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How not to get lost with FTL jumps?


Spacescifi

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One last post... for real this time.

How?

Here are two ideas for jump drives, one will take you far and probably get you lost. The other will take you a lot longer to get far but you at least can track better.

 

Jump drive one: No FTL sensors at all. You jump navigate by jumping to any light source you see, only deciding how far or how close you want to arrive. You will arrive however close to where the light source WAS. Because of light lag.

To power up for each jump takes an hour. Computer maps with nsvigation help but still...

The problem is you can use this to jump really far. Like another galaxy. And if you jump that far, the stars won't look the same anymore. Your point of refence will be harder. The good thing is that with smaller jumps it is easier yo grasp your point of reference. The closer you get equals less light lag for more accurate jumps.

 

Jump drive 2: Comes in 3 flavors. 5 LY max on a single jump, 15 max on a single jump, and 30 max on a single jump.

 

There is a catch, or three to be precise.

1. Jump range requires a jump powering up time and a time for dumping jump particles. In other words, a 5 LY drive takes 5 min to power up to jump, and another 5 min after jumping to emit jump particles.

2. Jump particles can only be detected by jump sensors, which most jump ships have. Jump particles can be detected by jump sensors 50 LY out. Jump particles tell a a ship's exact location and speed.

3. Other than jump sensors, no FTL sensors exist.

 

So, how do you avoid getting lost with jump drive one? Personally I think jump drive two is just better, since the jump sensors can be used for lead ship following navigation. Jump drive one lacks ANY jump sensors.

 

Bonus question: if you had to choose one or the other for scifi humans which would you pick? Knowing scifi aliens, both tolerable and intiolerable get the other jump drive?

Edited by Spacescifi
Because of light lag hour jump power ul
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I do not see a problem with Jump drive 1.

Generally speaking, we know how fast and in which direction a given star is moving, so there is no problem with making a jump to within a light-year of your estimated destination(less of you are traveling less than hundreds of LY for the first jump), then check where you expect it to be, and make your second jump to inside the system, at which point you are within light-hours of your destination(Pluto's orbit is all of 10 light hours across), and you can be pretty confident that things are roughly where you see them.

If you(or another ship you have communicated with) has been to the system in the last year, you can even skip the first extra-system jump and just jump straight into the system.

Star-systems do not tend to turn very quickly, so all you really need for navigation(in addition to your own location, which you presumably have before your first jump) is a 'last known time-space location' and a movement vector, and your computer can easily determine the position of the star and any planets of interest around it.

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But, but... You promised!

OT, the limits of the second one seem entirely arbitrary. I don't like that.

For the first one, there is nothing intrinsic in light that can tell you anything about the distance of the source. Our distance measurements to stars rely on various methods like parallax, redshift, standard candles, etc but all require a good deal of interpretation. The light itself doesn't have a "return to" address tag.

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16 minutes ago, Shpaget said:

But, but... You promised!

OT, the limits of the second one seem entirely arbitrary. I don't like that.

For the first one, there is nothing intrinsic in light that can tell you anything about the distance of the source. Our distance measurements to stars rely on various methods like parallax, redshift, standard candles, etc but all require a good deal of interpretation. The light itself doesn't have a "return to" address tag.

 

Scifi is by nature arbitrary unless it is based on what we know how to do. Also the constraints of whatever the writer is trying to make happen.

 

And I know light doe not have a return adrress tag, but I made the first jump drive ro jump to near where the light source was to make navigation more of a challenge.

If it jumped near where the light source was in real time that would require FTL sensors or good guessing.

17 minutes ago, Terwin said:

I do not see a problem with Jump drive 1.

Generally speaking, we know how fast and in which direction a given star is moving, so there is no problem with making a jump to within a light-year of your estimated destination(less of you are traveling less than hundreds of LY for the first jump), then check where you expect it to be, and make your second jump to inside the system, at which point you are within light-hours of your destination(Pluto's orbit is all of 10 light hours across), and you can be pretty confident that things are roughly where you see them.

If you(or another ship you have communicated with) has been to the system in the last year, you can even skip the first extra-system jump and just jump straight into the system.

Star-systems do not tend to turn very quickly, so all you really need for navigation(in addition to your own location, which you presumably have before your first jump) is a 'last known time-space location' and a movement vector, and your computer can easily determine the position of the star and any planets of interest around it.

Good job. An aneutronic fusion rocket would be ideal here, but I stiil do not think it is the safest choice to land with.

Once you have to refuel your propellant, and you mine a moon or a gas giant, as well as stuff to make fusion happen, there is a dstinct possibity that your scooped fuel won't be safe.

Helium 3, while plentiful on the moon and useful for fusion I have read that the byproducts in the exhaust are not aneutronic.

You need boron for that I read.

So unless you are picky about fuel sources, landing on planets could irradiate the landing zone.

Grav-inverters for falling upward while fiction allows one to use rockets in space and not be picky about fuel sources.

Since space is full of radiation anyway.

Edited by Spacescifi
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15 minutes ago, Spacescifi said:

Good job. An aneutronic fusion rocket would be ideal here, but I stiil do not think it is the safest choice to land with.

Once you have to refuel your propellant, and you mine a moon or a gas giant, as well as stuff to make fusion happen, there is a dstinct possibity that your scooped fuel won't be safe.

Helium 3, while plentiful on the moon and useful for fusion I have read that the byproducts in the exhaust are not aneutronic.

You need boron for that I read.

So unless you are picky about fuel sources, landing on planets could irradiate the landing zone.

Grav-inverters for falling upward while fiction allows one to use rockets in space and not be picky about fuel sources.

Since space is full of radiation anyway.

If you are mining fuel from a natural body, you will need to refine it and remove any hazardous/toxic materials anyway, so even if you land directly on your only available fuel-source, you would probably only need to scrape off the surface material.  After all, space is full or radiation, and your engine is hardly the most prolific source.

(Spraying your tritium(h3) fuel source with extra neutrons is probably not a bad idea any way, as that can help convert deuterium(h2) into tritium(h3) and thus enrich your fuel.)

Of course a stray neutron has a half-life of only about 10 minutes, so any of them that do not get bound up into an atom are probably not going to stick around very long anyway.

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30 minutes ago, Terwin said:

If you are mining fuel from a natural body, you will need to refine it and remove any hazardous/toxic materials anyway, so even if you land directly on your only available fuel-source, you would probably only need to scrape off the surface material.  After all, space is full or radiation, and your engine is hardly the most prolific source.

(Spraying your tritium(h3) fuel source with extra neutrons is probably not a bad idea any way, as that can help convert deuterium(h2) into tritium(h3) and thus enrich your fuel.)

Of course a stray neutron has a half-life of only about 10 minutes, so any of them that do not get bound up into an atom are probably not going to stick around very long anyway.

 

I can see it now. The alien version of door dash food delivery, but with starship shuttles with fusion drives!

Say you ordered an alien pizza (tastes really good) for delivery and the shuttle lands in the street in front of YOUR HOUSE. Alien guy jumps out in a protected space suit, rings door bell, you take your puzza and he launches off again. Granted he is using the air for propellant to save on fuel but still, it is fusion.

 

Just curious, are you still not worried about the stray neutron half-life?

 

Really I just enjoy taking popular scifi out to the shed and whipping it. Metaphorically speaking. Taking it to task for it's favored mode of transport 

Both star trek and probably even Star Wars presume that you can just fly around with a fusion drive anywhere and it's okay. Nobody gets cancer!

 

Aneutronic fusion would be the best engine choice for the shuttle, which can have 1% of leaky neutrons.

Edited by Spacescifi
Cancer
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47 minutes ago, Spacescifi said:

 

I can see it now. The alien version of door dash food delivery, but with starship shuttles with fusion drives!

Say you ordered an alien pizza (tastes really good) for delivery and the shuttle lands in the street in front of YOUR HOUSE. Alien guy jumps out in a protected space suit, rings door bell, you take your puzza and he launches off again. Granted he is using the air for propellant to save on fuel but still, it is fusion.

 

Just curious, are you still not worried about the stray neutron half-life?

 

Really I just enjoy taking popular scifi out to the shed and whipping it. Metaphorically speaking. Taking it to task for it's favored mode of transport 

Both star trek and probably even Star Wars presume that you can just fly around with a fusion drive anywhere and it's okay. Nobody gets cancer!

I would be more immediately concerned about the street in front of my house and the front half of my car both being semi-molten and no longer usable.

Also, the front of my house (assuming it was not knocked over) has also been seriously eroded and is probably on fire.  Plus the sheer volume of the noise caused by a rocket engine has rendered me deaf, and possibly dead(rocket engineers need to be careful to *not* knock over near-by buildings with sound alone, usually with active sound damping, such as all that water they spray at the base of the rockets they launch at KSC).

 

Stray neutrons are *not* your major concern if you have a rocket launching or landing within half a mile of your house, and if it is not within half a mile, then you probably do not care about the stray neutrons anyway.

 

Edit:

The sound damping system at KSC uses 300,000 gallons of water, for a mass of ~3 million pounds; compared to 4.3 million pounds for the entire shuttle stack at lift-off.

This is *not* something your delivery driver could carry with them.

Edited by Terwin
sound dampening mass comparison added
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16 minutes ago, Terwin said:

I would be more immediately concerned about the street in front of my house and the front half of my car both being semi-molten and no longer usable.

Also, the front of my house (assuming it was not knocked over) has also been seriously eroded and is probably on fire.  Plus the sheer volume of the noise caused by a rocket engine has rendered me deaf, and possibly dead(rocket engineers need to be careful to *not* knock over near-by buildings with sound alone, usually with active sound damping, such as all that water they spray at the base of the rockets they launch at KSC).

 

Stray neutrons are *not* your major concern if you have a rocket launching or landing within half a mile of your house, and if it is not within half a mile, then you probably do not care about the stray neutrons anyway.

 

Edit:

The sound damping system at KSC uses 300,000 gallons of water, for a mass of ~3 million pounds; compared to 4.3 million pounds for the entire shuttle stack at lift-off.

This is *not* something your delivery driver could carry with them.

 

LOL.

 

So valerian's daring escape would likely leave him with second degree burns and hearing loss? Assuming his ship uses fusion?

Wow. I really want to see a scifi movie with physics turned on LOL

 

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1 hour ago, Spacescifi said:

Wow. I really want to see a scifi movie with physics turned on LOL

 

It's not a movie, but if you ignore the arbitrarally high ISP of the drives, The Expanse isnt that bad. Earth tech in Babylon 5 also generally follows earth physics.

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13 minutes ago, Rakaydos said:

It's not a movie, but if you ignore the arbitrarally high ISP of the drives, The Expanse isnt that bad. Earth tech in Babylon 5 also generally follows earth physics.

 

I doubt it shows the raw power of landing a large fusion rocket vessel on a planet.

People who make pop scifi seem like they confuse the overpowering shockwaves of rocket exhaust with the mere loud hum of a jet engine.

There is a difference.

I wanna see something like the craziest scott manley has done with unlimited fuel mods. But in a movie via a realustic fusion drive.

Edited by Spacescifi
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6 hours ago, Spacescifi said:

So valerian's daring escape would likely leave him with second degree burns and hearing loss? Assuming his ship uses fusion?

Wow. I really want to see a scifi movie with physics turned on LOL

Possibly, but those look a lot more like jet engines than rocket engines.  Also, there is no indication that they are getting anywhere near orbital velocities as opposed to just climbing high in the sky to avoid bringing planetary chunks along for the ride.

I have not seen that movie, so I can't speak for how a large flying vehicle like that one could travel at off-road bus speeds and stay in the air with little or no wing surface, but I am sure they are using the same space-magic to protect the gang-plank.

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@Spacescifi, you can ditch the FTL sensors entirely. Pulsars are considered sufficiently reliable for navigation purposes as a galaxy-wide GPS with accuracy of ±5 km; there is an experimental implementation that has showed 7 km accuracy after two days of observations.

 

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Spoiler
1 hour ago, DDE said:

Pulsars are considered sufficiently reliable for navigation purposes as a galaxy-wide GPS with accuracy of ±5 km

GALANASS navigation system rulez.

"Use pulsars to herd your cow!"

 

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14 hours ago, Shpaget said:

there is nothing intrinsic in light that can tell you anything about the distance of the source. ... The light itself doesn't have a "return to" address tag.

Exactly

14 hours ago, Spacescifi said:

Scifi is by nature arbitrary unless it is based on what we know how to do. Also the constraints of whatever the writer is trying to make happen.

I'd have to strongly disagree with this. "Scifi" that is full of arbitrary stuff is nothing more than fantasy set in a futuristic setting rather than a pseudo-medieval setting.

Proper Scientific fiction is fiction based on our current scientific understanding of the universe. Some handwaving and arbitrary properties of tech are fine as long as they obey the laws of physics as we know them.

What I mean by acceptable levels of arbitrary-ness is like: the smallest fusion reactions are 10 tons, and only produces 5 megawatts of surplus power, but larger reactors on the scale of 100 tons produce 500 megawatts of fusion power. Fusion reactor efficiency increasing with size is something we already observe, but my power to weight ratios are pulled out of thin air.

Maybe such high fusion reaction rates violate some law of physics, but so far there is nothing obvious there, and nothing that allows time travel, infinite energy, or easy access to unstoppable planet killing weapons (unstoppable planet killing weapons would still be possible, but still very resource intensive to make)...

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6 hours ago, DDE said:

@Spacescifi, you can ditch the FTL sensors entirely. Pulsars are considered sufficiently reliable for navigation purposes as a galaxy-wide GPS with accuracy of ±5 km; there is an experimental implementation that has showed 7 km accuracy after two days of observations.

I considered pulsars for determining where you currently are, but:

20 hours ago, Spacescifi said:

The problem is you can use this to jump really far. Like another galaxy.

Also, the question seemed more about how to get where you are going, so for pulsars to be useful for that purpose, you would also need a map of wherever you were going.

Calculating current relative position and speed/direction of travel on the other hand are things we have been doing for quite some time and can be done(inefficiently) without any sort of prior setup.

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Spoiler

The Multiverse even can't see a problem.

First you jump to the required galaxy and do what you want.

Then you jump to an alternative universe galaxy looking enough similar to yours.

After a little training you even don't need to jump here and there, the samples from another galaxy just appear at your table.

 

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Presumably we would have to be very advanced to be able to employ any kind of FTL drive. Not only would we have advanced theories to explain the universe but also extremely advanced computers. If we have a large number of telescopes (particularly large ones at that) across colonized space...

Well, then I don't see a problem if you're just jumping within a galaxy. We can do surveys of the Milky Way galaxy and make predictions on future locations of objects. This will have uncertainty, and there will likely be regulations on low certainty vs. high certainty jumps. 

As humans expand across the Milky Way technology and infrastructure would likely continue to advance. Observation stations will be established that regularly deliver information about star systems and positions to the appropriate authorities where it can be accessed by travelers, reducing risk substantially across human space. Eventually surveys of the Local Group's galaxies will be possible and then intergalactic jumps will be carried out, likely by unmanned vehicles initially, which will then attempt a return jump. If it succeeds then it can report on the positions of certain objects within the galaxy. If not... try again.

Of course we could just do incremental jumps using a daisy chain of jumpships between galaxies and just exchange messages, passengers, and cargo across at each stop. That way each individual jump has a lower risk until the other galaxy has been more accurately mapped.

I wouldn't be surprised if expansion to other galaxy groups and even some nearby clusters could be done over time, maybe even the entire Virgo Supercluster...

 

23 hours ago, Shpaget said:

For the first one, there is nothing intrinsic in light that can tell you anything about the distance of the source. Our distance measurements to stars rely on various methods like parallax, redshift, standard candles, etc but all require a good deal of interpretation. The light itself doesn't have a "return to" address tag.

Redshift is a change in the wavelength/frequency of light - ergo it is an intrinsic property of light being changed. I would call it an intrinsic property of light from distant objects.

Only works within a certain range of distances (on the intergalactic scale) and of course still has uncertainty.

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23 hours ago, Spacescifi said:

Helium 3, while plentiful on the moon and useful for fusion I have read that the byproducts in the exhaust are not aneutronic.

Helium-3 is not plentiful on the Moon. At all. In fact, I've found that in order to extract Helium-3 you need to spend more energy than you can get out the fusion fuel. Not only that but lunar Helium-3 is counted in the parts per billion - as in Carbon Dioxide is more plentiful in Earth's atmosphere than Helium-3 is in the lunar regolith by orders of magnitude, and even then it's difficult to extract the carbon dioxide on large scales and we're living on this rock. Processing the Helium-3 out of the regolith is a difficult process.

Lunar Helium-3 is not worth it as a fusion fuel. Though we are aware of other uses for Helium-3.

23 hours ago, Spacescifi said:

You need boron for that I read.

So unless you are picky about fuel sources, landing on planets could irradiate the landing zone.

Grav-inverters for falling upward while fiction allows one to use rockets in space and not be picky about fuel sources.

Since space is full of radiation anyway.

Helium-3 is aneutronic when used with itself, but not fully when used with other isotopes of other elements - the reason for this being random fusion events between the other isotopes, such as D-D fusion when you want D-He3 fusion. The D-D events still happen releasing neutrons.

H-Boron fusion has a massive Lawson Criterion and still isn't fully aneutronic, not to mention it can give off gamma rays.

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58 minutes ago, DDE said:

And is that a showstopper?

Milky-way pulsars don't help a lot in Andromeda,

Also, the question seemed more about finding the current location of the place where you want to go, as opposed to finding out where you are at the moment.

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18 minutes ago, kerbiloid said:

You have just made a 'long' jump and happened to end up in a galaxy of unknown size and composition.

You have data on one Andromeda pulsar and lots of Milky-way pulsars.

There is one strong near-by pulsar that is 'kind of' similar in frequency to the Andromeda pulsar, but all of that data is 2.5 million years old and it may have shifted.

Are you in Andromeda?  Some distant part of the milky-way where most of the known pulsars are not visible?

Some other Galaxy?

 

A Pulsar map is very helpful when you are in a known galaxy, but may not help a lot if you do not know which galactic cluster you are in, unless you have pulsar maps of lots of galaxies.

There is also the issue that a given pulsar may only be visible along a specific plane(directly in the beam as it were) and highly prolific, making them less useful than currently hoped. 

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