out of the way of falling foam or ice. It also sports an escape tower which can jerk it free of an errant rocket and is being designed to put the crew down on land, not on water, although ithat may happen, too.
It is being designed to dock to the space station in Low Earth Orbit and for 200-plus day missions at the moon.  It will carry a crew of 4 on those two missions and can be modified eventually to haul 6 out to Mars.
It will orbit untended around the moon while all four of its passengers go down to the surface for however long they are ordered to stay aboard what looks like a "beefed-up" Apollo Lunar Module. First stays on the moon will be for a week; as a permanent base is developed, later tours will last up to six months as is routine now on the International Space Station.
Planners are studying the advantages of establishing bases at the moon's south pole, initially. The 1969-1972 landings were in temperate zones near the terminator line at the moon's equator chiefly because those areas were easiest to reach and were most accommodating to our technology. 
Today, the south pole has several good points in its favor, including almost constant sunlight for solar power, the possibility of finding water frozen in the deep shadows of the craters there, quick, lighted access to the moon's far side where the very dark night periods would allow placement of a variety of telescopes free of the influences of Earth's light or radio frequency interference.
No one knows what will be found on the moon in terms of mineral wealth, or if any is found how difficult it will be to use. Finding water would be a tremendous bonus, of course, since transporting it would be very costly. Maybe the moon will have nothing to generate the "return" that so many in and out of government think is a requirement for doing any kind of science. The moon may be totally barren by human standards, but the return in knowledge could be astounding. This is a journey of the human spirit and money can never be the bottom line.
The fact is that if this nation and any partners it recruits really want to build an outpost on Mars someday..for whatever reason..we will have to learn how to do it on the nearby moon, which offers a fine vacuum, lighter gravity, extremes in temperatures, no weather or quakes, and vast, unexplored territory.
Advocates of going directly to Mars are passionate in argument and long on theory, but neither they nor we possess the practical knowledge or anything like working hardware. The moon is where all that will be developed, building on the knowledge already gleaned from our Apollo experiences and from shuttle and space station concerning the long-term effects of off-world travel on humans.
American spaceflight has always been a steady march of small, intermediate steps. Robots went to the moon first to see if we really could land there and to survey the terrain. Mercury and Gemini were progressively sophisticated steps in the Apollo buildup. Before space station, there was Skylab. Before shuttle, there was Apollo. Before Mars, there will be the moon. It's the only sane way.
There are exciting times ahead.
I can hardly wait.
Jim Slade
12/20/2006
Photos courtesy of NASA
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