Monday, January 29, 2007



Habitat's immediate future will be as Orbiters and Cyclers, non-propulsive vehicles which leverage orbital mechanics as described in previous chapters. However, subsequent volumes describe habitats as Migrators to nearby planets and far away stars.  G-force propulsion can make interplanetary migrations very quick, and it makes interstellar cruise feasible for migrating habitats.  
Near Mars Scenario.  G-force vessel carries habitat to Mars during closest separation between Earth and Mars, 0.5 AU.
First of 4 Phases. G-force vessel accelerates for an entire day to reach .25 AU,  mid-distance of this voyage.
2nd Phase. Upon reaching midway, g-force vessel must reverse propulsion direction to decelerate.
G-force vessel continues to carry habitat to Mars as it slows down to orbital speed around the Red Planet.
When vessel reaches Mars, habitat separates and permanently enters a Martian orbit. It deploys a mirror to leverage sunlight to power habitat's infrastructure.
As more habitats travel to Mars, they can deploy at different “parking” orbits.
  1. Could co-locate with either Phobos or Deimos; they might possibly mine these Martian moon for “in situ” resources.
  2. Could park in Martian geosynchronous orbit (GSO) about 20,000 kms directly above a position on equator of Mars.

In GSO, habitat can continuously monitor designated surface location as deployed Artificial Intelligence (AI) resources prepare it for for visits by the habitat humans.
Most human visitors will spend most time in their orbiting habitat to simulate Earth gravity via centrifugal force (spin about longitudinal axis).
Some humans will spend some time on the Martian surface and subsurface, but long term reduced gravity will have serious health consequences.
Most time should be in the habitat to maintain the required muscle tone and other health features maintained by constant Earth gravity.
RETURN LEG: Phases III and IV.

3rd Phase.  G-force vessel immediately starts its return voyage without the habitat which stays at Mars.
Like Phase I, it must accelerate back to midway.
Assuming immediate return, distance/times for return leg should be almost equal to the distance/times of departure leg.
4th Phase. Returning vessel will contain some of the people as well as scientific treasures mined from Mars and its moons.
During this final deceleration, g-force vessel slows down to Terran orbital velocity.
Someday,  habitats may deploy to other positions in Earth’s Solar orbit; perhaps 60o ahead of Earth; here named Alpha.

To support this more distant destination, expand g-force vessel’s acceleration distance (dAcc) to .5 AU.
Use Newton’s motion equation to determine associated acceleration time (tAcc), 1.4 days.
As in previous example (Near Mars), the deceleration distance/time will equal acceleration d/t.

Thus, total travel time from Earth to Alpha will be:
t = 2×tAcc = 2.8 days
Further expanding service for habitats, g-force vessel could travel directly from habitat Alpha to habit Omega as shown in figure.
THIS EXAMPLE can show total time/distance for g-force vessel.
Acceleration distance (dAcc) to midway would be .866 AU and acceleration time (tAcc) would be 1.86 days.
Consider it axiomatic that deceleration time/distance equals acceleration time/distance.
Thus, total travel distance is twice acceleration distance:
d = 2 × dAcc = 2 × dDec
Total travel time is twice acceleration time:
t=2×tAcc=2×(2×dAcc/g) =2×(d/g)
Consider more typical Line Of Sight (LOS) distances to near Earth destinations.

Thus, it might be possible to quickly g-force travel to and from habitats co-located with celestial objects throughout the Solar System. Some trips would move habitats to new locations, but most trips would transport humans and cargo among many habitats.

Interplanetary Volume discusses g-force travel among the planets.
NOTIONAL EXAMPLE: For convenience, above figure shows fictional destination 2.05 LYs from Sol.
Phases of Interstellar F light. Conjectural calculations indicate that a vessel propelled throughout entire interstellar voyage would likely consume more fuel than available in all of ship's total mass. Thus, Thought Experiment (TE) assumes following baseline flight profile.
Acceleration Phase. Ship starts trip by g-force accelerating for 365.26 days and .38 LY, this will bring it to a velocity of .6443c (64.43% of light speed). Per Einstein's "Equivalence", occupants will feel same gravity like force as if static on Earth's surface.
Deceleration Phase.  At exactly .38 LY prior to destination, ship will g-force slow down from 64.43% c for exactly 1 year.
Cruise Phase. Due to fuel considerations, ship will stop propulsion after 1 year of g-force acceleration. Thereafter, ship will maintain constant velocity of 64.43c for entire cruise phase (majority of voyage). Ship might use Helium-3 nuclear fusion reactors for internal power and will most likely not deploy external mirrors.
Centrifugal Force. To maintain Earth like gravity, ship will reconfigure to simulate Earth gravity via centrifugal force. During non-propelled cruise phase, cylindrical vessel becomes a habitat and rotates around its longitudinal axis throughout the entire cruise portion of the interstellar voyage. Carefully controlled spin simulates Earth gravity by pressing passengers against the inside of the outer hull.
FOLLOWING EXAMPLES use observed distances to nearby stars.

Compared to baseline profile, for nearest known stellar neighbor, Alpha Centauri (AC), shorten g-force acceleration to .9 year. Thus, vessel attains a slower velocity of .6 c and a shorter distance of .3 LY.
Assume cruise velocity of .6c for 6.13 years.
Prior to going interstellar, humans will have been living in orbital asteroid shells (i.e., habitats) for many generations. During interstellar cruise phase, humans will need to continue living in spinning habitat to maintain Earthlike conditions.
One year of g-force acceleration/deceleration is an arbitrarily chosen baseline duration. Flight planners can choose any duration by properly observing tradeoffs between fuel availability and total trip time. Longer propulsion durations means faster cruise velocity and shorter trip time; however, it also means more fuel expended.  If ship runs out of fuel, then vessel cannot decelerate; crew and passengers are stuck at that velocity FOREVER!
ACCELERATION. For more distant stellar neighbor, Groombridge 34, increase g-force duration to 1.1 year. Thus, vessel accelerates to a velocity of .699 c (greater than baseline, .644 c) and travels a longer distance of .42 LY. To observe Einsteinian physics, TE conjectures following equations:
Vt = (1 - (1-Δ)t) ×c
Vt = (1 - (1-.002823)401.775) ×c
Vt = .6963c = 120.77 AU/day
DECELERATION. At .42 LY from destination, spaceship must g-force decelerate for 1.1 year to decrease speed from .699c to an orbital velocity.
dt  = c × t + Vt / ln(1-Δ)
dt  = 173.145 × 401.77 days + 120.77 AU/day/ (-.002827)
dt  =  26,845 AU = .4245 LY
CRUISE. Interstellar flights will need a lengthy duration at constant velocity to conserve fuel. For not so near neighbors, a faster cruise speed reduces cruise duration by a few years.
INTERSTELLAR VOLUME discusses migration to nearby stars.


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