Author Topic: 99% of Light speed  (Read 30513 times)

Offline cjackson

  • Member
  • Posts: 31
  • Liked: 1
  • Likes Given: 0
99% of Light speed
« on: 08/03/2011 02:48 am »
Is it possible to build a vehicle that can accelerate to .99 C?

How would we go about doing something like this?

If at all possible, how many centuries or millennia is it before this can be accomplished?

Could a Bussard scramjet do it?

How large would a laser/maser/gaser have to be to get the craft up to such speed?

How long would it take from the crew's perspective to cross the galaxy?

How big would the craft be? I imagine a lot of fuel would be required even if you could gather propellant along the way - Bussard scramjet. What kind of fuel would be needed?

Would such a vessel help establish a galactic civilization? Or would time dilation make implausible?

What would it look like?

Are any sort of warp drives completely impossible? If so, which of the following would best for interstellar travel: beamed propulsion, matter/antimatter reaction, Bussard scramjet, or something else?

This very fascinating for me.

Offline alexw

  • Full Member
  • ****
  • Posts: 1230
  • Liked: 4
  • Likes Given: 2
Re: 99% of Light speed
« Reply #1 on: 08/03/2011 04:51 am »
Is it possible to build a vehicle that can accelerate to .99 C?
How would we go about doing something like this?
If at all possible, how many centuries or millennia is it before this can be accomplished?
Could a Bussard scramjet do it?
How large would a laser/maser/gaser have to be to get the craft up to such speed?
How long would it take from the crew's perspective to cross the galaxy?
How big would the craft be? I imagine a lot of fuel would be required even if you could gather propellant along the way - Bussard scramjet. What kind of fuel would be needed?
Would such a vessel help establish a galactic civilization? Or would time dilation make implausible?
What would it look like?
Are any sort of warp drives completely impossible? If so, which of the following would best for interstellar travel: beamed propulsion, matter/antimatter reaction, Bussard scramjet, or something else?
This very fascinating for me.

     It's possible in the sense that the laws of physics do not forbid it. Who knows how long until it's economically possible -- if the Singularity is correct, perhaps shortly thereafter :)
    Two approaches generally deemed workable are the antimatter rocket, and beamed-laser sail. (IIRC, the Bussard scramjet is thought to have some strikes against it, but I've forgotten the details.)
     At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard. 
      The size and mass of the vessel would depend on the size of the cargo. The amount of "fuel" would be unbelievable; guessing without checking the numbers, you'd want something like planetary-size solar collectors to gather the energy to power either your antimatter-producing factory or the interstellar laser.
   
      It's hard to see that a galactic civilization would be enabled by near-lightspeed sublight travel. Much easier to slowboat it and then send information around (teleporting consciousness should be easy by that time.) The possibility/impossibility of warp drives is a subject of interest to various GR theorists. There are occasional glimmers of hope ;)

     A couple of starting points you might look up are Alcubierre drive and the novel _Rocheworld_.
    -Alex
« Last Edit: 08/03/2011 04:56 am by alexw »

Offline 93143

  • Senior Member
  • *****
  • Posts: 3054
  • Liked: 312
  • Likes Given: 1
Re: 99% of Light speed
« Reply #2 on: 08/03/2011 07:54 am »
...teleporting consciousness should be easy by that time.

Assuming rather a lot, aren't you?  Considering that consciousness isn't even an objective phenomenon in the first place?

The Bussard ramjet was said to have drag issues, but I think Bussard himself said something to the effect of 'there are plenty of ways to design an interstellar ramjet so that it doesn't work'.  I'm not sure he was sold on it not being viable.

There's also the fuel issue.  They apparently found a way to catalyze proton-proton fusion so it didn't take forever, but no one's quite entirely sure what it was...
« Last Edit: 08/03/2011 08:22 am by 93143 »

Offline Nomadd

  • Senior Member
  • *****
  • Posts: 8840
  • Lower 48
  • Liked: 60430
  • Likes Given: 1305
Re: 99% of Light speed
« Reply #3 on: 08/03/2011 11:44 am »
 I'm pretty sure the Bussard isn't practical at near lightspeed because the power possible from a set amount of hydrogen is less than the drag from gathering it after a certain speed.
 I'd hate to hit a speck of dust at .99c.
 I'm not sure why time dialation would make it implausible. It would actually make it more plausible. If you can go something like .993c, you can travel 100 light years in 10 years. Time isn't "percieved" as being less for travelers. It is less.
« Last Edit: 08/03/2011 11:44 am by Nomadd »
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline Celebrimbor

  • Regular
  • Full Member
  • ****
  • Posts: 414
  • Bystander
  • Brinsworth Space Centre, UK
  • Liked: 12
  • Likes Given: 6
Re: 99% of Light speed
« Reply #4 on: 08/03/2011 12:00 pm »

Online Chris Bergin

Re: 99% of Light speed
« Reply #5 on: 08/03/2011 12:19 pm »
     At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard. 

This always messes with my head ;D

So would they only age 14 years, over those 100 years? And if - dismissing the slowing down time etc - they carried out the return trip, they'd arrive back on Earth 28 years older than when they set out, but 200 years would have passed on Earth?
Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Offline Celebrimbor

  • Regular
  • Full Member
  • ****
  • Posts: 414
  • Bystander
  • Brinsworth Space Centre, UK
  • Liked: 12
  • Likes Given: 6
Re: 99% of Light speed
« Reply #6 on: 08/03/2011 12:36 pm »
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.

Unstable particles moving at relativistic speeds in particle accelerators increase their lab-frame half life and so they don't decay as quickly as you might expect.
« Last Edit: 08/03/2011 12:37 pm by Celebrimbor »

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10974
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1257
  • Likes Given: 724
Re: 99% of Light speed
« Reply #7 on: 08/03/2011 01:26 pm »
I gotta speeding ticket last year.  If my calculations are correct, I was only going  well under .0000001% the speed of light.  The officer didn't buy my explanation.

Gotta go.
Sometimes I just flat out don't get it.

Online Chris Bergin

Re: 99% of Light speed
« Reply #8 on: 08/03/2011 01:43 pm »
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.

Unstable particles moving at relativistic speeds in particle accelerators increase their lab-frame half life and so they don't decay as quickly as you might expect.

Wow. Well there's one solution for living to see York promoted. I reckon we've got a good chance in 2173-74 season ;)
Support NSF via L2 -- Help improve NSF -- Site Rules/Feedback/Updates
**Not a L2 member? Whitelist this forum in your adblocker to support the site and ensure full functionality.**

Offline Celebrimbor

  • Regular
  • Full Member
  • ****
  • Posts: 414
  • Bystander
  • Brinsworth Space Centre, UK
  • Liked: 12
  • Likes Given: 6
Re: 99% of Light speed
« Reply #9 on: 08/03/2011 02:06 pm »
The OP's questions are in the context of human colonisation of other stars.

But if humans became capable of generating the kind of power to move themselves around at 0.99c, then wouldn't we be more-than-capable of living in space permanently i.e. mining asteroids and Oort objects etc.?  If we can do that then why the rush to get to another star?

If you're talking about getting an unmanned scientific probe to another star as soon as possible, then 0.99c makes a bit more sense - but not much.  What's wrong with 0.5c for instance?
« Last Edit: 08/03/2011 02:11 pm by Celebrimbor »

Offline D_Dom

  • Global Moderator
  • Full Member
  • *****
  • Posts: 655
  • Liked: 481
  • Likes Given: 152
Re: 99% of Light speed
« Reply #10 on: 08/03/2011 03:30 pm »
I reckon we've got a good chance in 2173-74 season ;)

Thanks for a glimpse into the future Chris, one of your finest attributes has to be your ability to think ahead  8)
Space is not merely a matter of life or death, it is considerably more important than that!

Offline Joris

  • Full Member
  • ***
  • Posts: 372
  • Liked: 24
  • Likes Given: 3
Re: 99% of Light speed
« Reply #11 on: 08/03/2011 03:37 pm »
Blue skies research will offer beyond the standard-model solutions for interstellar travel one day.
That day will come sooner than the day we will be able to travel at relativistic speeds by conventional means. (conventional should be taken with a grain of salt here  ;))
JIMO would have been the first proper spaceship.

Offline kevin-rf

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8823
  • Overlooking the path Mary's little Lamb took..
  • Liked: 1318
  • Likes Given: 306
Re: 99% of Light speed
« Reply #12 on: 08/03/2011 04:04 pm »
Can someone remind me again. To date, what is the largest thing that has been accelerated to that speed? Heavy Atomic Nuclei?

Just to put this in perspective...
If you're happy and you know it,
It's your med's!

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
Re: 99% of Light speed
« Reply #13 on: 08/03/2011 04:26 pm »
We are about theoretically .05c, so we would be lucky to get 1 percent speed of light. Without some quantum leap in physics (no pun intenteded).
Regards
Robert
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Lampyridae

  • Veteran
  • Senior Member
  • *****
  • Posts: 2641
  • South Africa
  • Liked: 949
  • Likes Given: 2056
Re: 99% of Light speed
« Reply #14 on: 08/03/2011 04:50 pm »
This is probably where you get stuff like gravity accelerators, with powerful Kardashev-II civilisations chucking around planet-sized masses. One idea for a gravity-based accelerator was a superdense donut rapidly rotating around the toroidal axis (ie twisting). It could be spun up electromagnetically, offering the most energy bang for the buck but requires a huge initial energy investment. A small spacecraft enters, is swept up and goes whizzing out the "barrel." All with zero acceleration. It's the gravity slingshot taken to its logical extreme. It could even be an artificial, donut-shaped collapsar (I recall reading that such things were possible... as are toroidal planets under very unique conditions...). Robert Forward had other interesting ideas for reactionless drives that were plausible under modern physics (although not necessarily easy to build...)

My own version would probably rather involve a series of superdense rings, rotating as described, more like a gravitational coilgun than anything else.

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
Re: 99% of Light speed
« Reply #15 on: 08/03/2011 06:44 pm »
We are about theoretically .05c, so we would be lucky to get 1 percent speed of light. Without some quantum leap in physics (no pun intenteded).
Regards
Robert


We already can do much better then 1% speed of light with our present knowledge of physics.

With a thermonuclear Orion 8 to 10% c can be achieved.

http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

If we could manufacture antimatter in large amounts 50 to 80% c would be possible.

On the Bussard ramjet it also could act as a brake if the gas is captured and stored vs burned.
« Last Edit: 08/03/2011 06:47 pm by Patchouli »

Offline Rocket Science

  • Senior Member
  • *****
  • Posts: 10586
  • NASA Educator Astronaut Candidate Applicant 2002
  • Liked: 4548
  • Likes Given: 13523
Re: 99% of Light speed
« Reply #16 on: 08/03/2011 06:52 pm »
Still science fiction from the mid-century... nice picture though :)
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Celebrimbor

  • Regular
  • Full Member
  • ****
  • Posts: 414
  • Bystander
  • Brinsworth Space Centre, UK
  • Liked: 12
  • Likes Given: 6
Re: 99% of Light speed
« Reply #17 on: 08/03/2011 07:08 pm »
Can someone remind me again. To date, what is the largest thing that has been accelerated to that speed? Heavy Atomic Nuclei?

Just to put this in perspective...

Yeah, I think its lead ions in the large hadron collider. But since we're talking relativity, that collider is designed to accelerate individual protons until their mass exceeds that of a lead nucleus...

Offline Andrew_W

  • Full Member
  • ****
  • Posts: 754
  • Rotorua, New Zealand
    • Profiles of our future in space
  • Liked: 17
  • Likes Given: 12
Re: 99% of Light speed
« Reply #18 on: 08/03/2011 07:25 pm »
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.

Pardon? The equation Alexw gives above includes velocity as a fraction of c, but not acceleration.
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline Nomadd

  • Senior Member
  • *****
  • Posts: 8840
  • Lower 48
  • Liked: 60430
  • Likes Given: 1305
Re: 99% of Light speed
« Reply #19 on: 08/03/2011 07:28 pm »
That's right, its the accelration not the velocity that does it. And remember, you don't need to accelerate in a straight line, you can go in a circle.

Unstable particles moving at relativistic speeds in particle accelerators increase their lab-frame half life and so they don't decay as quickly as you might expect.

 I take it you're refering to objects at different levels of a gravitational field. The difference does cause time dialtion but a coasting object at .99c has the same effect.
 And atoms in a centrifuge don't experience time dialation because of their acceleration. Differences in gravitational potential can cause time dialation, not gravitational strength. The centrifuge objects are dialated because of their speed. The same as ones in a linear accelerator are.
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline Celebrimbor

  • Regular
  • Full Member
  • ****
  • Posts: 414
  • Bystander
  • Brinsworth Space Centre, UK
  • Liked: 12
  • Likes Given: 6
Re: 99% of Light speed
« Reply #20 on: 08/04/2011 06:31 am »
I was replying to Chris's comment about coming back to earth finding it had aged faster than you. That requires following a closed loop in space, hence acceleration. 

Online MP99

Re: 99% of Light speed
« Reply #21 on: 08/04/2011 12:13 pm »
This refers to the "twins paradox".

AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow.

It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)

cheers, Martin

Offline Nomadd

  • Senior Member
  • *****
  • Posts: 8840
  • Lower 48
  • Liked: 60430
  • Likes Given: 1305
Re: 99% of Light speed
« Reply #22 on: 08/04/2011 12:16 pm »
 This whole thread is making me feel older. Is it still too late to go back to the church of Newton?
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline Patchouli

  • Senior Member
  • *****
  • Posts: 4490
  • Liked: 253
  • Likes Given: 457
Re: 99% of Light speed
« Reply #23 on: 08/04/2011 06:00 pm »
This refers to the "twins paradox".

AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow.

It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)

cheers, Martin


That is true an atomic clock on a vehicle in LEO such as the Shuttle does end up several milliseconds behind one left on Earth.

Another odd thing an atomic clock on a high orbit satellite such as a GPS sat runs slightly faster because it's not moving that fast but is outside of most of Earth's gravity well which also has a very slight time dilation effect.

How ever slight it is they must compensate for it in both cases.






Offline Andrew_W

  • Full Member
  • ****
  • Posts: 754
  • Rotorua, New Zealand
    • Profiles of our future in space
  • Liked: 17
  • Likes Given: 12
Re: 99% of Light speed
« Reply #24 on: 08/04/2011 07:02 pm »
This refers to the "twins paradox".

AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow.

It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)

cheers, Martin

If the time dilation happens during acceleration, rather than while the ship is coasting if one ship accelerates to 0.99c, coasts for zero time, then decelerates, then reverse the proses and returns to Earth, another ship does the same but coasts for a year (ship time) before undertaking identical accelerations (including a year of coasting) to return to Earth, how much time has passed on ship and on Earth in each instance?

Edit: To keep it simple maybe just the difference between the two ships times and Earth time,
« Last Edit: 08/04/2011 07:32 pm by Andrew_W »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline Tass

  • Full Member
  • ***
  • Posts: 370
  • Liked: 89
  • Likes Given: 208
Re: 99% of Light speed
« Reply #25 on: 08/05/2011 06:29 pm »
It is all a question of reference frames. Both views are correct to an extend.

The important thing is that you predict the right time dilation, not whether you say it was due to the acceleration or the speed.

In special relativity it is due to the speed. "But velocity is relative, the moving twin might say that he is stationary and the other is moving". Yeah, but in order for them to meet up one has to accelerate, and strictly speaking you can no longer use special relativity then.

Offline gbaikie

  • Full Member
  • ****
  • Posts: 1592
  • Liked: 49
  • Likes Given: 5
Re: 99% of Light speed
« Reply #26 on: 08/05/2011 08:09 pm »
Is it possible to build a vehicle that can accelerate to .99 C?

How would we go about doing something like this?

If at all possible, how many centuries or millennia is it before this can be accomplished?

Could a Bussard scramjet do it?

How large would a laser/maser/gaser have to be to get the craft up to such speed?

How long would it take from the crew's perspective to cross the galaxy?

How big would the craft be? I imagine a lot of fuel would be required even if you could gather propellant along the way - Bussard scramjet. What kind of fuel would be needed?

Would such a vessel help establish a galactic civilization? Or would time dilation make implausible?

What would it look like?

Are any sort of warp drives completely impossible? If so, which of the following would best for interstellar travel: beamed propulsion, matter/antimatter reaction, Bussard scramjet, or something else?

This very fascinating for me.

One could probably make a nano spaceship which could reach .99 C decades or centuries before something on a larger scale.
A spaceship weighing less than a gram would have many advantages.
The biggest advantage would it could be designed to withstand very high gees- probably well over a 1000 gees.
At 1000 gees or 1000 times 9.8 m/s/s [about 10,000 m/s/s or 10 km/sec/sec] to reach about 300,000 km/sec requires around 30,000 seconds [less than 4 days]. Pluto is about 5 light minutes from earth.*
So generally, one probably start beyond Pluto, and by the time you reached Sun distant need to be going around 1/2 the speed of light, and need the rest of our system to push up to .99 C.

If you wanted a much larger spacecraft, say 1 kg or two, one similarly should focus on spacecraft being able to withstand very high gees. Perhaps you push and pull the vehicle or accelerate the entire vehicle- perhaps indicating using some kind magnetic means of propulsion.

Edit: One could also send a spacecraft in pieces which are reassemble once they have finished accelerating.
Many common things can withstand over 1000 gees, an empty soda can, a baseball, ect- whereas large structures or human bodies can not- or I should say makes it much more complicated/difficult. Anyhow I meant over 1000 gees, perhaps 10 or even 100 times more than 1000 gees.

*I meant Pluto is 5 hours not minutes.
« Last Edit: 08/05/2011 09:11 pm by gbaikie »

Offline scienceguy

  • Regular
  • Full Member
  • ****
  • Posts: 836
  • Lethbridge, Alberta
  • Liked: 155
  • Likes Given: 279
Re: 99% of Light speed
« Reply #27 on: 08/05/2011 08:20 pm »
Don't you mean that Pluto is 5 light hours from earth?
e^(pi*i) = -1

Offline Andrew_W

  • Full Member
  • ****
  • Posts: 754
  • Rotorua, New Zealand
    • Profiles of our future in space
  • Liked: 17
  • Likes Given: 12
Re: 99% of Light speed
« Reply #28 on: 08/05/2011 08:58 pm »
I don't see how interstellar micro space probes could work, every atom they collided with would be a cosmic ray.
« Last Edit: 08/05/2011 08:59 pm by Andrew_W »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline gbaikie

  • Full Member
  • ****
  • Posts: 1592
  • Liked: 49
  • Likes Given: 5
Re: 99% of Light speed
« Reply #29 on: 08/05/2011 11:25 pm »
I don't see how interstellar micro space probes could work, every atom they collided with would be a cosmic ray.

Space is big. If your cross section is less than one mm- the chance is 100 times less than if it was 1 cm and 1 million times less than square meter.
Also can send 10 spacecraft instead of one.
Big items [compared to atoms] may have crossed the galaxy:
http://www.fourmilab.ch/documents/OhMyGodParticle/
The above article also mentions as go closer to light:
"Finally, let's consider the length contraction in the direction of motion which results from the Lorentz transformation:"

And wiki:
"Outer space is the closest natural approximation of a perfect vacuum. It has effectively no friction, allowing stars, planets and moons to move freely along their ideal orbits. However, even the deep vacuum of intergalactic space is not devoid of matter, as it contains a few hydrogen atoms per cubic meter"
http://en.wikipedia.org/wiki/Outer_space

I would say if you had a sheet of metal which meter square [and 1 meter cross section] it would hit less atoms than a one cubic meter of metal- same cross section passing thru space. Regardless of velocity. And as you say all atoms may behave similar to cosmic rays as approach light speed.
Cosmic rays can pass thru solid material. Not only is space big but matter has a lot of space in it.

So say you have a spacecraft with cross section of less than 1 mm, comprised of billions of atoms, and perhaps as much as 1 mm in length, it has less than a 1/billionth of chance to hit a atom as compared to an object bigger than 1 meter cube. If your spacecraft in the same cubic mm as an atom in space- it won't necessarily hit the spacecraft. And has much higher chance of that atom hitting it if instead the spacecraft  was a cubic meter or larger.

An atom in space hitting an atom of your spacecraft doesn't need to be very significant- though perhaps you lose velocity and lose a atom or two. Maybe the spacecraft could still suffer say 100 hits. And survive better than 1 cube meter spacecraft being hit by significantly more the than 100 billion hits. Therefore at velocity we currently travel at the nano spacecraft should receive less damage as compared to "normal spacecraft". And at velocity approaching light speed where all object are like cosmic rays, a nano spacecraft should hit less than any 1 cubic mm part of first 1 meter of the spacecraft. Meaning that if atoms in space would have good chance of destroying a nano spacecraft, it will without any doubt destroy vehicles larger than 1 meter cube or cubic foot or 1000 cubic meters. 
« Last Edit: 08/05/2011 11:38 pm by gbaikie »

Offline alexw

  • Full Member
  • ****
  • Posts: 1230
  • Liked: 4
  • Likes Given: 2
Re: 99% of Light speed
« Reply #30 on: 08/06/2011 04:22 am »
This refers to the "twins paradox".
AIUI, in special relativity (ie if not accelerating), then a crew member looking back at Earth would see it receding at high speed, and therefore it's clocks running slowly. (It's all "relative", you see.) Thus the paradox - each sees the other's clocks as running slow.
   It is the acceleration undertaken by the ship which means duration is shorter for the twin in the ship's crew than the one left behind on Earth. Apparently. (I never did quite grasp the reason myself.)
cheers, Martin
    You're correct to point out that the acceleration is relevant to the question of the Twin's Paradox.
     The time dilation is due to the velocity, not the acceleration (and an earlier poster was quite correct to point out that my choice of the word "perceive" is misleading -- time for the spacecraft's occupants really /does/ go more slowly.) The Twin's Paradox is in some sense founded on the "Principle of Relativity", which underlies the Special Theory -- the folks /coasting/ in the spaceship, and the folks sitting back on Earth, are both in inertial frames, so why is there a difference? Who's to say who's clock runs more slowly? But the spaceship and Earth are /not/ equivalent -- the spaceship accelerated at times, and those non-inertial frames of reference are not equivalent.  (Hmmm, not sure if I'm explaining this in a way at all helpful.)

BTW, Special Relativity can absolutely deal with acceleration -- you just use an (infinite) series of instantaneous co-moving inertial reference frames :) It's simpler than it sounds, but the equations do get uglier.
   
   -Alex

Offline alexw

  • Full Member
  • ****
  • Posts: 1230
  • Liked: 4
  • Likes Given: 2
Re: 99% of Light speed
« Reply #31 on: 08/06/2011 04:44 am »
     At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard. 
This always messes with my head ;D
So would they only age 14 years, over those 100 years? And if - dismissing the slowing down time etc - they carried out the return trip, they'd arrive back on Earth 28 years older than when they set out, but 200 years would have passed on Earth?
      kiloyears. The galaxy is rather big :)

      Yes, if they returned to Earth, they'd be only 28000 years older, while those on Earth would be 200000 years older. Travel at relativistic speeds *is* a time machine, just that it only goes /forward/ --- as it is for those on Shuttle, on infinitesimal scales.

    -Alex

Offline hydra9

  • Full Member
  • ***
  • Posts: 349
  • Liked: 16
  • Likes Given: 6
Re: 99% of Light speed
« Reply #32 on: 08/09/2011 06:30 am »
I'd place my bets on a relativistic star ship with a magnetic sail powered by hundreds or perhaps thousands of large solar orbiting particle beam accelerators.

The magnetic sail would also be able to act as a parachute  decelerating the vessel towards the target star system.

However, such star voyages would probably be one way trips until the target star colony is able to build enough particle beam accelerators in its new star system to send astronauts back to Sol.

Marcel F. Williams

Offline Tnarg

  • Full Member
  • *
  • Posts: 102
  • Liked: 6
  • Likes Given: 0
Re: 99% of Light speed
« Reply #33 on: 08/09/2011 11:32 am »
The closer you get to the speed of light the harder it is.  It would be 100 times easier to go at .5c instead of .99c.  You lose the slowing down time but if we are to colonize the galactic it will be one planet at a time.  If we can find a planet with in 15 LY then we could get there in 26 years ship time at 0.5c.  Which is do able.  But would be easier with some kind of hibernation or freezing.  Failing that growing new people and having robots rise them would be easier then 'teleporting consciousness'

Smaller and faster survey ships would be needed but even these a have no need to go at anywhere near 0.99c.

Offline Tass

  • Full Member
  • ***
  • Posts: 370
  • Liked: 89
  • Likes Given: 208
Re: 99% of Light speed
« Reply #34 on: 08/09/2011 12:47 pm »
but if we are to colonize the galactic it will be one planet at a time. If we can find a planet with in 15 LY then we could get there in 26 years ship time at 0.5c.

When we have the infrastructure and technology for interstellar travel we won't need planets at all, and when you already call space you home a generation ship is no problem. Load up on nuclear power (be it fission or fusion) and you entire "country" takes off at a leisurely pace.

We might want to send stuff to other stars fast for exploration, science and basic curiosity. (Are there life?)

At .5c It would take 41 years to get data back from a probe to an interesting planet. Remotely doable.

Offline DLR

  • Full Member
  • ****
  • Posts: 497
  • Liked: 20
  • Likes Given: 0
Re: 99% of Light speed
« Reply #35 on: 08/30/2011 07:20 am »
I think our best near-term (~22nd century) bet to achieve relativistic velocities is to use beamed propulsion. Antimatter would be a possibility as well, but the storage problem has still not been solved and producing even small quantities takes horrendous amounts of energy. Contrary to antimatter, laser sails are thorougly understood.

For manned trips to the stars, unmanned one-way cargo vessels with magsail brakes would be launched first to the target star, setting up self-replicating robotic factories which produce a laser array for the deceleration and return of a manned starship. Once the signal that the laser array is online has arrived (it would now be the 23rd century depending on the destination), a manned spacecraft is sent. If accelerated to 0.5c by the lasers, A-Centauri would be a mere 7.6 years away ship-time (thanks to time dilation).

Magsail deceleration has disadvantages. It doesn't take long to go from, say, 0.5c to 0.1c, but the deceleration from 0.1 to 0.001c or so takes ages. We're looking at 12 to 18 years here, depending on the magsail, covering a distance of only a light year. Acceptable for robotic probes, but probably not manned starships. So a manned mission to A-Cen would most likely use lasers on both ends. They have to be prepositioned first, but by the time we go to the stars, robotics should be advanced enough to allow for the autonomous construction of such an array from in-situ resources.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2431
  • Likes Given: 13606
Re: 99% of Light speed
« Reply #36 on: 08/30/2011 08:28 am »
     At 0.99c, gamma = 1/sqrt(1-(v/c)^2) ~=~ 7, so 100k light years for the galactic diameter would take about 100k years and would be perceived as 14k years passage of time for those onboard. 

This always messes with my head ;D

So would they only age 14 years, over those 100 years? And if - dismissing the slowing down time etc - they carried out the return trip, they'd arrive back on Earth 28 years older than when they set out, but 200 years would have passed on Earth?

That k implies a factor of a 1000. Barring the development of something to make people virtually immortal you could only survive the journey in suspended animation by missing the in between bits.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 4286
  • Liked: 887
  • Likes Given: 201
Re: 99% of Light speed
« Reply #37 on: 08/30/2011 10:30 am »

Magsail deceleration has disadvantages. It doesn't take long to go from, say, 0.5c to 0.1c, but the deceleration from 0.1 to 0.001c or so takes ages.

I wonder if you could use the magsail to collect propellant during deceleration so that once the speed was too slow for the magsail to be effective you would have full tanks to complete the deceleration by more conventional electric propulsion.

Offline DLR

  • Full Member
  • ****
  • Posts: 497
  • Liked: 20
  • Likes Given: 0
Re: 99% of Light speed
« Reply #38 on: 08/30/2011 03:26 pm »
I'm falling in love with the idea of using laser-pushed lightsails for rapid interstellar travel. They seem to be much more practical than fusion or antimatter rockets.

Fusion rockets are limited to ~0.1-0.2c and that only with staggering mass ratios, while lightcrafts could achieve relativistic speeds using currently understood engineering.

Assuming a 68km diameter Al2O3 (Sapphire) sail with a mass of 226kg per km^2, a reflectivity of 26%, a thermal limit of 34MW per km^2 (as proposed by Landis, 1999), a structural support mass of 1.3*Sail Mass and a payload mass of 2000t (small manned interstellar craft or large robotic probe). A 21 Petawatt laser with a 50km aperture could accelerate that baby to 0.65c within 317 days (~1g acceleration), if my calculations are correct.

21 Petawatts are 21,000 Terawatts, truly a staggering amount of power (Earth's average energy consumption rate is 15TW), but assuming an array of solar-pumped lasers with 30% efficiency orbiting at 0.1 AU, the collector diameter necessary would "only" be 800km (using the formula found on page 93 of Greogry Matloff's book "Deep Space Probes"). This could be split up into several smaller satellites which would focus their beams on a common aperture.

While out of reach today, given highly autonomous self-replicating mining and manufacturing machinery is availible, it may become affordable in the 22nd century or so.

In the near future, smaller, slower probes (0.1c) could be sent to the stars using more modest arrays, for example a combination of several SPS satellites in Earth orbit.
« Last Edit: 08/30/2011 03:40 pm by DLR »

Offline DLR

  • Full Member
  • ****
  • Posts: 497
  • Liked: 20
  • Likes Given: 0
Re: 99% of Light speed
« Reply #39 on: 08/30/2011 03:33 pm »

Magsail deceleration has disadvantages. It doesn't take long to go from, say, 0.5c to 0.1c, but the deceleration from 0.1 to 0.001c or so takes ages.

I wonder if you could use the magsail to collect propellant during deceleration so that once the speed was too slow for the magsail to be effective you would have full tanks to complete the deceleration by more conventional electric propulsion.

The density of the interstellar medium is extremely low.

Zubrin proposed carrying a small fusion rocket along for the last leg. That would reduce the overall deceleration time to 12 years or so.
« Last Edit: 08/30/2011 04:02 pm by DLR »

Offline 93143

  • Senior Member
  • *****
  • Posts: 3054
  • Liked: 312
  • Likes Given: 1
Re: 99% of Light speed
« Reply #40 on: 08/30/2011 07:26 pm »
That's a Bussard ramjet, but with the drag as a desireable characteristic rather than something to work around.

It could work, perhaps, if you could burn protium in a fusion reactor (Bussard et al. claimed they had found a way to catalyze p-p fusion, but the description was ambiguous and no one is quite sure what it was...).

Conventional electric propulsion won't help much with deceleration from interstellar velocity - but of course having full tanks for in-system maneuvering, without having had to bring the whole load along, could be quite helpful...  one issue is that if you don't use the collected propellant to brake from interstellar speed, it increases the spacecraft's mass and extends the time required to brake...

Offline DLR

  • Full Member
  • ****
  • Posts: 497
  • Liked: 20
  • Likes Given: 0
Re: 99% of Light speed
« Reply #41 on: 09/01/2011 02:38 pm »
I don't think that you would collect a useful amount of hydrogen for your electric thrusters while slowing down using the magsail.
I once read that compressing the entire column of interstellar medium between the Sun and Alpha Centauri to a normal density (air I presume), you would get a layer only a micrometer or so thick ...

Offline qraal

  • Full Member
  • *
  • Posts: 183
  • Liked: 66
  • Likes Given: 22
Re: 99% of Light speed
« Reply #42 on: 09/07/2011 06:19 am »
That's a Bussard ramjet, but with the drag as a desireable characteristic rather than something to work around.

It could work, perhaps, if you could burn protium in a fusion reactor (Bussard et al. claimed they had found a way to catalyze p-p fusion, but the description was ambiguous and no one is quite sure what it was...).

It's not ambiguous at all. Bussard meant CNO Cycle catalyzed fusion, as described in Daniel Whitmire's paper back in 1975...

"Relativistic Spaceflight and the Catalytic Nuclear Ramjet", Acta Astronautica, 2, 497 (1975).

Available from Askmar.com... Catalytic Nuclear Ramjet

We discussed this a few years ago and Askmar.com put it up in the mean time, with updated formatting.


Offline aquanaut99

  • Full Member
  • ****
  • Posts: 1049
  • Liked: 33
  • Likes Given: 0
Re: 99% of Light speed
« Reply #43 on: 09/07/2011 06:34 am »
All you guys do realize that any solid object travelling at that speed is also the most deadly weapon of mass destruction in the known universe, right?

The R-bomb. More effective than antimatter. And by the time you see it coming, it's almost on top of you. Impossible to intercept (due to light lag you never see it where it really is), and even if you do blow it up, the particle/vapor cloud is still there travelling at nearly the same velocity and with nearly the same kinetic energy.

Charles Pellegrino (I think it was) wrote a novel some years back called "Killing Star" where Earth's population is wiped out through relativistic bombardment by a hostile alien species. One of the few survivors is later captured by the invaders who tell him the reason for the attack: Once humans had developped relativistic travel they became too dangerous to have as neighbours because every relativistic starship is simultaneously an undetectable and unstoppable WMD. So they struck first in the ultimate preemtive attack...

Something to think about.

Unfortunately, the book is almost impossible to find nowadays. Too bad, because Pellegrino actually had an excellent concept study of what such a vessel might look like ("Valkyrie", google it up. It was also used in the Avatar movie. Tho I think Valkyrie was limited to .92c).
« Last Edit: 09/07/2011 06:58 am by aquanaut99 »

Offline 93143

  • Senior Member
  • *****
  • Posts: 3054
  • Liked: 312
  • Likes Given: 1
Re: 99% of Light speed
« Reply #44 on: 09/07/2011 07:09 am »
That's a Bussard ramjet, but with the drag as a desireable characteristic rather than something to work around.

It could work, perhaps, if you could burn protium in a fusion reactor (Bussard et al. claimed they had found a way to catalyze p-p fusion, but the description was ambiguous and no one is quite sure what it was...).

It's not ambiguous at all. Bussard meant CNO Cycle catalyzed fusion, as described in Daniel Whitmire's paper back in 1975...

"Relativistic Spaceflight and the Catalytic Nuclear Ramjet", Acta Astronautica, 2, 497 (1975).

Available from Askmar.com... Catalytic Nuclear Ramjet

We discussed this a few years ago and Askmar.com put it up in the mean time, with updated formatting.



Okay.  I'm not an expert in this field and had seen others wonder what precisely this "Bi-Cycle" actually was (at least one person was led by the nomenclature to believe bismuth might be involved).  I know what the CNO cycle is...

I once read that compressing the entire column of interstellar medium between the Sun and Alpha Centauri to a normal density (air I presume), you would get a layer only a micrometer or so thick ...

Almost exactly a micrometre, according to my calculations, assuming a liquid hydrogen density of 70 kg/m³ (the Local Fluff has a density of 0.1 hydrogen atoms per cc, and Alpha Centauri is 4.37 light years away)...

How big is an interstellar magsail again?
« Last Edit: 09/07/2011 07:31 am by 93143 »

Offline MarkZero

  • Member
  • Posts: 18
  • Finland
  • Liked: 1
  • Likes Given: 0
Re: 99% of Light speed
« Reply #45 on: 09/07/2011 08:16 am »
All you guys do realize that any solid object travelling at that speed is also the most deadly weapon of mass destruction in the known universe, right?

The R-bomb. More effective than antimatter. And by the time you see it coming, it's almost on top of you. Impossible to intercept (due to light lag you never see it where it really is), and even if you do blow it up, the particle/vapor cloud is still there travelling at nearly the same velocity and with nearly the same kinetic energy.

Charles Pellegrino (I think it was) wrote a novel some years back called "Killing Star" where Earth's population is wiped out through relativistic bombardment by a hostile alien species. One of the few survivors is later captured by the invaders who tell him the reason for the attack: Once humans had developped relativistic travel they became too dangerous to have as neighbours because every relativistic starship is simultaneously an undetectable and unstoppable WMD. So they struck first in the ultimate preemtive attack...

Something to think about.

Unfortunately, the book is almost impossible to find nowadays. Too bad, because Pellegrino actually had an excellent concept study of what such a vessel might look like ("Valkyrie", google it up. It was also used in the Avatar movie. Tho I think Valkyrie was limited to .92c).

Something to think about maybe, but not something that should stop us from building near light speed interstellar craft.

I don't think there are any advanced aliens close enough for them to have even detected humanity's existence yet or in the "near" future (couple of hundred years at least) by conventional (light-speed/sublight) means, simply for the reason that if there were, we probably would have also already detected them.

Of course if some advanced aliens have FTL capabilities they could have detected our presence from further away by using a probe, but then they would also be able to detect and intercept an R-bomb before it is even launched without needing to resort to such a genocidal pre-emptive strike.

There is also the possibility that aliens would send an R-bomb as a pre-emptive strike to any life sustaining body they detect, in which case, because Earth has had life for some time, an R-bomb might already be well on its way. Which only is another reason why humanity should establish off-world colonies asap.
« Last Edit: 09/07/2011 08:22 am by MarkZero »

Offline mlorrey

  • Member
  • Senior Member
  • *****
  • Posts: 2173
  • International Spaceflight Museum
  • Grantham, NH
  • Liked: 23
  • Likes Given: 5
Re: 99% of Light speed
« Reply #46 on: 09/07/2011 08:22 am »
Magsails should have a magnetic field the size of the moon, tho this will vary depending on velocity and local interstellar magnetic flux density.

As for calculating the interstellar medium, you need to  look at how dense the solar wind is when it hits the heliopause, however, there is another way to go about it: operate your ramjet closer, say, between Earth and Venus, and have its jet point slightly outward, so that it can accelerate to a much higher speed while maintaining its distance from the sun. You'll get a much higher velocity from the higher density of the solar wind that close in, plus the occasional boost from CME's

Wikipedia says: "In cool, dense regions of the ISM, matter is primarily in molecular form, and reaches number densities of 106 molecules cm−3. In hot, diffuse regions of the ISM, matter is primarily ionized, and the density may be as low as 10−4 ions cm−3" So based on these limits, you have a rather broad range of estimated amount of hydrogen you could scoop up in the interstellar medium. That said, the heliopause is less than 1 light year out, but more than the distance the Voyager probes have gone (about 10 billion miles), so there is plenty of more dense solar wind for a bussard ramjet to suck on before it reaches the interstellar medium.

Also, "Radio observations of the 21 cm interstellar line suggested density of neutral hydrogen on the order of 0.7 per cubic centimeter, considerably higher than the value obtained from measurements of Lyman alphalpha absorption in the spectra of nearby early type stars, namely about 0.1 per cubic centimeter." http://web.mit.edu/space/www/helio.review/axford.suess.html

So using the 21cm radio line suggest seven times higher density than the Lyman alpha measurement that qraal bases his calcs on.
VP of International Spaceflight Museum - http://ismuseum.org
Founder, Lorrey Aerospace, B&T Holdings, ACE Exchange, and Hypersonic Systems. Currently I am a venture recruiter for Family Office Venture Capital.

Offline qraal

  • Full Member
  • *
  • Posts: 183
  • Liked: 66
  • Likes Given: 22
Re: 99% of Light speed
« Reply #47 on: 09/07/2011 11:56 am »
Magsails should have a magnetic field the size of the moon, tho this will vary depending on velocity and local interstellar magnetic flux density.

So using the 21cm radio line suggest seven times higher density than the Lyman alpha measurement that qraal bases his calcs on.

Wasn't me. Was someone else in this thread, though I have computed mag-sail performance for my blog and "Project Icarus".

Dana Andrews has suggested to me in personal correspondance about mag-sails that because the ISM encounters a very rapidly changing magnetic field around a moving mag-sail, it should become ionized from the encounter, thus creating more ion drag and providing an extra energy sink in the drag process. Thus I think mag-sails are an excellent way of braking from interstellar speeds.

Gerald Nordley has recently put up his old presentation materials on Mass-beams, which features a mag-sail in his early mass-beam design...

Mass-Beam Presentation 1993

...still the best way to hit relativistic speeds IMO, absent a viable ramjet.

Offline kevin-rf

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8823
  • Overlooking the path Mary's little Lamb took..
  • Liked: 1318
  • Likes Given: 306
Re: 99% of Light speed
« Reply #48 on: 09/07/2011 12:34 pm »
Unfortunately, the book is almost impossible to find nowadays.
http://www.amazon.com/Killing-Star-Charles-Pellegrino/dp/0380770261/ref=sr_1_6?ie=UTF8&qid=1315398673&sr=8-6

Looking at the prices, a bit of a collectors item though.
If you're happy and you know it,
It's your med's!

Offline aquanaut99

  • Full Member
  • ****
  • Posts: 1049
  • Liked: 33
  • Likes Given: 0
Re: 99% of Light speed
« Reply #49 on: 09/07/2011 01:32 pm »
Looking at the prices, a bit of a collectors item though.

Thanks, but that's far too much for a paperback novel (for me at least).

Just to illustrate the point that any relativistic vehicle is also an RKV (relativistic kill vehicle or R-bomb) and simultaneously the most destructive WMD known:

1 kg of matter accelerated to .99c impacting Earth has a TNT equivalent of 132 Megatons (almost 2.5 times the Tsar Bomba, the largest nuke ever detonated).

Compare this to 1 kg of matter-antimatter annihilation, which has a TNT equivalent of "only" 21.5 Megatons...

And yes, any relativistic Starship is also an RKV. Infact, an RKV is much easier to build, since it doesn't have to carry fuel to slow down at the end of the voyage...
« Last Edit: 09/07/2011 01:34 pm by aquanaut99 »

Offline gospacex

  • Senior Member
  • *****
  • Posts: 3024
  • Liked: 543
  • Likes Given: 604
Re: 99% of Light speed
« Reply #50 on: 09/07/2011 02:34 pm »
The R-bomb. More effective than antimatter. And by the time you see it coming, it's almost on top of you. Impossible to intercept (due to light lag you never see it where it really is)

Don't be too fast in writing off the shield in the eternal "sword vs shield" competition!

Civilization which can build missiles able to accelerate to 0.9c ought to be able to write software which can easily account for detection lag. It's actually a trivial problem - building long-range detection radars is a more difficult one, but doable even with our current tech!

A missile at 0.9c practically doesn't maneuver. Predicting its trajectory is easy.

Quote
and even if you do blow it up, the particle/vapor cloud is still there travelling at nearly the same velocity and with nearly the same kinetic energy.

but this cloud is heated to many millions of degrees K and therefore rapidly (thousands km/s) expanding.

RKV won't survive even a millimeter thick tin foil "armor".

Offline qraal

  • Full Member
  • *
  • Posts: 183
  • Liked: 66
  • Likes Given: 22
Re: 99% of Light speed
« Reply #51 on: 09/10/2011 09:37 pm »
Just to illustrate the point that any relativistic vehicle is also an RKV (relativistic kill vehicle or R-bomb) and simultaneously the most destructive WMD known:

1 kg of matter accelerated to .99c impacting Earth has a TNT equivalent of 132 Megatons (almost 2.5 times the Tsar Bomba, the largest nuke ever detonated).

Compare this to 1 kg of matter-antimatter annihilation, which has a TNT equivalent of "only" 21.5 Megatons...

And yes, any relativistic Starship is also an RKV. Infact, an RKV is much easier to build, since it doesn't have to carry fuel to slow down at the end of the voyage...

Maneuvers like a battleship being dragged sideways through mud though. The targeting system would need to be incredibly accurate.

I suspect an artificially enhanced Zodiacal dust cloud would make a more than adequate defense against R-bombs. Of course one needs to set it up long before "the enemy" starts firing off R-bombs, because there's not a lot of warning when it's on its way.

Tom Ligon wrote a short-story which described the defense perimeter set up against an incoming R-bomb (a very high gamma-factor Bussard ramscoop) and the rather clever deflection mechanism that ultimately killed it. It was in "Analog" a couple of years ago. His description of the cone of destruction that the destroyed R-bomb still produced was meticulously worked out and illustrates just how powerful such a device would be. His R-bomb had a gamma-factor of ~1,200 so it was rather extreme and the aggressors only failed because they sent an ultimatum.

Offline Eric Hedman

  • Senior Member
  • *****
  • Posts: 2313
  • The birthplace of the solid body electric guitar
  • Liked: 1953
  • Likes Given: 1142
Re: 99% of Light speed
« Reply #52 on: 09/22/2011 09:02 pm »
An interesting addition to the discussion could be this article in the New York Times:

http://www.nytimes.com/aponline/2011/09/22/world/europe/AP-EU-Breaking-Light-Speed.html?hp


They are reporting from CERN that they have recorded nuetrinos going faster than the speed of light.  Maybe c is not the speed limit everyone thought it was.

Offline Tass

  • Full Member
  • ***
  • Posts: 370
  • Liked: 89
  • Likes Given: 208
Re: 99% of Light speed
« Reply #53 on: 09/23/2011 05:52 am »
An interesting addition to the discussion could be this article in the New York Times:

http://www.nytimes.com/aponline/2011/09/22/world/europe/AP-EU-Breaking-Light-Speed.html?hp


They are reporting from CERN that they have recorded nuetrinos going faster than the speed of light.  Maybe c is not the speed limit everyone thought it was.

Lets not get ahead of the game. The scientists themselves think it is a systematic error. They just publicized it because they need help finding it.

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0