Wow... Our Solar System Is HUGE

[kerbiloid]

Chapter I.
The Rise Of Armada.

Did you see a really horrific and magnificent space fleet?!
No words can actually describe it. That's why this chapter is so brief.

 

Chapter II.
Snowflake.

Snowflake. A tiny snowflake is endlessly drifting along the space, thrown away from its native world by the collision of stars
So long way to fly, so short time compared to the eternity. Brief like this chapter.

 

Epilogue.

Did you see our horrific and magnificent space fleet?!
It should be right here...

Edited July 27, 2020 by kerbiloid

[SOXBLOX]

The Oort cloud is a torus or disc which gradually broadens out into a sphere at its greatest distance. Our models say that the spherical portion is very sparse; it's right on the edge of where the solar gravity has more influence than the galactic tides, so it loses comets frequently. The disc replenishes it over time, but it takes a very long time for these objects to complete even one orbit.

[kerbiloid]

The hypothetical Oort cloud is like the Alcubierre bubble in the @Roverdude's mod.

[Codraroll]

11 hours ago, KSK said:

Edit.  And sometimes it’s better to use a bit of smoke and mirrors in a story anyway. Acknowledge the problem, provide a reasonably plausible (at least on first sight) answer and don’t worry about the details because digging into the details focuses a disproportionate amount of attention on them.

Isn't this (or variations thereof) what he's told in every single of those dozens of threads he creates? Yet the lesson apparently fails to stick...

[KerikBalm]

14 hours ago, Spacescifi said:

Low densiity just means the rocks are spread out... it does not mean some of the rocks are not big like this:

Which makes them easy to detect and avoid. If you spot something 1 AU out, that's 8 light minutes, you've got a 1g acceleration drive, easy peasy.

 

14 hours ago, Spacescifi said:

The outer Oort cloud may have trillions of objects larger than 1 km (0.62 mi), and billions with absolute magnitudes brighter than 11 (corresponding to approximately 20-kilometre (12 mi) diameter), with neighboring objects tens of millions of kilometres apart.

...

It may be closer to a 50/50 chance than it is 99% certainty you will get hit by a massive object.

But we simply do not know.

But we can make good predictions. 

3 hours ago, Spacescifi said:

If google is correct in what I read, the Oort cloud is a SPHERE.

3 hours ago, Spacescifi said:

Flying above the solar disc won't help, as even if you flew above the solar plane you would hit the cloud eventually.

First, we need to define what we are talking about. Sometimes its said that the Oort cloud "is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud."

or

"The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 au (0.03 and 0.08 ly)^[7] to as far as 50,000 au (0.79 ly)^[3] from the Sun. Some estimates place the outer boundary at between 100,000 and 200,000 au (1.58 and 3.16 ly).^[7] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 au (0.32–0.79 ly), and a torus-shaped inner Oort cloud of 2,000–20,000 au (0.0–0.3 ly)."

The torus/ disk shaped region is easily avoided by just avoiding the ecliptic. So its only the spherical outer oort that needs to be considered.

Sometimes they speak of the oort and the hills cloud as separate things. Note, 1 light year = 63,000 AU, and the hills cloud goes out to 1500 AU. Now, with a 1 G drive, you are going to be well below lightspeed when around the hills cloud (assuming you are arriving and decelerating, or leaving and accelerating, not just whizzing by), and that cloud is easy to avoid anyway.

 

Now, the size estimates vary by a lot, but, conservatively, lets assume it is a 2-d shell, at 0.32 ly (larger estimates make it easier, not harder), that is roughly 3e12 km from the sun. Now the area of a sphere is 4*pi*r², so the area of a sphere 3e12km from the sun is roughly 1.1e26 square kilometers.

Now, if we assume there are 1 trillion objects with a 1 km² cross section, they would occupy 1e12 square kilometers. That means a ship passing through would have a probability to hit one of of 8.84e-15. You could pass through 10 trillion times, and the odds are still less tha 1 in 10 that you'd hit them.

Now... the oort cloud doesn't have just large objects, just as the asteroid belt doesn't. In the case of the asteroid belt, roughly half the mass is taken up by 4 asteroids. But lets say we have 10,000x more obejcts in the oort roughly 100mx100m, or 0.1 mk2, then their cros sectional area on this 2d sphere is 100x that of the 1km asteroids.

Probability to hit now goes to 8.84e-13. And then lets say for every 100m class object, you have 10,000 10m class objects, this increases the probability to hit something by another 10x... you've got a change to get hit just going blindly through of 8.84e-11. Ok, lets say 1m objects too, and 10,000x more abundants again: change to hit: 8.84e-9

Ok, 10,000 more 10cm objects, chance to get hit: 8.84e-7. Ok, 1cm objects, 10,000cm more, chance to get hit: 8.84e-5. 1mm objects: chance to get hit: 8.84e-3...

At this point, it looks risky, but the odds are still in your favor. Also in this calculation, I'm assuming the total mass of objects 1/10th the diameter of the next class of objects, have a total mass 10x greater than the larger objects... this isn't the case at all in the asteroid belt, but we don't know the distribution of the Oort clouds mass.

Anyway, this is assuming everything is in a 2-d sphere... make it 3-d, and the chances of a collision drop considerably. So, blind luck should get you through the oort 99% of the time without even hitting something 1mm in size.

However, you need not blindly blunder through the cloud

7 hours ago, Spacescifi said:

Really this thread demonstrates how difficult space travel is... even with impossible tech it is still easy to die.

This thread demonstrates no such thing.

7 hours ago, Spacescifi said:

So it actually encourages making stuff up... not arbitrary... necessary if you want a specific space opera plot.

...

"We were. A space rock hit them along the way. What happens to 9000 ton space battleship when it hits a 500 ton space rock while traveling at 99% lightspeed."

You don't need to make stuff up, if by that you mean FTL and magic tech.

How about you just slow down to 0.9 or 0.8c when going through the Oort, odds are you would be doing that anyway, given how much distance it takes to accelerate to that speed at 1 g even under newtonian physics

3 hours ago, Spacescifi said:

It's the cloud. Absent hyperspace, wormholes or some super warp drive... deal with it. The Oort cloud.

Or don't. Which is what we have done so far.

Scifi either should... or find a way to circumvent it I believe.

Rather than ignore it as if it is not out there.

Its pretty easy to get past. Stick a powerful LIDAR on your ship to spot the objects, you only need to scan a very narrow cone in front of you - evade or deflect objects with a laser.

Lets assume you've got a bussard ramjet, these must ionize the gas infront of them, often with a powerful UV laser, to ionize gas for magnetic collection.

You've just given yourself Active lidar, and a shield against the 1mm and below particles, now you can go through the system with a 0.0001 chance (using the distribution assumes above), without even maneuvering to avoid anything. have a laser to deflect the 1cm particles, and its a 0.000001 chance that you get hit, do some maneuvering for the 10c and above, and you're through no problems. 

Stick on a 10m thick ice shield (what's left cna be used for water at your destination, but I've also seen proposals to use it to breed various useful isotopes by collisions with hydrogen atoms and such - if not using a bussard ramjet that ionizes and collects those)

A baseball may be like an H bomb at .9c (haven't run the numbers, going with the claim), but that drops a lot at 0.8c, and a baseball is fairly big. The oort is likely going to be mostly light volatiles, which won't be very dense.

Now, if you are decelerating in system, your engine exhaust should deflect small objects, and if its a 1 g constant thrust drive, its going to be something like a photon rocket, or its exaust will be relativistic particles, which will make a great "illumination source" for detecting larger objects.

 

So in summary:

• You won't be going .99c through the oort with your tech/acceleration anyway
• avoid the ecliptic and avoid most of the problem, and its just the spherical outer oort - trivially easy with your tech level
• Blindly going through the oort with no precautions will work more than 99 out of 100 times
• Installing focused forward looking lidar will allow you to spot any threatening objects - trivially easy with your tech level
• Small particles can be absorbed with a shield or deflected, deflection will happen anyway if using bussard ramjet tech

It seems to me that you're just trying to make an excuse to say: "Oh well, there's no choice but yet another contrived form of FTL"

 

 

 

 

 

 

[KSK]

7 hours ago, Spacescifi said:

So it actually encourages making stuff up... not arbitrary... necessary if you want a specific space opera plot.

What IS NOT NECESSARY: Artificial field gravity. Other realistic easier ways to do it, and while 1g constant acceleration is currently a dream, it is at least a concept readers can understand as opposed to a totally arbritary 1g field we make up with arbritray limits imposed. 

Plasma weapons: We know in previous thread why.

Basically, where necessary make stuff up, where reality does a good job... KEEP IT.

How are you deciding what is realistic though? Genuine question, not intended to be a snark.

For me 'realistic' implies that it has to have at least some grounding in what we understand now and are technologically capable of now. But what we're capable of now isn't necessarily what's possible in a science fiction setting and  a technology that's not realistic now might be entirely realistic in that setting.  So 'where necessary make stuff up, where reality does a good job... KEEP IT' becomes 'where necessary make stuff up, where reality - as we understand it NOW - does a good job... KEEP IT.'

That's not necessarily a problem in a sci-fi setting. Maybe there are good reasons in that setting for holding on to old technologies. Maybe the old adage of 'if it ain't broke don't fix it' is relevant. Maybe the new technology is only just being developed - great for cutting edge experimental applications but not so good if you want a solid, reliable system that you know is going to work.  But handled badly, you can end up with an anachronism stew of concepts from different eras and different technology levels that don't really make much sense together. The further apart those eras are, the worse it can get.

To use a slightly facetious example, we wouldn't normally use stone or bone tools in the 21st century. I mean sure, they would work for some applications, they're certainly a tried-and-true technology that served our distant ancestors well, but on the whole we have better options available these days.  

Artificial gravity fields are another, more sci-fi example. They're not strictly necessary but they're certainly useful and, depending on the technology available within your sci-fi setting, might be the natural way to solve certain problems, or be so routine that that there's no good reason not to use them.

For example, if you're writing in a setting where Alcubierre style warp drive is possible. You have a drive that's capable of expanding space on one side of a spaceship and contracting it on the other. In other words you have the technology to change the curvature of space to suit your needs, that is, to create artificial gravity fields - or antigravity fields for that matter.  Which are potentially useful for all sorts of things, from not having to worry about zero-g conditions onboard starships, to creating tractor beams (which themselves could be enormously useful for large scale construction projects), to antigravity drives, to shields capable deflecting space rocks, or even laser beams. Of course, you the author might choose to impose some limits that rule out one or more of those applications but that's another conversation altogether.

The point is that you now have a bunch of completely sci-fi technologies that are not realistic now but might be entirely realistic in a setting where warp drive is a reality. Even better, (to my mind) all those technologies depend on the same underlying principles to work, so putting them together gives that setting a nice consistent feel.

 

 

 

 

[Spacescifi]

1 hour ago, KerikBalm said:

Which makes them easy to detect and avoid. If you spot something 1 AU out, that's 8 light minutes, you've got a 1g acceleration drive, easy peasy.

 

But we can make good predictions. 

First, we need to define what we are talking about. Sometimes its said that the Oort cloud "is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud."

or

"The Oort cloud is thought to occupy a vast space from somewhere between 2,000 and 5,000 au (0.03 and 0.08 ly)^[7] to as far as 50,000 au (0.79 ly)^[3] from the Sun. Some estimates place the outer boundary at between 100,000 and 200,000 au (1.58 and 3.16 ly).^[7] The region can be subdivided into a spherical outer Oort cloud of 20,000–50,000 au (0.32–0.79 ly), and a torus-shaped inner Oort cloud of 2,000–20,000 au (0.0–0.3 ly)."

The torus/ disk shaped region is easily avoided by just avoiding the ecliptic. So its only the spherical outer oort that needs to be considered.

Sometimes they speak of the oort and the hills cloud as separate things. Note, 1 light year = 63,000 AU, and the hills cloud goes out to 1500 AU. Now, with a 1 G drive, you are going to be well below lightspeed when around the hills cloud (assuming you are arriving and decelerating, or leaving and accelerating, not just whizzing by), and that cloud is easy to avoid anyway.

 

Now, the size estimates vary by a lot, but, conservatively, lets assume it is a 2-d shell, at 0.32 ly (larger estimates make it easier, not harder), that is roughly 3e12 km from the sun. Now the area of a sphere is 4*pi*r², so the area of a sphere 3e12km from the sun is roughly 1.1e26 square kilometers.

Now, if we assume there are 1 trillion objects with a 1 km² cross section, they would occupy 1e12 square kilometers. That means a ship passing through would have a probability to hit one of of 8.84e-15. You could pass through 10 trillion times, and the odds are still less tha 1 in 10 that you'd hit them.

Now... the oort cloud doesn't have just large objects, just as the asteroid belt doesn't. In the case of the asteroid belt, roughly half the mass is taken up by 4 asteroids. But lets say we have 10,000x more obejcts in the oort roughly 100mx100m, or 0.1 mk2, then their cros sectional area on this 2d sphere is 100x that of the 1km asteroids.

Probability to hit now goes to 8.84e-13. And then lets say for every 100m class object, you have 10,000 10m class objects, this increases the probability to hit something by another 10x... you've got a change to get hit just going blindly through of 8.84e-11. Ok, lets say 1m objects too, and 10,000x more abundants again: change to hit: 8.84e-9

Ok, 10,000 more 10cm objects, chance to get hit: 8.84e-7. Ok, 1cm objects, 10,000cm more, chance to get hit: 8.84e-5. 1mm objects: chance to get hit: 8.84e-3...

At this point, it looks risky, but the odds are still in your favor. Also in this calculation, I'm assuming the total mass of objects 1/10th the diameter of the next class of objects, have a total mass 10x greater than the larger objects... this isn't the case at all in the asteroid belt, but we don't know the distribution of the Oort clouds mass.

Anyway, this is assuming everything is in a 2-d sphere... make it 3-d, and the chances of a collision drop considerably. So, blind luck should get you through the oort 99% of the time without even hitting something 1mm in size.

However, you need not blindly blunder through the cloud

This thread demonstrates no such thing.

You don't need to make stuff up, if by that you mean FTL and magic tech.

How about you just slow down to 0.9 or 0.8c when going through the Oort, odds are you would be doing that anyway, given how much distance it takes to accelerate to that speed at 1 g even under newtonian physics

Its pretty easy to get past. Stick a powerful LIDAR on your ship to spot the objects, you only need to scan a very narrow cone in front of you - evade or deflect objects with a laser.

Lets assume you've got a bussard ramjet, these must ionize the gas infront of them, often with a powerful UV laser, to ionize gas for magnetic collection.

You've just given yourself Active lidar, and a shield against the 1mm and below particles, now you can go through the system with a 0.0001 chance (using the distribution assumes above), without even maneuvering to avoid anything. have a laser to deflect the 1cm particles, and its a 0.000001 chance that you get hit, do some maneuvering for the 10c and above, and you're through no problems. 

Stick on a 10m thick ice shield (what's left cna be used for water at your destination, but I've also seen proposals to use it to breed various useful isotopes by collisions with hydrogen atoms and such - if not using a bussard ramjet that ionizes and collects those)

A baseball may be like an H bomb at .9c (haven't run the numbers, going with the claim), but that drops a lot at 0.8c, and a baseball is fairly big. The oort is likely going to be mostly light volatiles, which won't be very dense.

Now, if you are decelerating in system, your engine exhaust should deflect small objects, and if its a 1 g constant thrust drive, its going to be something like a photon rocket, or its exaust will be relativistic particles, which will make a great "illumination source" for detecting larger objects.

 

So in summary:

• You won't be going .99c through the oort with your tech/acceleration anyway
• avoid the ecliptic and avoid most of the problem, and its just the spherical outer oort - trivially easy with your tech level
• Blindly going through the oort with no precautions will work more than 99 out of 100 times
• Installing focused forward looking lidar will allow you to spot any threatening objects - trivially easy with your tech level
• Small particles can be absorbed with a shield or deflected, deflection will happen anyway if using bussard ramjet tech

It seems to me that you're just trying to make an excuse to say: "Oh well, there's no choice but yet another contrived form of FTL"

 

 

 

 

 

 

 

Congratulations! You have a fighting chance of surviving the Oort cloud!

Where there is will... there is a REALLY hard way at times.

I hardly need excuses, if I can't find a way out of a paper bag I find someone who can. If they tell me I will have do a bunch of things that will take more time than I want to take... then making it up is preferable.

Time dilation leads to a very specific kind of story I cannot afford for the plot to work at all.

Imagine Star Wars with time dilation... or Star Trek.

Neither would be the same. Not that I am doing that.

53 minutes ago, KSK said:

How are you deciding what is realistic though? Genuine question, not intended to be a snark.

For me 'realistic' implies that it has to have at least some grounding in what we understand now and are technologically capable of now. But what we're capable of now isn't necessarily what's possible in a science fiction setting and  a technology that's not realistic now might be entirely realistic in that setting.  So 'where necessary make stuff up, where reality does a good job... KEEP IT' becomes 'where necessary make stuff up, where reality - as we understand it NOW - does a good job... KEEP IT.'

That's not necessarily a problem in a sci-fi setting. Maybe there are good reasons in that setting for holding on to old technologies. Maybe the old adage of 'if it ain't broke don't fix it' is relevant. Maybe the new technology is only just being developed - great for cutting edge experimental applications but not so good if you want a solid, reliable system that you know is going to work.  But handled badly, you can end up with an anachronism stew of concepts from different eras and different technology levels that don't really make much sense together. The further apart those eras are, the worse it can get.

To use a slightly facetious example, we wouldn't normally use stone or bone tools in the 21st century. I mean sure, they would work for some applications, they're certainly a tried-and-true technology that served our distant ancestors well, but on the whole we have better options available these days.  

Artificial gravity fields are another, more sci-fi example. They're not strictly necessary but they're certainly useful and, depending on the technology available within your sci-fi setting, might be the natural way to solve certain problems, or be so routine that that there's no good reason not to use them.

For example, if you're writing in a setting where Alcubierre style warp drive is possible. You have a drive that's capable of expanding space on one side of a spaceship and contracting it on the other. In other words you have the technology to change the curvature of space to suit your needs, that is, to create artificial gravity fields - or antigravity fields for that matter.  Which are potentially useful for all sorts of things, from not having to worry about zero-g conditions onboard starships, to creating tractor beams (which themselves could be enormously useful for large scale construction projects), to antigravity drives, to shields capable deflecting space rocks, or even laser beams. Of course, you the author might choose to impose some limits that rule out one or more of those applications but that's another conversation altogether.

The point is that you now have a bunch of completely sci-fi technologies that are not realistic now but might be entirely realistic in a setting where warp drive is a reality. Even better, (to my mind) all those technologies depend on the same underlying principles to work, so putting them together gives that setting a nice consistent feel.

 

 

 

 

 

I understand... but part of the appeal is the thrtll of space travel. 

It's expensive IRL, but I can surely let the reader experience what it's like to float in weightlessness.

That's my primary reason against AG fields.

Adventures through writing.

What if questions.

Ironically when creating aliens physics gives a lot more freedom and leeway than making their spaceships.

So honestly, I have to make up more with the spaceships than the aliens themselves LOL.

Edited July 27, 2020 by Spacescifi

[Hannu2]

On 7/26/2020 at 9:17 AM, Spacescifi said:

The oort cloud is a region where the sun's gravity is more or less null and void.

The oort cloud is about 2 LY accross if I read correctly.

It would take the Voyager probe 300 years of inertia driftng just to reach the edge of the oort cloud, but by then it's instruments will be long dead anyway.

It is the edge of the solar system if you consider where the sun's influence ends.

 

I do not like common hype about probes "leaving solar system" when they just pass the heliopause. It is very artificial definition of edge of solar system, because there are billions of objects gravitationally bound to Sun at larger distances.

On 7/26/2020 at 9:17 AM, Spacescifi said:

It is rather hard to dodge rocks in your path at that speed, and we are talking TWO light years worth of rocks scattered about. Any one of which could ruin your lovely trip.

Like you either need an UBER deflector shield to protect a vessel from asteroids or need to go in guns blazing with several antimatter particle beams to blast the rocks before they reach you.

As per the usual... offense is easier to do than defense... it would take a truly scifi deflector field to deflect rocks when you're going at 99% lightspeed.

Or you assume that space travelers are brave and can handle a risk of millionths or billionths to hit the rock. Probability to hit something is probable less than in single street crossing in average city.

[kerbiloid]

Does the relativistic growth of mass affect the gravity?
(I have read both yes&no versions, so have no clear opinion on this.)

I.e should an ultrarelativistic ship breaking in the (hypothetical) Oort cloud attract troubles like in the Universe Sandbox?

Edited July 27, 2020 by kerbiloid

[Hannu2]

18 minutes ago, kerbiloid said:

Does the relativistic growth of mass affect the gravity?
(I have read both yes&no versions, so have no clear opinion on this.)

I.e should an ultrarelativistic ship breaking in the (hypothetical) Oort cloud attract troubles like in the Universe Sandbox?

Geometry of spacetime (i.e. gravity) is affected by stress-energy tensor. It takes momentum (i.e. speed of massive object) into account, but as far as I know, you can not replace mass with just simple mass growth effect but you have to make nasty tensor calculations. In any case reasonable interstellar ships can not cause dramatic effects for bodies around if they do not collide. Getting enough energy to accelerate someting to so extreme velocities than it can disturb nearby celestial objects cause probably more problematic effects to space around and objects there.

https://en.wikipedia.org/wiki/Stress–energy_tensor

[KSK]

1 hour ago, Spacescifi said:

I understand... but part of the appeal is the thrtll of space travel. 

It's expensive IRL, but I can surely let the reader experience what it's like to float in weightlessness.

That's my primary reason against AG fields.

Adventures through writing.

What if questions.

Of course - I can totally understand that. 

Heck, it’s not dissimilar to one of my character’s attitude in one of my short stories, in which he was strongly motivated by getting out there on EVA and exploring space in person rather than sitting in a nice cosy spacecraft and experiencing everything through augmented reality.

But that wasn’t the point you were making in your previous post in which you objected to artificial field gravity as unnecessary or arbitrary when there were more realistic alternatives.

[KerikBalm]

3 hours ago, Spacescifi said:

Congratulations! You have a fighting chance of surviving the Oort cloud!

Where there is will... there is a REALLY hard way at times.

Really hard way? Its trivial once you have your awesome propulsion system. If its a photon rocket, the energy needed to operate a LIDAR and dodge the bigger pieces is trivial.

If its a Bussard ramjet, the design basically has a built in forward looking LIDAR with "energy deflector shields" (well ionizing laser and magnets, this is still hard-sci fi tech) that will work against the small particles, so you just avoid the larger ones. A bussard ramjet would be one of the ways you might get your constant thrust drive anyway.

So solve the propulsion problem, and your "really hard way" becomes : steer a little bit to avoid little objects that you might hit once in every 10,000 trips

And keep in mind, I was using a pretty generous size distribution to estimate a lot of small particles, with the mass of particles/objects under 1 km completely dwarfing the mass of those over 1km, with the mass of particles around 1mm in size being 1 million times more massive than the mass of objects 1km or greater. (1 cm class objects being 100,000x more massive, and 1/10th the mass of the 1mm class objects).

This is so far from the case with the asteroids, where 4 asteroids are more massive than everything else combined. So, I'm being really really really generous here.

Its not a problem.

[SOXBLOX]

We will assume that the Oort Cloud extends from 2000 to 200 000 A.U. Next, that it is populated by 3 trillion objects capable of wrecking your ship, evenly distributed in the Cloud. Next, your ship is a cylinder with a radius of 15 m, and flies in a straight line. 

Running the numbers, I found that there are ~0.000 000 000 000 000 536 objects in your path. The chances of a collision are miniscule.

4 hours ago, Hannu2 said:

Geometry of spacetime (i.e. gravity) is affected by stress-energy tensor. It takes momentum (i.e. speed of massive object) into account, but as far as I know, you can not replace mass with just simple mass growth effect but you have to make nasty tensor calculations. In any case reasonable interstellar ships can not cause dramatic effects for bodies around if they do not collide. Getting enough energy to accelerate someting to so extreme velocities than it can disturb nearby celestial objects cause probably more problematic effects to space around and objects there.

https://en.wikipedia.org/wiki/Stress–energy_tensor

You can just calculate the gamma factor for a instantaneous speed relative to an inertial observer. Much easier.

[Spacescifi]

2 hours ago, KerikBalm said:

Really hard way? Its trivial once you have your awesome propulsion system. If its a photon rocket, the energy needed to operate a LIDAR and dodge the bigger pieces is trivial.

If its a Bussard ramjet, the design basically has a built in forward looking LIDAR with "energy deflector shields" (well ionizing laser and magnets, this is still hard-sci fi tech) that will work against the small particles, so you just avoid the larger ones. A bussard ramjet would be one of the ways you might get your constant thrust drive anyway.

So solve the propulsion problem, and your "really hard way" becomes : steer a little bit to avoid little objects that you might hit once in every 10,000 trips

And keep in mind, I was using a pretty generous size distribution to estimate a lot of small particles, with the mass of particles/objects under 1 km completely dwarfing the mass of those over 1km, with the mass of particles around 1mm in size being 1 million times more massive than the mass of objects 1km or greater. (1 cm class objects being 100,000x more massive, and 1/10th the mass of the 1mm class objects).

This is so far from the case with the asteroids, where 4 asteroids are more massive than everything else combined. So, I'm being really really really generous here.

Its not a problem.

 

Hmmm... hard scifi?

Photon rockets of 1g requires radiator fins several kilometers or much greater in length and width.

How are going to shield those?

When all factors are taken into account,  hard scifi falls apart at tasks that more or less require making stuff up.

[KerikBalm]

1 hour ago, Spacescifi said:

Hmmm... hard scifi?

Photon rockets of 1g requires radiator fins several kilometers or much greater in length and width.

How are going to shield those?

When all factors are taken into account,  hard scifi falls apart at tasks that more or less require making stuff up.

Well, we just talked about shielding... You don't really need it because of how unlikely it is.

Also, the radiator can be long and thin, behind a relatively small shield, all incoming particles will be coming nearly parallel.

Besides, you mentioned the 1g drive.... I'd go with some kind of fusion rocket getting 0.1g or less, or a bussard scramjet 

[Spacescifi]

27 minutes ago, KerikBalm said:

Well, we just talked about shielding... You don't really need it because of how unlikely it is.

Also, the radiator can be long and thin, behind a relatively small shield, all incoming particles will be coming nearly parallel.

Besides, you mentioned the 1g drive.... I'd go with some kind of fusion rocket getting 0.1g or less, or a bussard scramjet 

 

Behind the ship?

Where the photon rays are shooting?

That will burn up the radiator fins.

The math does not look good if you calculate the radiator fin size for a 1g photon rocket. It's extreme.

Nevermind the weight, which would be massive.

Which means the RCS will use large amounts of propellant unless you want to take days rotating the vessel.

And photon rockets require working mass to get their power... antimatter.

And the slower option?

Have a nice voyage. You're leaving home as you know it forever.

Wayyy too slow.

Edited July 27, 2020 by Spacescifi

[SOXBLOX]

And you want a photonic rocket why?

[Spacescifi]

Just now, SOXBLOX said:

And you want a photonic rocket why?

 

I never mentioned one.

I mentioned a scifi constant 1g drive with no propellant.

I added no details.

I know it's fiction... and I also know it is NOT a photon drive which has great challenges.

[SOXBLOX]

8 minutes ago, Spacescifi said:

photon rocket

Ahem.

[KerikBalm]

28 minutes ago, Spacescifi said:

Behind the ship?

Where the photon rays are shooting?

That will burn up the radiator fins.

Not behind the engine exhaust, obviously.

Shield<radiator<reactor<exhaust

Quote

The math does not look good if you calculate the radiator fin size for a 1g photon rocket. It's extreme.

Yes, but you want a 1g thruster, you need a high isp. The radiator mass is directly linked to how efficient the drive is. I can accept 99 oo% efficiency before FTL.

Quote

Which means the RCS will use large amounts of propellant unless you want to take days rotating the vessel.

Thrust vectoring, and days to rotate is fine for a voyage lasting years 

Quote

And the slower option?

Have a nice voyage. You're leaving home as you know it forever.

Wayyy too slow.

A bussard scramjet could be very fast, and have very low radiator requirements.

Its a bit wooly, but if you want fast interstellar travel with the hardest science you can, bussard scramjets are what you want if 5%c fusion rocket is not enough

Edited July 27, 2020 by KerikBalm

[Spacescifi]

8 hours ago, KerikBalm said:

Not behind the engine exhaust, obviously.

Shield<radiator<reactor<exhaust

Yes, but you want a 1g thruster, you need a high isp. The radiator mass is directly linked to how efficient the drive is. I can accept 99 oo% efficiency before FTL.

Thrust vectoring, and days to rotate is fine for a voyage lasting years 

A bussard scramjet could be very fast, and have very low radiator requirements.

Its a bit wooly, but if you want fast interstellar travel with the hardest science you can, bussard scramjets are what you want if 5%c fusion rocket is not enough

 

Even 1% waste heat requires VAST radiators with 1g photon rockets. That is about the most energy inefficient drive known theoretically. We are talking perphaps 100 kilometer or longer radiator fins, lwhich cannot be afford to get hit because then you cannot do 1g anymore.

The bussard ram jet last I read does not have enough hydrogen in interstellar space to make it practical. Near a star it could work great.

Either way... 'fast IRL' is too slow sometimes for what a writer needs.

Moden tech and feasible plans is barely human rated for travel within our own system.

Trying to reach the next with only it is pushing the achievment bar rather high I think.

Edited July 28, 2020 by Spacescifi

[StrandedonEarth]

2 hours ago, Spacescifi said:

energy inefficient drive

Inefficient, yes, but also propellant-less

[Spacescifi]

15 minutes ago, StrandedonEarth said:

Inefficient, yes, but also propellant-less

Going through several bus load tons of antimatter is not exactly propellantless... but I digress.

That is the kind of power needed.

Roughly. Actual calculations may be farther or closer to this, but it's in that ball park.

Basically more than enough to energy to create a nuclear winter on Earth, or make brand new craters miles across that dwarf anything seen.

For that matter, that is enough energy to glass some smaller countries entirely... literalky burning them to ash with a push of a button.

Edited July 28, 2020 by Spacescifi

[SOXBLOX]

Ok, then. You can ignore the numbers if you want. As long as you don't hit Star Wars levels of nonsense, I'm happy. 

So, how do you plan to solve your contrived problem of massive, unshielded radiators for your ludicrously OP flashlight rocket? (In the UK, this translates to "torch drive". Heh.)

Edited July 28, 2020 by SOXBLOX

[Spacescifi]

22 minutes ago, SOXBLOX said:

Ok, then. You can ignore the numbers if you want. As long as you don't hit Star Wars levels of nonsense, I'm happy. 

So, how do you plan to solve your contrived problem of massive, unshielded radiators?

 

It's not contrived. It's real IF you stick with known science.

In scifi you can ignore that like most popular media SF do... big shiny spaceship without massive rad fins that can FTL warp accross the galaxy.

Where does the waste heat go?

Who knows?

Maybe an alternate dimension, since portaling it to other worlds would nuke everything on the other end of the portal gate.

Make stuff up.

It's necessary at times in scifi.

And I never said I was using a photon drive in my Scifi.

I rather make up stuff that is more user friendly.

 

Edited July 28, 2020 by Spacescifi