HG 2e Solar Panel p. 36 question

[AnotherDilbert]

Why don't we look at an electroactive polymer wire embedded in the fabric of the solar array.

Yes, that sounds at least theoretically workable.

a quantum dot solar cell would be about 400-500 Nm thick..if the article I read is accurate... and a sheet of paper is 100,000 nanometers thick... if only 50% of the volume of the array was the nano-cell array that would leave half the volume for the spool, EAP fibers and wiring.

At a guess a material that is 0,0005 mm thick would be shredded by a slight vibration, much tell being rolled up. I suspect it would have to be attached to a sturdier film of some kind.

 

[AnotherDilbert]

... having a panel of solar cells, which resemble a sail, collecting energy and diverting that to the manoeuvre drive, would make a craft so equipped faster than one with an actual solar sail.

M-Drives are remarkably energy efficient, so I believe you are right.

But to keep the solar cells intact, we would have to use very small accelerations, perhaps 0,01 G?

 

[phavoc]

The rules don't specifically go down this rabbit hole, but if the drives can function under micro-power, then it would be possible to say engage them at .1, or even .05G. While you won't be able to zip through space at your normal expected rates, you will still be able to potentially get to your destination if it's in-system. Continuous acceleration is a wonderful thing.

 

[AnotherDilbert]

It should be possible? M-Drives produce thrust, the rest is Newton at work.

 

[phavoc]

It should be possible? M-Drives produce thrust, the rest is Newton at work.

Agreed. The only issue might be that in order for the drive to function at all it needs 100% power to activate. There are some things that if you don't meet the minimum they just don't work.

 

[fusor]

In TNE at least (since that gives us actual real power requirements in megawatts, not "power points"), the default was that 10 tonnes of thrust was required per dt of ship volume to have an acceleration of 1G.

So to have a 100dt ship accelerate at 1G, you needed 1000 tonnes of thrust.

Each cubic metre of Thruster Plate generates 40 tonnes of thrust and requires 1 MW of power.

So you'd need 25 cubic metres (and 25 MW) of Thruster Plates to get 1000 tonnes of thrust, which would be able to accelerate your 100dt ship to 1G.

How big a solar panel (or solar sail) do you think you'd need to generate 25MW of power? (hint: it'd be really really big).

 

[Condottiere]

Motors tend to be optimized for a certain performance range, whether low speed or high speed.

Efficiency degrades once you push them out of that, which Traveller engineering doesn't take into account.

 

[AnotherDilbert]

So to have a 100dt ship accelerate at 1G, you needed 1000 tonnes of thrust.

Quite, but to achieve 0,01 G you only need 100 kN of thrust. And the huge flimsy solar panel might withstand it.

 

[fusor]

Motors tend to be optimized for a certain performance range, whether low speed or high speed.

Efficiency degrades once you push them out of that, which Traveller engineering doesn't take into account.

"Motors" aren't involved in Thruster plates. Electricity is directly converted to movement, so it's hard to see where that sort of limitation would show up.

 

[fusor]

So to have a 100dt ship accelerate at 1G, you needed 1000 tonnes of thrust.

Quite, but to achieve 0,01 G you only need 100 kN of thrust. And the huge flimsy solar panel might withstand it.

OK, so you need 0.25 MW instead. That's achievable with a solar panel (it's more ISS-scale)... but it's also comparable to the thrust you'd get from a solar sail on its own anyway.

If you want slow accelerations, just use an ion drive or a solar sail. Using a solar sail to power thruster plates is pointless.

 

[AnotherDilbert]

So to have a 100dt ship accelerate at 1G, you needed 1000 tonnes of thrust.

Quite, but to achieve 0,01 G you only need 100 kN of thrust. And the huge flimsy solar panel might withstand it.

OK, so you need 0.25 MW instead. That's achievable with a solar panel (it's more ISS-scale)... but it's also comparable to the thrust you'd get from a solar sail on its own anyway.

If you want slow accelerations, just use an ion drive or a solar sail. Using a solar sail to power thruster plates is pointless.

Wiki says a solar sail of 800 m × 800 m = 640000 m2 can achieve a thrust of 5 N, so to get 100 kN we need 20000 × 640000 m2 = 12800 square km solar sail (roughly the size of Yorkshire or Connecticut). Solar sails also have a problem with vectoring.

A 48 kg NSTAR ion thruster produces a thrust of 92 mN using 2,3 kW. To get 100 kN we would need over 1 000 000 NSTAR units massing 48 000 tonnes and using 2,5 GW power. We would also need hundreds of thousands tonnes of reaction mass. We would fail to mount that in a 100 dT hull. Ion drives are much less efficient than M-drives.

M-drives are extremely efficient, if we have them we will use them where-ever we need thrust.

 

[fusor]

M-drives are extremely efficient, if we have them we will use them where-ever we need thrust.

We're talking about "Thruster Plates" - not "M-Drives". Thruster Plates are a specific type of M-Drive (Manoeuvre Drive) and are the default ones assumed in most version of Traveller (excluding TNE, where they're an alternative technology). But yes, they're very efficient.

Remember that Traveller ships are huge by modern standards, and therefore way more massive - ion drives and solar sails just aren't practical for ships that big (unless you really want them to take a long time to get somewhere). But for tiny payloads that you're in no rush for? Solar sails, solar panels, RTGs, and ion drives would work as well as they do today (if not better).

 

[Condottiere]

Costs are linear, so time is money.

 

[snrdg121408]

Hello fusor,

In TNE at least (since that gives us actual real power requirements in megawatts, not "power points"), the default was that 10 tonnes of thrust was required per dt of ship volume to have an acceleration of 1G.

So to have a 100dt ship accelerate at 1G, you needed 1000 tonnes of thrust.

Each cubic metre of Thruster Plate generates 40 tonnes of thrust and requires 1 MW of power.

So you'd need 25 cubic metres (and 25 MW) of Thruster Plates to get 1000 tonnes of thrust, which would be able to accelerate your 100dt ship to 1G.

How big a solar panel (or solar sail) do you think you'd need to generate 25MW of power? (hint: it'd be really really big).

MT Referee's Manuel Power Supplies provide requirements in kilowatts.

 

[fusor]

MT Referee's Manuel Power Supplies provide requirements in kilowatts.

Valid point .

It looks like each unit of Thruster Plate in MT is 1dt in volume, and produces 500 tonnes of thrust for a 100dt ship (each cubic metre would be 35-40 tonnes of thrust, which is close enough to the 40 from TNE), assuming the thrust required for 1G is still a 10x ship volume). And the power requirements would be higher in MT too (more like 5 MW per cubic metre of Thruster Plate). Though weirdly the volume of drive required for higher accelerations doesn't scale linearly, for a 100dt ship they seem to be adding (G-1) units to the calculated value (and that changes with higher ship tonnage).

I'd go with the TNE version, it's more straightforward and consistent.

 

[snrdg121408]

Morning PDT fusor,

MT Referee's Manuel Power Supplies provide requirements in kilowatts.

Valid point .

It looks like each unit of Thruster Plate in MT is 1dt in volume, and produces 500 tonnes of thrust for a 100dt ship (each cubic metre would be 35-40 tonnes of thrust, which is close enough to the 40 from TNE), assuming the thrust required for 1G is still a 10x ship volume). And the power requirements would be higher in MT too (more like 5 MW per cubic metre of Thruster Plate). Though weirdly the volume of drive required for higher accelerations doesn't scale linearly, for a 100dt ship they seem to be adding (G-1) units to the calculated value (and that changes with higher ship tonnage).

I'd go with the TNE version, it's more straightforward and consistent.

I was mentioning that MT calculated output power in a unit of watts prior to TNE. However, neither, at least in my opinion, MT or TNE correlates to CT LBB 5 energy points. Mongoose appears to have followed CT LBB 5 for HG 2e.

 

[fusor]

I was mentioning that MT calculated output power in a unit of watts prior to TNE. However, neither, at least in my opinion, MT or TNE correlates to CT LBB 5 energy points. Mongoose appears to have followed CT LBB 5 for HG 2e.

I hate "power points" - if they're going to break down power output into units then why on earth don't they just use real units of power? Do publishers think that people are too stupid to handle that or something? Are they just terrified of science? Adding another abstraction layer just makes it unnecessarily opaque. Is there even any logic to how many PP are equivalent to say 1 MW? (I guess one would have to look at MT and TNE and compare their values with the ones in HG 2e)

 

[-Daniel-]

I was mentioning that MT calculated output power in a unit of watts prior to TNE. However, neither, at least in my opinion, MT or TNE correlates to CT LBB 5 energy points. Mongoose appears to have followed CT LBB 5 for HG 2e.

I hate "power points" - if they're going to break down power output into units then why on earth don't they just use real units of power? Do publishers think that people are too stupid to handle that or something? Are they just terrified of science? Adding another abstraction layer just makes it unnecessarily opaque. Is there even any logic to how many PP are equivalent to say 1 MW? (I guess one would have to look at MT and TNE and compare their values with the ones in HG 2e)

Or the publisher is trying to avoid the very "this rule is broken because of the science I know" kinds of rejections that happen all the time to RPGs that do use real world measures. I think of the Star Trek idea of the transporters. They just work in the setting because the creator of that setting said they do. No need to justify the science behind it. So when I say a Power Plan produces 25 power points it just does. No arguments. But if I say it produces 25 Gigawatts, then I am subjected to arguments like "no way your power plan at that size could produce that amount of power".

Not saying I agree or disagree, just that the motive to keep the "science" vague could be based around a desire to avoid the fetching, moaning, and hand wringing that can follow many RPGs.

Just a thought. :mrgreen:

 

[AnotherDilbert]

I was mentioning that MT calculated output power in a unit of watts prior to TNE. However, neither, at least in my opinion, MT or TNE correlates to CT LBB 5 energy points. Mongoose appears to have followed CT LBB 5 for HG 2e.

1 HighGuard'80 EP = 250 MW.

1. Lasers: A shipboard laser is a beam or pulse laser with an input of 250 megawatts. The pulse laser has 3 lenses.
2. Plasma and Fusion Guns: A ship's plasma gun has in input of 250 megawatts; a fusion gun has an input of 500 megawatts.

Striker, Book 2, p41.

 

[fusor]

But if I say it produces 25 Gigawatts, then I am subjected to arguments like "no way your power plan at that size could produce that amount of power".

Nobody's said that though, so that's a bit of a strawman. Solar panels are definitely not a "high power output" thing so those stand out, but a fusion plant with output in the hundreds of MW is fine. But if you just talk about PP then you get nonsense like solar panels being equivalent to a significant percentage of the output of a fusion plant, which is bonkers because then numbers are just being pulled out of thin air for an arbitrary unit.