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[Serkr Team]

So even if they do about the stupidest thing possible, short of actively throwing it at the sun or dropping it from even deeper in, it's still good for 9 weeks. They could also drop it from further out or throw it outward so it falls into the sun after a couple months or years to prevent capture (24 months fall from 5 AU), but since there are essentially no natural objects on such trajectories (for obvious reasons), this is more likely to catch unwanted attention.

As I understand it from this article (which was linked to earlier in this topic) a 'good jump' will have your ship arrive around 4-5AU from the destination star, so any buoys you launch will stick around for quite some time, even if you aren't flinging them into orbit.

As I understand it Mjolnir, you're saying that the buoy sends it's little "Yo dude over here" signal when it detects a Terran ship sweeping the area with radar? (Or ladar, dradis, whatever other sci-fi scanning tech). And the ship does this as soon as it enters any system via normal procedure. This makes sense to me. Enemy probably wouldn't find it that way.

Plus assuming the bad guys find this buoy, what then? It's probably no bigger than your average space probe too, a hard target to shoot down or bring onboard. Not to mention this is the far future where they could probably fit all the needed equipment on something the size of a large toaster. And I'm assuming in Outsider-verse that most star systems are uninhabited.

[Mjolnir]

As I understand it Mjolnir, you're saying that the buoy sends it's little "Yo dude over here" signal when it detects a Terran ship sweeping the area with radar? (Or ladar, dradis, whatever other sci-fi scanning tech). And the ship does this as soon as it enters any system via normal procedure. This makes sense to me. Enemy probably wouldn't find it that way.

Exactly. The first thing you're going to do after system entry is see if you're dangerously close to something, and a scout craft will want precise information on the rest of the system as well, so it won't be short-range sensors. It's pretty trivial to embed identification information into a radar pulse or something similar. The probe gets triggered, says hello and does a cryptographic handshake with the ship, and sends its data payload. Or an unknown ship comes in, the probe stays silent, and gets ignored along with all the other inert junk in the system.

Plus assuming the bad guys find this buoy, what then? It's probably no bigger than your average space probe too, a hard target to shoot down or bring onboard. Not to mention this is the far future where they could probably fit all the needed equipment on something the size of a large toaster. :P And I'm assuming in Outsider-verse that most star systems are uninhabited.

If security's a concern, it wouldn't be hard to include a self destruct in case it is disturbed or if a ship fails authentication. It indeed wouldn't be very big at all. Sketching out a design with current tech:

• long spring-deployed whip antennas for picking up a radar pulse and determining its direction...three perpendicular dipoles, perhaps.
• radio receiver and enough of a computer to recognize its target
• laser transceiver for talking to its target
• a set of microthrusters for pointing the laser transceiver once the buoy activates
• enough solar panels to power the receiver in the area of a jump zone...about 5 AU from sunlike stars
• something like a molten salt battery to briefly power the probe up for full operation to send its data to its intended recipient

We could probably fit it all in a toaster-sized package now...all our probes have to operate a bunch of power-hungry scientific instruments and talk with Earth during their entire mission. Say the worst case distance is 15 AU...2 hours one-way lightspeed lag, hello + authentication response means it either transmits or self destructs 4 hours after activating. If it can run for 12 hours before dying, it has plenty of time for multiple attempts.

[bunnyboy]

Remember that non-directed (radio etc) emission will get weaker on range^2.
So, if you burn 1 kg of matter/antimatter in second, you get power output of 9*10^16 W.
In distance of 1 AU, this gives 300 nW/m^2, which is only about 3 times as strong as cosmic background radiation.

We could probably fit it all in a toaster-sized package now...all our probes have to operate a bunch of power-hungry scientific instruments and talk with Earth during their entire mission.

Voyager I & II use only 420 W output for all it's functions, but it's have a 3.7 meter parabelic antenna, and it works only because we both know the location of each other.

[Mjolnir]

Remember that non-directed (radio etc) emission will get weaker on range^2.
So, if you burn 1 kg of matter/antimatter in second, you get power output of 9*10^16 W.
In distance of 1 AU, this gives 300 nW/m^2, which is only about 3 times as strong as cosmic background radiation.

A few things to note:
Antennas are tuned. Most background radiation is in the microwave band, and will not couple strongly into most antennas.

Radars are generally directional, and radar pulses are a lot shorter than one second. You can get 300 nW/m^2 at 1 AU a lot easier with a beam and microsecond-long pulse. Say it's a 1 microsecond pulse at a 40 GHz (Ka-band) from a 5 meter radius parabolic dish with an aperture efficiency of 0.6. Antenna gain is pi^2*(2*5 m)^2/(c/40 GHz)^2*0.6 = ~10.5 million, the shorter pulse gives another factor of 1 million. A pulse that reaches 300 nW/m^2 at 1 AU requires radiated energy equivalent to the annihilation of 95 picograms of matter/antimatter. 8.5 kilojoules, in other words.

300 nW/m^2 is vastly more than needed. The signal from a GPS satellite is about 10 fW/m^2, about 30 million times weaker, and GPS receivers typically receive ~100 aW total due to their small, non-directional antennas. That's femtowatts and attowatts...we skipped picowatts here.

As for the Voyager probes, they also transmit at only 21.3 watts at frequencies where their dishes only have a gain of about 7.5 dBi (factor of 5.75 over an isotropic antenna), and they are currently 118 AU and 96 AU away, rather further than the 15 AU worst-case distance I mentioned. A starship's radar will certainly be more powerful and likely more directional. For actual communications, I suggested an optical link specifically due to the vastly greater link gain it allows for a given transceiver size.

Summary: yes, we probably could make one the size of a toaster without much trouble.

[bunnyboy]

Ok, I'm impressed. You are almost convinced me. You know the math & physics better than me, but haven't you ignored the fact that by tuning you need to point it right direction?
By luck, finding the probe could take years.

[Paragon]

Wouldn't they be able to figure it out pretty easily by simply knowing it's velocity and point of origin?

[Serkr Team]

Summary: yes, we probably could make one the size of a toaster without much trouble.

Will it be able to make toast?

[Mjolnir]

Ok, I'm impressed. You are almost convinced me. You know the math & physics better than me, but haven't you ignored the fact that by tuning you need to point it right direction?

No you don't. Tuning is independent of directionality. Wireless devices would be quite awkward to use otherwise.

By luck, finding the probe could take years.

The starship's going to be scanning the full hemisphere to see what's around it...where does luck come in?

Wouldn't they be able to figure it out pretty easily by simply knowing it's velocity and point of origin?

If they knew its point of origin then that alone would be sufficient. The only way for them to know that is to watch the ship launch it.

Will it be able to make toast?

The molten salt battery would operate at a temperature of a few hundred C, generally being started up by an electric heater or small pyro charge. I doubt it'd be a design feature, but modification of one to make toast should be pretty simple.

[bunnyboy]

by tuning you need to point it right direction?

No you don't. Tuning is independent of directionality.

You got me. I had either brainfart or mistranslation on that part.
I just try to say that you can't take all long range, high resolution/coverage, low energy and short time with spherical scan.

Wouldn't they be able to figure it out pretty easily by simply knowing it's velocity and point of origin?

If they knew its point of origin then that alone would be sufficient. The only way for them to know that is to watch the ship launch it.

Also a predefined or standard procedures helps to find one. Just "Look around of the biggest planet", will help a lot.

[junk]

Holy bots does this place have some sort of report function?

[TheUnforsaken]

The little ! on the bottom right hand side of the post. Arioch and the mods are pretty good and getting rid of bots though...they just have to be on to delete them.

[Michael]

hmmm, i actually understand some of the physics going on here (iv done and am doing a course in engineering, part of that was in electrical and still is) i have to say i didn't know we could use salt in a battery, but the rest about the energy usage makes sense,

of course it would be hard to find a tiny little probe thing in all that big black space, very hard, but the thing it that a ship always emits an IFF/ Identify (i think) Friend or Foe, the probe thing would pick this up if its in range and if you know where it was lunched and what way it was going at the time then its just a matter of following the trajectory till you find it, and maybe there are multiple probe things in the system for redundancy?
of course if the enemy could get one of your IFFs the system is compromised, but then that threat exists today and there would be counter measures today i guess, obviously these would therefore be more advanced in the future making it ether impossible or very unlikely to happen

[Mjolnir]

of course it would be hard to find a tiny little probe thing in all that big black space, very hard, but the thing it that a ship always emits an IFF/ Identify (i think) Friend or Foe, the probe thing would pick this up if its in range and if you know where it was lunched and what way it was going at the time then its just a matter of following the trajectory till you find it, and maybe there are multiple probe things in the system for redundancy?

I think it's reasonable to assume most spacecraft will have radar and/or lidar systems that will make those on current aircraft carriers look like toys, with which they will scan the entire sphere of surrounding space as part of normal operations...stumbling around blind is a poor way to operate any kind of spacecraft. It should be easily detectable by the probe, which can then locate the originating ship and get its attention...no need for the ship to know where the probe is or where it was launched from. I suggested a laser for the response, because it can be made very directional and thus achieve a strong signal at long range without needing a big dish antenna, making the buoy more compact.

of course if the enemy could get one of your IFFs the system is compromised, but then that threat exists today and there would be counter measures today i guess, obviously these would therefore be more advanced in the future making it ether impossible or very unlikely to happen

With the system I proposed, an enemy that successfully fakes the radar pulses that initially wake the buoy up will still have to perform a cryptographic handshake to get the buoy to report its messages. The probe sends a challenge and requires a particular response...a decrypted version of the challenge, for example, proving that the ship has decryption keys. If the ship fails the challenge, the buoy self destructs. And once launched, there's no need for a friendly ship to ever approach the buoy, so another simple precaution would be for it to self destruct if something comes within a few kilometers or so, making it rather unlikely for a buoy to be captured by unfriendly forces. The system can be made quite extremely secure.