Oort Cloud Colonisation.
2.0 Travel
Journeys of the order of 1000s of AU cannot be made economically using chemical rocket propulsion. This article will also disregard propulsion methods that involve the generation of gravitational fields, or other "hyper-drive" technologies which are not achievable in the near future. We will also stipulate that for a viable outer Oort Cloud economy, the means of transport to and from the colonies has to be highly reusable.
Fusion rockets seem to be a promising prospect for exploration of the outer Solar System. However, they still require fuel and a reaction mass which means for journeys over 100 AU, they would require a very large craft. Also, if they make journeys operating at very high sustained energy levels, reusability and reliability may be hard to achieve. Even if a journey to the outer Oort Cloud is broken into several steps, fusion rockets would require very great improvements over their current theoretic capabilities to be economic for such travel. They, along with other technologies such as advanced plasma drives, may be useful for shorter journeys between Oort Cloud objects, but for the longer phases of travel, there is only one real candidate that could be achieved in the near term - namely beam power.
If a vessel could undergo a sustained average acceleration and deceleration of about 1 G for the entire duration of a flight of 50,000 AU, the journey time would be about 1.7 years. Beam power in the form of laser sail or particle beam magnetic sail could achieve this, but would require high powered beam generators at both ends of the flight. Also, to maintain a force equivalent to 1 G for the entire flight without using inordinately powerful beams, it may be necessary to have additional beam generators or lenses stationed at intervals on either side of the flight trajectory. This would overcome problems of beam divergence, but would require a sophisticated control system to correctly coordinate the the beams with the motion of the vessel. In theory such a system is achievable with current technology but the challenge is formidable. The standards of accuracy required to achieve the flight are very demanding, and there cannot be any serious error. The craft has no significant propulsion of its own. Should it exceed very narrow limits on its trajectory with respect to the beams, or should the beams be compromised themselves for any significant amount of time, the craft would be lost. Multiple redundancy in critical control systems of the vessel and multiple redundancy in the number and location of beam sources will be required to make this sort of travel practical.
Given the time interval of nearly 300 days between the stations at each end of the journey, a craft leaving at one end has to assume that the destination station, without any communication about the vessels position and velocity, will correctly switch on the deceleration beam, months in advance of the vessel reaching the halfway point of its journey. For this arrangement to work, the vessel must stay on the beams as it travels and hope that they are precisely aligned with the required trajectory. No doubt, sophisticated procedures and protocols can be established to make any logistical error effectively impossible, and eventually beam generators could be established in multiple shield like configurations beyond the endpoints of the normal flight path, to catch any runaway vessels. The requirement still remains, that the craft must be able to precisely orientate itself onto the beams it receives. In the event of alignment control failure, the only possibility would be to have some kind of lifeboat or lifeboats with their own controls and sails to which the crew and passengers could evacuate.
The risks of beam propelled flight to the Oort Cloud and beyond could then be managed with the development of spaceways and spaceships with multi-level fail-safe features. Even reducing flight times is possible if the beam intensity is increased, although for manned flights it is not known what G-forces can be sustained over a long period of time. Current designs of fluid immersion suits provide protection from G-forces for pilots up to about 10 G, with a theoretical limit of about 15 G for this technology. These suits are designed for short temporary exposure to high G-forces and it is not known exactly what sort of prolonged protection they would provide, but it would be much less than 10 G. For prolonged protection, full immersion in a breathable fluid would be required, and in theory, if a breathable fluid could be found that has a density similar to water, prolonged G-forces of 20 G or even higher are possible. The onboard time for a journey of 50,000 AU at an average acceleration of 20 G would only be about 100 days. Such journeys would be considerably more challenging in many respects compared to a leisurely 1 G cruise.
Even if a journey of nearly 2 years is required to reach the outer Oort Cloud, this may not necessarily be a great hardship. The craft could be large enough to provide very comfortable accommodation, with powerful computer and media facilities on board for study and recreation. Food and water would be mainly recycled but hopefully to a standard that would be indistinguishable from fresh sources. Gravity would be very close to normal for much of the trip and solar radiation hazards would be negligible for most of the journey also. Some relatively light shielding from cosmic radiation would be enough to keep travellers in excellent physical health for the duration of the flight.
Study could be an excellent way for travellers to put their time to good use. This university definitely intends to provide courses for such students that would calculate the time allowed for assignments and exams in onboard time. Students and researchers preparing publications would still have to submit their work by an agreed deadline in standard Galactic time. That would also include the transmission time to an agreed submission point. It would be advisable to check suitable adjusted timetables and calendars frequently.
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Abstract
1.0 Introduction
2.0 Travel
