Cosmic Tales - Adventures in Sol System

by T. K. F. Weisskopf

  The new emphasis on SLI became: "Get a way to carry payloads and people to the ISS as soon as possible because the Shuttles are failing." This new SLI emphasis was decided about nine or so months before the Columbia accident. It makes one wonder doesn't it?

  At any rate, the new emphasis for SLI was for it to become a split-personality program. The two personalities of the program are the Orbital Space Plane (OSP) and the Next Generation Launch Technologies (NGLT). The OSP is to be a small person-carrying lifeboat that will be strapped on top of an expendable rocket. The only thing reusable on the OSP concept vehicles will be the lifeboat itself and, of course the lifeboat will never go higher than an ISS orbit!

  The NGLT personality of the program was put in place in order to keep the advanced or next—generation flavor in SLI that might one day enable single stage ETO vehicles or at least reusable vehicles. This seems for now to be purely political in that the OSP personality has the largest share of funding.

  Hopefully, the split-personality program will not become viciously self-competitive and eat itself politically and economically from the inside out. It is possible that the program will generate useful space vehicles in the future, but the odds of success seem low. The main issue with SLI now is that it will be the program that drives the American manned space effort for the next generation. It is obvious from the program's requirements that no consideration for higher than LEO are being made. If SLI continues as planned, we will be stranded below the ISS-type orbits for another generation. So getting from Earth-to-GEO may be tough to do in the next twenty or so years. For this section of space travel we must hope that the Chinese will initiate a bold space program that will spark a new space race. They have plans to set a Chinese team on the Moon by 2010 and once they put their first "taikonaut" into space, perhaps we will take them seriously and change our split-personality ETO space program to something more useful. (Note: One must wonder if this is what has sparked President Bush's new space initiative?)

  On the other hand, it is possible that ETO-to-LEO rockets will be enough. In the story, Tamara takes a rocket from Earth-to-LEO where she catches the Space Elevator and rides it from LEO to GEO. A space elevator works just like an elevator on Earth does. A space platform would be placed at LEO and one would be placed above it at GEO. The two platforms are "tied" together by a very very very strong but very very very lightweight cable. The distance from LEO to GEO is about 35,000 kilometers so you can see why the cable must be lightweight. A cable that long with a mass of just one gram per meter of length would have a total mass of 35,000 kilograms! Wow, that is just a little more mass than a Shuttle can lift. Also, a cable that is only one gram per meter must have amazing tensile strength in order to withstand the stresses of lifting an elevator car full of people and stuff. A cable with only one gram per meter in length is not much larger than fishing line in diameter. The tensile strengths required of such small cables are nearly a property of "unobtanium." However, there is recent research in carbon-nanotube-reinforced fibers and cables that are very close to having the properties required for a space elevator. NASA, industry, and even fishing line companies are currently testing the materials.

  So the elevator platforms are tied together by this extremely strong and lightweight nanotube-reinforced fiber. The elevator car simply uses motors to winch itself up or down the cable. As the elevator car moves upward it imparts some of its momentum to the elevator platforms pushing their orbits slightly lower. The orbit of the platforms will raise when the car comes back down. The platforms would also be much more massive than the elevator car and cargo so the momentum transfer to the elevator platforms would be analogous to the momentum one would transfer to a barge by diving off it into the water.

  There are presently many individuals and several companies that believe the space elevator concept is viable and doable today. Some even believe it can be constructed not just from space-to-space locations but from Earth to space like in the Arthur C. Clarke novel The Fountains of Paradise. The materials strength-to-mass ratio required to build the ground station is beyond present capabilities and the effects of the atmospheric drag on the cable increase the strength requirements for it as well. Most likely, space-to-space elevators will come first.

  Now ETO might not be that exciting for the next generation, but the NASA In-Space Propulsion Program is making leaps and bounds toward making travel within our solar system a reality. Funded by the Office of Space Science and centered in Huntsville, Alabama, at the NASA Marshal Space Flight Center, the In-Space Propulsion Program is currently developing solar sails, ion drives, space tethers, advanced chemical propulsion, aeroassist, beamed energy, pulsed-plasma propulsion, matter-antimatter powered propulsion, and many others including the space elevator concept that Tamara used to get from LEO to GEO. The In-Space Propulsion Program is currently funded and projected to be funded to the tune of a few tens of millions of dollars per year for the next five or so years.

  These concepts are being pushed to levels of development so that craft could be test flown within the next five to ten years. In fact, the solar sailing technology that uses sunlight pressure on very large lightweight reflectors like Tamara's ship the Boy's Life is currently at the state of near flight readiness. There are several NASA contractors developing solar sail spacecraft and preparing the concept for a test flight expected to be within the next year or two. Also, two separate private entities, Team Encounter and Cosmos I, are developing solar sail spacecraft for flight. The private teams might beat NASA in the race to fly a solar sail.

  Why develop solar sails? Well, actually, sails are currently the only way to carry a spacecraft into the outer edges of our solar system in a short amount of time. A sailing ship would be launched on an expendable chemical rocket toward the Sun. When the ship approaches about half the distance between the Earth and the Sun its sail would then deploy. The photons from the Sun impact the sail and deliver momentum to the sail. It turns out that a sailing ship of a few hundred kilograms or so and a sail size of about two hundred meters in diameter could reach the outer solar system in less than ten years. This size spacecraft at such a low mass is about ten years away in technology development. All of the components for such a craft have been developed in small quantities; it is now just a matter of figuring out how to put it together on such large scales. The best approach is to start out smaller.

  The first NASA solar sail flight will most likely be a square sail about fifty meters or so on a side. The mission will be to demonstrate that the technology works. It is possible that the spacecraft will be given an actual job once it has been tested. A sail of this size could sail from high Earth orbit inward toward the Sun to about ninety-five percent the distance from the Sun to the Earth. The sailcraft could sit there and watch the Sun for solar flares and other forms of coronal mass emissions that wreak havoc on our satellites and communications grids. The particles ejected from the Sun travel a little slower than light speed. So if the sailcraft that is a little closer to the Sun than the Earth detects the particles, it can send a radio signal to Earth to tell us to turn off our stuff. The radio signal should beat the Sun emission by several hours, giving us plenty of time to prepare for the bad "solar weather." This mission could be implemented in just a few years.

  The advantage of solar sails is that they use no propellant or reaction mass that is ejected from the spacecraft. The propulsion is purely provided by the incident light from the Sun. On the other hand, the propulsive effect is negligible once the spacecraft is at distances from the Sun much farther than Mars's orbit since sunlight pressure drops off as the inverse square of the distance from the Sun. So if you want to go somewhere and stop with a solar sail it must be within Mars's orbit if you plan to stop by using sunlight. However, a recent study by myself and Dr. Greg Matloff has shown that the sails can actually be used as a parachute. So a sail could fly close to the Sun to get sped up really fast and then fly out to Neptune perhaps and aerobrake or parachute into Neptune's atmosphere and
slow down to a Neptune orbital velocity. This is a brand new concept that NASA is looking into but it appears that it can be done successfully at Mars, Jupiter, Saturn, Neptune, Titan, or basically any solar system body with an appreciable atmosphere. So, the technology for sailing from Earth to Mars or other solar system bodies is at hand and soon to be flown.

  Another neat application with sailing ships is beam riders. At the end of the story Tamara has started running a large mirror that directs sunlight and focuses it onto a sailing ship. I did a study in 2000 that showed that if a mirror 100 km in diameter could be placed in a high GEO and could continuously focus sunlight onto a 100-km-diameter sail of appropriate design for about ten years, then that sail could reach Alpha Centauri in less than fifty years. Of course stopping would be another matter altogether but there are theories on how to do that by the late Dr. Robert Forward, Dr. Greg Matloff, and others. The biggest hurdle in developing these interstellar sailing ships as in "Cleaning Lady" is learning how to build such very large spacecraft. Most of the materials are available but we are not quite sure how to put them all together, yet.

  In the story Tamara encountered several "nuke tugs" that used nuclear power as the main power source for the spacecraft. NASA is also looking at nuclear fission-powered electric propulsion. This research effort is called Project Prometheus. A fission power plant the size of a beer keg or a garbage can could deliver several hundred kilowatts of thermal energy to a power converter that would then convert the heat to electrical power just like terrestrial nuclear power plants. The conversion process is about twenty-five to thirty percent efficient. Therefore a three—hundred-kilowatt thermal fission reactor could deliver about one hundred kilowatts of electrical power to the spacecraft systems. The propulsion for the spacecraft would be an advanced ion engine similar to the one that recently flew on the Deep Space 1 mission. Ion engines use a small electrically powered ion accelerator to accelerate small particles to very high velocities. These small particles are then electrically pushed out of the exit of the accelerator to generate thrust. The thrust generated is not very high but the fuel usage is very efficient. Analyses have shown that a nuclear fission electric propulsion spacecraft of this type could carry thousands of kilograms of payload to the Pluto-Charon system and maybe even the Kuiper Belt with trip times of less than twenty years. And when these types of spacecraft get where they are going they still have all the electrical power that they need from the fission reactor. One of the problems with previous outer-planet missions has been that there was no electrical power after the batteries died. A well-designed fission reactor should generate power for decades.

  Another possible nuclear rocket design would be to skip the electrical conversion part and superheat a fluid such as liquid hydrogen by flowing it through or around the reactor core. The superheated liquid is then flowed through a rocket nozzle, which would then deliver tremendous thrust to the spacecraft. The thrust generated by a so-called "nuclear thermal rocket" is much greater than that of the electric mode of operation but the fuel efficiency is very low. It is possible that the two different modes of operation can be utilized for different aspects of space missions. Nuclear thermal mode is used when high thrust or quick acceleration is needed and nuclear electric is used when long slow efficient thrusting or accelerating is needed. And of course when all the fuel is used up the spacecraft can sit wherever it is or coast along with plenty of electrical power for making scientific measurements or powering crew quarters.

  Finally there are the far-reaching and many—generations-down-the-road technologies. Although exotic means of space travel were not mentioned in the story, no essay on the future of space propulsion would be complete without at least talking about faster-than-light travel. The NASA Breakthrough Propulsion Physics program (BPP) mostly investigates these efforts. The BPP has tried to create interest and serious investigation into concepts like warp drives, wormholes, vacuum energy, and various other seemingly science-fiction-type technologies. Recent efforts have shown that our modern theories of the universe allow for such things as wormholes and warp drives, but the problem is that we simply have no idea how to build them. In fact, we have no idea where to start!

  The BPP has asked the propulsion and theoretical physics communities to combine their collective thoughts on the topic and make suggestions for a starting place. There have been several suggested experiments and many theories but few have proven fruitful to date. The most promising concepts involve the Alcubierre warp theory and the so-called Casimir effect. The details of this are too complex to go into here but suffice it to say that there still remain possibilities within known physics for faster-than-light s-cience-fiction-type travel. But this would be generations away, perhaps.

  It should also be noted that the output of the BPP has been amazing for the little funding it has received. The program has delivered many peer-reviewed concepts and papers and a few proposed experiments in just a few short years. The BPP has been alive for about five years and has had a total budget of about one and a half million dollars; that's total budget, not per years. Until serious funding is applied to the program the program will not be considered seriously. But don't fret over it too much since the scientists and engineers that grew up watching Star Trek and reading Heinlein will never give up on the idea until we have done it. The theories suggest that faster-than-light travel can be accomplished and someday we will do it.

  So, we see that there are serious direction issues within our space program. We spend immense amounts of money on our ETO capabilities but redirect the emphasis so often that we will likely get nothing to show for it. Our In-Space technologies are funded at a fairly reasonable pace (although I'm sure more funding wouldn't hurt the program) and reasonable results are being achieved. In fact, if we have a means to get the technologies off the Earth, the In-Space technologies will be able to take us anywhere we want to go within our solar system. If we want to go farther than our solar system, well we will just have to be patient. The In-Space technologies could get us there . . . with many decades if not centuries of travel time, but who wants to wait that long? The BPP efforts might develop a faster-than-light propulsion system that would take us beyond the solar system in short periods of time, and as interest increases, funding for the program will increase.

  It appears for now that we will just have settle for our own solar system and traveling within it. That's okay, as we should learn to crawl before we learn to run. The ETO technologies will be developed out of necessity. We have to go to the space station or it will eventually fall, and we have to put up communications satellites, and sooner or later the Chinese will go to the Moon, so we will develop ways to get off the Earth within a generation or two. The In-Space propulsion technologies being developed and tested today will enable us to travel anywhere within our solar system within this generation possibly and most definitely within a generation or two. That should be exciting enough to offer us great adventures like the ones presented within this anthology. So we can all look forward to some really exciting space adventures if not within our lifetimes at least within our children's lifetimes. And when we have really traveled all around the solar system and have learned to use the resources within it, then perhaps we will venture outward to the stars using the BPP-type more advanced breakthrough technologies. One might ask the question, "Are we there yet?" and the answer is simply, "It's not far now!"

  COMMUNICATIONS PROBLEM

  Of course, once we get up out of the gravity well and establish colonies, not all will be hunky-dory. . . .

  Margaret Ball

  ComCentral was fizzing with activity when Elaine arrived at the start of her shift. Little sparks of frustrated energy crackled in the air. Her colleagues were talking too fast and clipping the ends of their sentences off in a way that suggested they were barely managing to remain within the Federation guidelines for nondiscriminatory civil speech.

  "What's the matter with everyone?" she asked Jana out of the side of her mouth while
they changed places in their shared pod. "Com crisis?"

  Jana sighed. "No, just the usual. The Prajad Dal says the Islamic Renaissance has got a more powerful transmitter and is drowning out its Ram chants. The Islamic Renaissance says that having to hear Ram chants over the common band is a violation of its religious integrity. The Pieds Nus want equal time with the Naturists despite the fact their colony is about one percent the size of the Naturist -community. The VolksAlliance wants a zoning ordinance preventing nonwhite colonization of any asteroid within their sphere of influence—"

  "Well, that's not a communications issue, is it? They'll have to take it up with Colony Approval and Registration, and they'll be turned down because their 'sphere of influence' starts inside their own airlocks. I don't see where we come into it." Elaine set the general com channels plug in her right ear but left the other ear free to hear Jana's reply.

  "They can't be turned down until they apply to CAR, and they're not going to make a formal application because they know it won't work," Jana sighed. "They're using their entire common-band allocation to make speeches about it. Which means the Islamic Renaissance, the Candomble Negre, Nuevo Aliyah and oh, just about every ethnic-based asteroid community in the belt is demanding extra common-band time to make speeches against it. Except the Mixo-Lydians," she added after a pause. "All they want is to bomb the Slavo-Lydians out of the asteroid belt. And vice versa, of course."

  Once engineering and mining firms had demonstrated that it was technically feasible and potentially profitable to hollow out asteroids and set up closed ecologies for their work forces, the settlement of the lesser asteroids had been touted as the opportunity for each and every persecuted minority group on Earth to have its very own mini-world; "the ultimate gated communities" as one optimistic NASA writer had described them. What the optimists had overlooked was that many groups didn't desire to be let alone so much as they desired to persecute all the others who committed the crime of being Not Like Them. With physical access to each asteroid community well controlled at the entry locks, the rival groups took their bickering to any area where they could still overlap, interfere with each other, and try to snatch resources.