Why Is Space Travel More Complex Than It Seems?

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Discussion Overview

The discussion revolves around the complexities and challenges of space travel, including the effects of relativistic speeds, the behavior of materials in space, and the implications of magnetic fields. Participants explore various theoretical and practical aspects of these issues, touching on concepts from physics and engineering.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that the challenges of space travel are often underestimated, citing issues like the danger posed by space debris and the effects of magnetic fields on spacecraft sensors.
  • Others propose that while piercing the interstellar medium at sub-light speeds may be survivable for lightweight spacecraft, significant challenges such as surface sputtering and radiation damage from interstellar medium collisions remain.
  • Concerns are raised about the implications of relativistic mass, with some participants suggesting that it could lead to catastrophic failures in fission or fusion reactors at high speeds, while others challenge this view, asserting that criticality depends on mass in the reactor's rest frame.
  • There is a discussion about the concept of an absolute frame of reference and the implications of relativity, with some participants questioning the validity of certain assumptions in relativistic physics.
  • Participants also discuss the observed velocities of meteors, questioning why they do not reach higher speeds despite the theoretical limits of physics.

Areas of Agreement / Disagreement

The discussion features multiple competing views, particularly regarding the implications of relativistic mass and the nature of reference frames in physics. There is no consensus on these points, and participants express differing interpretations of fundamental concepts.

Contextual Notes

Participants express uncertainty about the definitions and implications of relativistic mass and reference frames, indicating that their arguments depend on these concepts. Some statements reflect a lack of agreement on the foundational principles of relativity.

Who May Find This Useful

This discussion may be of interest to those exploring the theoretical and practical challenges of space travel, as well as individuals studying the implications of relativity in physics.

Z0dCHiY8
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Most sources of pop culture & even engineering ones have failed to provide the key problems of space traveling. For example, dv ain't that hard as aerodynamics of Space. For 1st glance, it looks ridiculous == Space is Vacuum. Mostly, yes.. but Space has a lot of dust & gaseous clouds. Just one gram of material at 100 km/s equals to 5,000,000 Joules, it's roughly worthy to 1 kg of TNT & actually, far more lethal (detonation speed for tnt is only several km). Second trouble gets to be magnetic fields == at the least, eddy currents shall make a lot of noise onto spaceship sensors; more worse issue will be full blackout for unknown time; at worst scenario, sensors get fried entirely.
 
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You should look at Breakthrough Starshot related research.
In brief, piercing interstellar medium at sub-light speed may be theoretically survivable for light-built spacecraft , although surface sputtering and radiation damage due ISM collisions are significant. Magnetic fields, on other hand, are insignificant - EMF is created by field gradients, not by field itself.
 
trurle said:
EMF is created by field gradients, not by field itself.
that's related to velocity of spaceship == greater speed, greater fluctuations of magnetic field.
trurle said:
piercing interstellar medium at sub-light speed may be theoretically survivable for light-built spacecraft
actually, the're a lot of problems to sail within Solar System even at 100 km/s.. sub-light speeds are purely suicidal. For instance, growing of relativistic mass can easily lead to explosion of fission or fusion reactor (under critical mass at normal speed become critical at sub-light). Electrical circuitry will run inadequately too. however, it's very unlikely to reach 1000 km/s w/o explosion by whatever reason.
 
Z0dCHiY8 said:
For instance, growing of relativistic mass can easily lead to explosion of fission or fusion reactor (under critical mass at normal speed become critical at sub-light). Electrical circuitry will run inadequately too. however, it's very unlikely to reach 1000 km/s w/o explosion by whatever reason.
Effects like you describe are direct violation of principle of relativity.
 
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what exact principle & how does it get violated?
 
exact example, please.
 
Z0dCHiY8 said:
... growing of relativistic mass can easily lead to explosion of fission or fusion reactor
Since "relativistic mass" doesn't mean what you seem to think it means, that statement is nonsense.
 
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Z0dCHiY8 said:
exact example, please.

All inertial references frames are equivalent. Or, to put it another way, a spaceship traveling at 100km/s relative to Earth is fundamentally equivalent to a spaceship at rest relative to the Earth. Neither ship is absolutely at rest, nor can you attribute any absolute velocity to either ship. It is not the case that the Earth represents some sort of special, absolutely at rest frame of reference.

In particular, relativistic mass represents the measure of the (kinetic) energy of one object in a reference frame in which it is moving. It does not represent any physical change in the object, as explained above.

For example, in the reference frame of the spaceship, the Earth is moving at 100km/s, but clearly the Earth undergoes no inherent physical change just because it is observed by something in relative motion to it.
 
  • #10
The relativistic "mass" is only a crude explanation of how an outside, stationary, observer can understand what he is seeing in his time and space measurements. Considering it a real change of mass is widely discouraged and causes great confusion. The inertially moving person experiences all of his physics as though he is not moving at all. There will be no explosion of a reactor just because it is moving.
 
  • #11
Z0dCHiY8 said:
growing of relativistic mass can easily lead to explosion of fission or fusion reactor (under critical mass at normal speed become critical at sub-light).

This is wrong. Criticality of a reactor does not depend on relativistic mass. It depends on mass in the reactor's rest frame, which does not change.
 
  • #12
all our theoretical assumptions onto relativistic speeds could go further & further. Frame of reference is very contradictive term for all of that theory. For instance, how could we say about light speed, if we don't determine the Absolute Frame of Reference? Second moment, if speed of light is maximum for this Universe, how could we assume the same physics for all possible speeds of this Universe? It has no sense, if speed affects not just kinetic energy of body, but its time/geometry/mass. But my point stays for more humble ranges of velocity, for instance, we have curious statistics..
The majority of visible meteors are caused by particles ranging in size from about that of a small pebble down to a grain of sand, and generally weigh less than 1-2 grams.
------------------
The Leonid meteors represent the fastest known shower meteors, barreling in at 72 km/sec
https://www.amsmeteors.org/meteor-showers/meteor-faq/
even lightweight pieces of rock doesn't show astonishing speeds.
 
  • #13
Z0dCHiY8 said:
Frame of reference is very contradictive term for all of that theory.
No, it is not. Your understanding may be contradictory (not "contradictive") but that's your problem not a problem with physics.

For instance, how could we say about light speed, if we don't determine the Absolute Frame of Reference?
That's not a problem because there is no such thing as an absolute frame of reference

even lightweight pieces of rock doesn't show astonishing speeds.
That is incorrect. Relative to a particle in the CERN accelerator a small pebble laying on the ground next to your foot has an ASTONISHINGLY high speed (very close to the speed of light). For that matter, so do you.
 
  • #14
phinds said:
That's not a problem because there is no such thing as an absolute frame of reference
And what is a point of maximum possible speed?
 
  • #15
Z0dCHiY8 said:
And what is a point of maximum possible speed?
The speed of light is a special case. It is the maximum possible actual speed and it is the same in all reference frames. You really need to study the basics some more.
 
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  • #16
phinds said:
The speed of light is a special case. It is the fastest possible actual speed and it is the same in all reference frames
well, then we cannot claim the same physics for all FoFs.
 
  • #17
actually, i'd like to know why meteors get such humble limit of their velocity. :)
 
  • #18
This thread is degenerating into personal speculation by the OP and is now closed.
 
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