Realistic fast Interstellar Propulsion Methods

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Discussion Overview

The discussion revolves around realistic methods for fast interstellar propulsion, specifically aiming to achieve travel to a nearby star system approximately 4 light-years away within a timeframe of around 7-8 years. Participants explore various propulsion concepts, including particle accelerators, fusion, antimatter, and light sails, while grappling with the constraints imposed by thermodynamics and energy efficiency.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses frustration over the lack of viable propulsion methods that can achieve high velocities without violating thermodynamic principles, noting that even with an efficiency of 80%, the results are unsatisfactory.
  • Another participant challenges the assumption of 1000 years as a maximum travel time, suggesting that a more realistic goal would be around 7-8 years, and questions the motivations for the journey.
  • Concerns are raised about the feasibility of converting a significant portion of the ship's mass into energy to reach half the speed of light, with one participant stating that current technology cannot achieve this.
  • Participants discuss the implications of the rocket equation, emphasizing that lower efficiency necessitates carrying more fuel, complicating the propulsion challenge further.
  • There is a mention of the potential for a source of metallic hydrogen in the destination system, which serves as a plot point in the participant's hard sci-fi novel.
  • One participant expresses disbelief at the low efficiency figures for particle accelerators, questioning the practicality of the proposed methods and the harsh realities of interstellar travel.

Areas of Agreement / Disagreement

Participants generally agree on the difficulty of achieving fast interstellar travel within the constraints of current technology and thermodynamics. However, there are competing views on the feasibility of specific propulsion methods and the assumptions regarding efficiency and mass-energy conversion.

Contextual Notes

Participants acknowledge limitations in their calculations and assumptions, particularly regarding the efficiency of various propulsion systems and the practical implications of carrying sufficient fuel. The discussion remains open-ended, with no definitive solutions presented.

Who May Find This Useful

Writers and enthusiasts of hard science fiction, as well as individuals interested in theoretical physics and engineering challenges related to space travel.

  • #61
Drakkith said:
... REALLY big fuel tank...

... your five-million metric ton spacecraft ...

This measure of "big" is disappointing IMO. If your puny economy ride was parked by Neptune L5 it would need to be 50 km just to be detectable. Need to up that by 5 to 7 orders of magnitude
 
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  • #62
I've probably mentioned this before but the most "realistic" option we have now seems to be Dr. Zubrin's Nuclear Salt Water Rocket.

To quote Atomic Rockets:

"[...]. Zubrin then goes on to speculate about a more advanced version of the NSWR, suitable for insterstellar travel. Say that the 2% uranium bromide solution used uranium enriched to 90% U235 instead of only 20%. Assume that the fission yield was 90% instead of 0.1%. And assume a nozzle efficency of 0.9 instead of 0.8.

That would result in an exhaust velocity of a whopping 4,725,000 m/s (about 1.575% c, a specific impulse of 482,140 seconds). In a ship with a mass ratio of 10, it would have a delta V of 3.63% c. Now you're talkin..."

Also Wiki on the NSWR.
 
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