INTERSTELLAR flights will take years; thanks to G-force. Thought Experiment's vessel would reach 60% light speed (.6c) after 323 days of g-force acceleration (distance is about .3 LY); thus, it would need another 323 days (another .3 LY) to slow down just prior to arrival at destination star. Thus, this much g-force (646 days) enables the vessel to cruise the interim distance between acceleration and slowdown at a constant velocity of .6c. For example, a trip to a nearby stellar system, Alpha Centauri, would only take about 8 years (as observed from Earth).
INTERSTELLAR G-force consumes considerable fuel. If 0.1% of the vessel's mass can fuel one day of constant g-force acceleration; then, G-force flight for 646 days would require 46% (=100%×(1-.999646)) of ship's original gross weight (GW). Since 646 days of g-force only covers a distance of .6 LY, common sense compels us to conclude that g-force propulsion over most interstellar distances (>4 LYs) would require much more then 100% of vessel's GW (more fuel then ship, not practical). Thus, TE assumes that a vessel must g-force accelerate for about a year to gain feasible velocity (significant portion of c); and TE further assumes that vessel must cruise at this velocity for several years before deceleration and arrival.
INTERSTELLAR travelers must maintain awareness. Constant comm stream with Mother Earth. It's very likely that one of the many "chores" for interstellar crews will be to deploy and recover comm pods, deployed to assure constant communications with home station at Earth as well as the many other interstellar vessels along same route.
Not only is this desirable for many reasons, consider this overwhelming factor - if this ship encounters unexpected hazards (large debris such as ejected comets and asteroids, rogue planets, brown dwarfts, singularities, even comm modules from previous flights), the time that communications terminate will alert listeners to exercise caution during subsequent trips to that stellar destination.
Three Sections:
+++Getting There+++ |
G-force acceleration/deceleration plus a lengthy cruise make interstellar trips practical.
There are many other concepts for interstellar travel; most are infeasible and/or inpractical. For example, warp drives, worm holes and other theoretical mind exercises are not feasible. "Sailships" and generational space trips are not practical. However, a few concepts, such as the Bussard Ramjet might prove useful during the long cruise portion of an interstellar voyage.
Recall Einstein: Regardless of relative velocity, all observers measure same value for c. At start of voyage, two obervers, Earth bound Alan Ein (Al) and ship board Bertrand Stein (Bert), are at relative rest, and they both measure light speed, c, as 299,792,458 meters per sec (m/s). After Bert g-force accelerates for one day, Al observes Bert's velocity to be .283% c; thus, the remaining velocity, 99.717%c still remains to be achieved. However, Bert still measures c as precisely 299,792,458 m/s.On second day, Bert continues g-force acceleration, and he again plans to achieve .283% c; thus, remaining velocity will still be 99.717%c. Again, both Al and Bert still measure c as precisely 299,792,458 m/sec. Everyday, Bert continues to calculate .00283c achieved with a constant remainder of .99717c. Fortunately, Bert does not despair because he notices that home star, Sol, is receding at ever greater speeds; also, destination star is approaching at ever greater speeds. Thus, light speed remains constant, but g-force changes ship's relative velocity compared to departure star as well as destination star. Back on Earth, Al continues to measure a daily increase in Bert's velocity. Intuitively, one would think that a constant daily increase of .283% c would cause a g-force vessel to achieve light speed after 354 days (354 days × .283%c/day = 100.182%c). However, Einsteinian concepts clearly state that cannot happen. Thus, Thought Experiment (TE) assumes that following exponential equation is a better model of g-force velocities ("t" is time in days). Einsteinian: vt = c [1- Rt]= c[1 - .99717t] TE assumes: After 354 days of g-force, Al measures Bert's velocity, v354 , as 63.331% c.
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