One shot Jump Drives

Discuss the Traveller RPG and its many settings
peelseel2
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Re: One shot Jump Drives

Postby peelseel2 » Thu Mar 14, 2019 12:58 am

phavoc wrote:
Wed Mar 13, 2019 9:05 pm
.....Of course, since gravity waves propagate at the speed of light, a jump emergence detected in a system one parsec away will have occurred over three years previously, however this can still be useful in predicting traffic patterns, naval movements or the presence of a starfaring culture......The ship will also automatically detect any jump emergence within 1 parsec at the time the gravity waves reach the analysis suite.
So if you had one of these running, and a ship emerged from jump 1 parsec away, it take 3.26 years for it to register with the suite. The "Gravity wave" travels at the speed of light. It can detect stellar phenomenon at 30 parsecs because it is detecting it where it was at 30 years before. Track this object over a month or a year from 3 different systems, get the data together, and you could run a really good prediction of where it is in the now for an astrogation check and jump.
Old School
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Re: One shot Jump Drives

Postby Old School » Thu Mar 14, 2019 12:14 pm

I’m not sold on a one shot hybrid rider. The entire advantage of a rider is that it doesn’t have the fuel and drive space requirements of a starship, and therefore can be armed and armored to the teeth. However, you don’t have to go all in on the jump-4 vs rider debate. I could see a hybrid design with “riders” incorporating jump-1 or jump-2 drives in order to have the capability to flee and fight another day, but still having a jump-4 tender. If you’re going to dedicate that tonnage to fuel, you might as well install a full jump drive so as to have flexibility within your fleet.

Within a subsector navy, I could see Jump-2 designs being practical. A ship that is buil to defend a 3 or 4 system cluster doesn’t need jump 4. Jump 4 drastically lowers your firepower per credit. A tender to give them ability to keep up with the fleet when mobilized into the greater Imperium Navy (and paid for by the Imperium, not the subsector) could be an option.

If you really want to get crazy, you could go with a multiple breakaway hull design. Each rider has a jump-2 drive and fuel, and the
tender has enough drive and fuel to take the itself and the riders jump-4 or 5 when combined with the drives of the riders.
phavoc
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Re: One shot Jump Drives

Postby phavoc » Thu Mar 14, 2019 1:28 pm

For analyzing stellar phenomenon I'm fine with it. For detecting jump transits I don't think it fits well at all. Stealth jumps now make sense as standard process and equipment for all mitary vessels. Which potentially means that all military ship designs are now broken. Traveller has also always been a game system that postulates space is big and you can't watch all of it. This sort of device would make piracy very hard to practice because you could easily monitor a system for inbound or outbound ships, cross reference to known arrivals and departures in other systems and you would find your pirate bases. It would be easy to dump a sensor platform off in a system off the ecliptic and it would never be found so you would not need the long delay of putting it elsewhere.

This is an aggravating aspect of the game where the trickle effect of the books essentially renders all other designs moot as standards. I really don't think any effort is put into this because it's happened so many times over multiple versions.

As far as riders having jump drives, well, the point of a battle rider is to make them lean and mean, ton for ton, more than any other ship their size. Which makes inclusion of a jump drive, even a small one shot one, impractical and should not be included.

I get the plethora of design options, but some common sense limit needs to be applied to them in the official designs. It would be like adding a jump drive to an SDB. It's not their job function so that equipment does not belong. Making gear available to players is fine for building their own universe, though I don't think most do. That's why they buy published works so they don't have to.
peelseel2
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Re: One shot Jump Drives

Postby peelseel2 » Thu Mar 14, 2019 4:38 pm

phavoc wrote:
Thu Mar 14, 2019 1:28 pm
For analyzing stellar phenomenon I'm fine with it. For detecting jump transits I don't think it fits well at all...
It can still only detect Jump transits at the speed of light, so at the speed of all other "Long Range" detectors. It does not change how a ship would jump into the system for large navel movements. It neither increases nor decreases defense ability to react.
Condottiere
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Re: One shot Jump Drives

Postby Condottiere » Thu Mar 14, 2019 6:06 pm

Probably requires some form of minimum size to be detectable, increasing over distance.

I'd say the amount of energy used to emter hyperspace, modified by stealth; hyperspace exit would depend more on size modified by stealth.

Intervening gravity wells might well prevent detection.
phavoc
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Re: One shot Jump Drives

Postby phavoc » Thu Mar 14, 2019 6:33 pm

peelseel2 wrote:
Thu Mar 14, 2019 4:38 pm
phavoc wrote:
Thu Mar 14, 2019 1:28 pm
For analyzing stellar phenomenon I'm fine with it. For detecting jump transits I don't think it fits well at all...
It can still only detect Jump transits at the speed of light, so at the speed of all other "Long Range" detectors. It does not change how a ship would jump into the system for large navel movements. It neither increases nor decreases defense ability to react.
It's able to detect a ships entrance or exit from jumpspace at 3 light years. The fact that it "only" detects at light speed is not the issue. Something able to detect something as small as a 100 ton ship doing something 3 light years away when all the other sensors best range is 'distant' (e.g. more than 50k). Passive sensors have always been better than active, but this is insanely better.
baithammer
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Re: One shot Jump Drives

Postby baithammer » Thu Mar 14, 2019 6:56 pm

Old School wrote:
Thu Mar 14, 2019 12:14 pm
I’m not sold on a one shot hybrid rider. The entire advantage of a rider is that it doesn’t have the fuel and drive space requirements of a starship, and therefore can be armed and armored to the teeth. However, you don’t have to go all in on the jump-4 vs rider debate. I could see a hybrid design with “riders” incorporating jump-1 or jump-2 drives in order to have the capability to flee and fight another day, but still having a jump-4 tender. If you’re going to dedicate that tonnage to fuel, you might as well install a full jump drive so as to have flexibility within your fleet.

Within a subsector navy, I could see Jump-2 designs being practical. A ship that is buil to defend a 3 or 4 system cluster doesn’t need jump 4. Jump 4 drastically lowers your firepower per credit. A tender to give them ability to keep up with the fleet when mobilized into the greater Imperium Navy (and paid for by the Imperium, not the subsector) could be an option.

If you really want to get crazy, you could go with a multiple breakaway hull design. Each rider has a jump-2 drive and fuel, and the
tender has enough drive and fuel to take the itself and the riders jump-4 or 5 when combined with the drives of the riders.
A full jump 1 drive is 25% larger than a similar one-shot, at four times the cost, further the jump drive is for emergency use only as it is intended to jump out if over matched or losing the battle. ( The tender still needs jump 5 as it needs the jump 4 to reach the target system and jump 1 to either retreat if over matched or to jump out to the rendezvous point as soon as riders are deployed.

Further, jump 2 takes a big enough bite out of a rider to hinder its efficient use of displacement at 250% increase in drive displacement and 100% increase in displacement needed for fuel.

Subsector navies should be using jump 4 as it services a large enough section of the Imperium and are expected to interoperate with the Imperial navy, world navies are a different matter entirely.

The breaking up the jump drive into 1 tender / 2-3 riders is highly inefficient.
peelseel2
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Re: One shot Jump Drives

Postby peelseel2 » Thu Mar 14, 2019 7:15 pm

phavoc wrote:
Thu Mar 14, 2019 1:28 pm
It's able to detect a ships entrance or exit from jumpspace at 3 light years. The fact that it "only" detects at light speed is not the issue. Something able to detect something as small as a 100 ton ship doing something 3 light years away when all the other sensors best range is 'distant' (e.g. more than 50k). Passive sensors have always been better than active, but this is insanely better.
Again, if the 100 dton ship exits jumpspace 3 light years away, it is going to be 3 years later it detects it. I'll take the sensors at 50k. As a long term 'ear' the "gravity wave" detector works great. As a short term I just jumped to 100 diameter limit, the sensors packages are great.

relevant rules quotes:
".....Of course, since gravity waves propagate at the speed of light, a jump emergence detected in a system one parsec away will have occurred over three years previously, however this can still be useful in predicting traffic patterns, naval movements or the presence of a starfaring culture......The ship will also automatically detect any jump emergence within 1 parsec at the time the gravity waves reach the analysis suite."

The key is that all sensors, lasers, radio signals, IR signatures, visual light bounce, "gravity waves", etc. travel at the speed of light.
phavoc
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Re: One shot Jump Drives

Postby phavoc » Thu Mar 14, 2019 7:30 pm

peelseel2 wrote:
Thu Mar 14, 2019 7:15 pm
Again, if the 100 dton ship exits jumpspace 3 light years away, it is going to be 3 years later it detects it. I'll take the sensors at 50k. As a long term 'ear' the "gravity wave" detector works great. As a short term I just jumped to 100 diameter limit, the sensors packages are great.

relevant rules quotes:
".....Of course, since gravity waves propagate at the speed of light, a jump emergence detected in a system one parsec away will have occurred over three years previously, however this can still be useful in predicting traffic patterns, naval movements or the presence of a starfaring culture......The ship will also automatically detect any jump emergence within 1 parsec at the time the gravity waves reach the analysis suite."

The key is that all sensors, lasers, radio signals, IR signatures, visual light bounce, "gravity waves", etc. travel at the speed of light.
You are missing the point. The ability to detect anything as small as a 100dton craft at 3 light years is a HUGE thing. Thank goodness they didn't make it even worse by trying to make the sensors faster than light. You could easily place a detector and/or ship in an enemy system at 100AU and never be found (your jump trace will by these sensors). Knowing how often ships deploy from nodal bases is great for an attacker. And no, a defender isn't going to just randomly have ships enter/depart just to mess with tracking. Militaries don't work that way in reality. For specific periods during wartime to confuse an enemy? Yes, many things are possible. But as a normal mode of operation? No, they don't do that.

It's not stated just how accurately you can place the entry/exit of ships from a distance. Can you plot their exact location? Within 10,000km? Clearly some sort of locus is possible based on the text description. If you can detect a cometary object at 1/10th of a parsec, and they have zero jump drives, then I'd say your capability of plotting is more refined than less.

You also miss the point that every military ship now needs stealth to stop it from being tracked. Intelligence is very valuable. No star nation will want an enemy to be able to easily understand how many transits are taking place (the sensors know how many enter/leave).

The key is that it's even possible to do this, regardless of the range.
peelseel2
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Re: One shot Jump Drives

Postby peelseel2 » Thu Mar 14, 2019 8:36 pm

phavoc wrote:
Thu Mar 14, 2019 7:30 pm
You are missing the point. The ability to detect anything as small as a 100dton craft at 3 light years is a HUGE thing. Thank goodness they didn't make it even worse by trying to make the sensors faster than light. You could easily place a detector and/or ship in an enemy system at 100AU and never be found (your jump trace will by these sensors). Knowing how often ships deploy from nodal bases is great for an attacker. And no, a defender isn't going to just randomly have ships enter/depart just to mess with tracking. Militaries don't work that way in reality. For specific periods during wartime to confuse an enemy? Yes, many things are possible. But as a normal mode of operation? No, they don't do that.

It's not stated just how accurately you can place the entry/exit of ships from a distance. Can you plot their exact location? Within 10,000km? Clearly some sort of locus is possible based on the text description. If you can detect a cometary object at 1/10th of a parsec, and they have zero jump drives, then I'd say your capability of plotting is more refined than less.

You also miss the point that every military ship now needs stealth to stop it from being tracked. Intelligence is very valuable. No star nation will want an enemy to be able to easily understand how many transits are taking place (the sensors know how many enter/leave).

The key is that it's even possible to do this, regardless of the range.
Don't think I'm missing the point. So I can detect ships going into and out of a system 3 years late. It does not tell me the type, where they came from, where they are going. It gives me a traffic count. Spies could probably get me more information. Spy satellites could get me more information. "What are those satellites in the same orbit as the Gas Giant? Oh, those are registered to GenDevCo for a spectral emissions study? They have a license for that? Oh, Ok...."

Anything sitting at 100 AU which is powered (like sensor probes, satellites, SHIPS, etc.) are going to light up like a light bulb. Heat dissipation in space is a VERY real problem. Even without a "gravity wave" detector sitting there, you are going to know they are their. Right now we can pick out small kuiper belt objects with dispersed telescopic arrays with light reflection only.
Imagine if they where powered and reacted against the solar wind. They may be able to sit their for a day or two before being noticed, but they will be noticed.

I think as written the Gravity wave detector is not a very powerful thing.
Old School
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Re: One shot Jump Drives

Postby Old School » Thu Mar 14, 2019 8:56 pm

Anything sitting at 100 AU which is powered (like sensor probes, satellites, SHIPS, etc.) are going to light up like a light bulb. Heat dissipation in space is a VERY real problem. Even without a "gravity wave" detector sitting there, you are going to know they are their. Right now we can pick out small kuiper belt objects with dispersed telescopic arrays with light reflection only.

While I don’t doubt this is true true in reality with today’s technology, it also breaks all the sensor rules of the game we are discussing.

If ships at huge distances are so easily detected, the concept of picking up jump signatures in system suddenly becomes irrelevant. Switching off your transponder to sneak up on a ship with civilian sensors? Formidable sensor checks beyond 300,000 km?
Reynard
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Re: One shot Jump Drives

Postby Reynard » Thu Mar 14, 2019 9:10 pm

"product of desperate shipyards, jump drives can be constructed to be used just once. With many corners cut in both design and manufacture, it is a brave Traveller who entrusts their voyage and life to these drives..."

So the desperate build them and the insane use them making them plot-device rare except for travellers who have excess credits and truly believe they have the necessary skill or so the urban legend goes.

"Are you kidding?! I'm the only one to make the Sindal Run using a one shot drive!"
phavoc
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Re: One shot Jump Drives

Postby phavoc » Thu Mar 14, 2019 9:14 pm

peelseel2 wrote:
Thu Mar 14, 2019 8:36 pm
Don't think I'm missing the point. So I can detect ships going into and out of a system 3 years late. It does not tell me the type, where they came from, where they are going. It gives me a traffic count. Spies could probably get me more information. Spy satellites could get me more information. "What are those satellites in the same orbit as the Gas Giant? Oh, those are registered to GenDevCo for a spectral emissions study? They have a license for that? Oh, Ok...."

Anything sitting at 100 AU which is powered (like sensor probes, satellites, SHIPS, etc.) are going to light up like a light bulb. Heat dissipation in space is a VERY real problem. Even without a "gravity wave" detector sitting there, you are going to know they are their. Right now we can pick out small kuiper belt objects with dispersed telescopic arrays with light reflection only.
Imagine if they where powered and reacted against the solar wind. They may be able to sit their for a day or two before being noticed, but they will be noticed.

I think as written the Gravity wave detector is not a very powerful thing.
Sitting at 100AU a ship is invisible to all sensors. And since the gravity wave detector is apparently passive it's not emitting anything to detect. To detect it passively based on IR is akin to finding tiny needle in a humongous haystack. This assumes you also don't have a method of taking your heat and converting it to energy. Which is not impossible since it's how Voyager probes are powered, through radioisotope thermoelectric generators. Efficiency may suck, but as long as you can convert your heat into energy and dump it out, say via an X-ray laser, your radiant heat is reduced, thus your IR signature is reduced. I'm not saying it's going to be perfect, but as long as you don't light up like a flare then you are doing what you want it to do. As far as I know it's not been used on the ISS (they use ammonia-based heat radiators - then again they aren't trying to hide either), so experiments in space have been limited to RTG's on deep-space probes.

Detection of Kuiper objects is based on occultation (e.g. one item passes in front of another) like you say. For this particular instance you can park behind a comet and you are invisible to all sensors (including IR) based in the system. So known objects work in your favor as they would automatically be excluded when doing a scan. And the sky is BIG. The amount of space you have to scan on a continuous basis is just staggering. While it's a detection method, it's severely limited.

And, as you say, it's light-speed limited too. The data is old by the time you get it and it would be at least a week to get to the location and investigate. By then the vessel could have moved out of sensor range to park behind another object - this is assuming on the off-chance you would even be investigated. Detection just means an object occluded a star. Was it a body passing through the kuiper belt? Was it a previously uncharted asteroid or object a few hundred meters in diameter? It would be improbable for any navy to chase down every object.
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Re: One shot Jump Drives

Postby Condottiere » Thu Mar 14, 2019 9:28 pm

Seventy five percent discount isn't large enough to risk one shot jump drives beyond the initial transition, or even to bother building them in the first place.

I will speculate that the manufacturing process is replacing some or more vital element(s) with a cheaper and less durable substitute(s).
baithammer
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Re: One shot Jump Drives

Postby baithammer » Fri Mar 15, 2019 8:28 am

I think people have missed the point about the array as it detects the jump in and out of system, not the ship itself.

Also a major woosh on the one shot drives.

The one shot drive is for emergency usage, ie most of the time not going to be used. ( Hence the 75% discount being a big incentive.)

Further, the point is to use a breakaway hull for the one shot drive so your not forced to overhaul the entire ship to replace it. ( All the other components in the jump drive section are reusable.)
Old School
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Re: One shot Jump Drives

Postby Old School » Fri Mar 15, 2019 10:56 am

With a one shot on the breakaway section, your ship still need a standard jump drive that has the tonnage to support the entire craft, including the breakaway section. That makes your one shot on the breakaway section is redundant.

The breakaway section should have enough drive to support its tonnage, and the entire craft enough jump drive, including the part that is on the breakaway hull, to support the entire craft. I.e. the jump drive for the breakaway is part of the jump drive for thr entire vessel.

You getting a 75% discount on somthing that is not in any way needed, and therefore a waste of money and space. Only if your house rule is that the two sections can’t combine their drives does the one shot start to make sense for a breakaway hull.
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Re: One shot Jump Drives

Postby baithammer » Fri Mar 15, 2019 6:12 pm

With a one shot on the breakaway section, your ship still need a standard jump drive that has the tonnage to support the entire craft, including the breakaway section.
No you don't as the one shot drive is sized for both sections, which doesn't need another drive.

It is needed in the case of a rider as it gives the rider the ability to have limited jump capability outside of the tender, which removes its major achilles heel.
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Re: One shot Jump Drives

Postby Reynard » Fri Mar 15, 2019 8:02 pm

That Achilles Heel was what sold the whole concept of battle rider designs, many fast, armored and well armed ships in the heat of battle while their jump engine waits safely. With all the other support vessels. As soon as you add crap drives 'just in case' you degrade the advantage.

The description of one jumps make it clear these are not common for obvious reasons and I'm sure most military ship architects dismissed them a long time ago. Can you imagine 21st century ships using one shot systems to trim the budget?
Condottiere
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Re: One shot Jump Drives

Postby Condottiere » Fri Mar 15, 2019 8:06 pm

Maintenance cost is zero point one percent per annum, which could be under three thousand bux for a ten tonne drive.
baithammer
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Re: One shot Jump Drives

Postby baithammer » Fri Mar 15, 2019 8:48 pm

Reynard wrote:
Fri Mar 15, 2019 8:02 pm
That Achilles Heel was what sold the whole concept of battle rider designs, many fast, armored and well armed ships in the heat of battle while their jump engine waits safely. With all the other support vessels. As soon as you add crap drives 'just in case' you degrade the advantage.

The description of one jumps make it clear these are not common for obvious reasons and I'm sure most military ship architects dismissed them a long time ago. Can you imagine 21st century ships using one shot systems to trim the budget?
The achilles heel wasn't what was sold, what was sold is the more efficient use of space in the individual weapons platforms by leaving the jump drive in separate hull.

The achilles heel was the inability to withdraw in the event of being overmatched or losing the battle as they can't jump out on their own, as well as the vulnerability of the tenders allows a mission kill by enemy strike ships end running the tenders.

By using the one shot drive, you allow for the minimum size / cost for the jump capability and the tender doesn't need to stay in system any longer than dropping off the riders.

The result is between a hybrid rider ( Full jump 1 drive) and regular rider.

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