using spaceships for battletech-style tactical mecha combat

[Rolando]

Originally Posted by AlexanderHowl

The advantage of a tank is that they can devote a lot of their systems to armor and sloping allows them to deflect the force of attacks much more effectively than flat armor from a single direction (forward in most cases). Sloped armor could probably be included as a feature without that much effort (multiplying the cost of the armor by the multiplier of the DR from one direction for the armor of one section, with a maximum multiplier of twice the number of armor components in that section). For example, a TL9 SM+6 tank with six front advanced metallic laminate armor components could increase their effective forward DR for the front section by up to 12x through spending 12x as much on each armor component, resulting in an effective forward dDR 360 (for a total cost of $14.4M). Of course, it would only have dDR 30 against attacks from any other direction against the front hull.

You can multiply the armor dDR by multiplying the cost?
That can help and explain a lot. Still seems a lot like hanwave but at least is a system integrated handwave.

[ericthered]

A while back I did an analysis of spaceships armor and came to the conclusion that the values were about a third of what they should be to be competitive with human armors.

Another thing to remember is that spaceships is based on mass, not volume. Pyramid 34 gives conversions for vehicles with extra armor. And for armoring one side more than another, which tanks also do.

[Rolando]

But that still makes the T-72 a better choice than a TL9 armored combat vehicle, unless you can multiply the armor as AlexanderHowl says above.

All the mechas I have seeing are very weak in comparison to vehicles 2 tech levels (!) below.

Is there a way to fix that?

As far as I can see making a tank will give similar results, even by bunching most of the armor at the front. Unless you can make a x12 multiplier (or at least a x6) of the armor.

[Rupert]

Most spaceships designed using Spaceships have a fairly low amount of their mass devoted to armour. A modern tank, on the other hand, has about 50% of its mass devoted to armour, and this has been trending upwards as extra layers, reactive armour modules, etc. have been retro-fitted to them.

A modern MBT has a mass that puts it somewhere between SM+5 and SM+6 in SS. They are not streamlined. Thus with TL8 metallic laminate each system (5% mass) would provide about dDR4, or DR40 to 1/3 of the vehicle. Using Pyramid 3/34's 'armor and volume' rules ten systems multiplies DR by x1.5. Using 'armor by facing' we double the total DR and then split it between the six facings (front, left side, right side, rear, top, bottom).

So: 40 x 10 x 1.5 x 2 = 1200. That's about 2/3rds what a T-72 has, and about double what a WWII medium has. If we spread it out something like: Top, bottom: DR70, sides, rear: DR120, front: DR700 we get something with a lot more frontal armour than a WWII medium, and a little more armour everywhere else.

I don't think that's too bad for a system designed for spaceships that have lots of fuel tanks, living spaces, and other high-volume, low-mass systems. Note that the tanks in HT are SM+4, but have the mass of a SM+5 to SM+6 vehicle. Also, ten systems for armour leaves three for crew, three for weapons (and that's probably excessive), and four for engines and tracks, which is about right (using gas turbines and the smaller systems rules you could make a case for two systems of engines, or you could slow the tank down and only use two anyway), so it works out that way too.

Using eleven armour systems increases the DR available by 17%, and it can all go on the front, increasing frontal armour to about DR900. Using twelve armour systems, there's 44% more DR, and frontal DR can be about DR1200, and the armour is now somewhat comparable to a T-72, though it's a TL higher.

I don't think the numbers are way off, all things considered.

EDIT: By the way, sloping armour does not give you significantly more DR per unit of mass.

[AlexanderHowl]

Originally Posted by Rolando

You can multiply the armor dDR by multiplying the cost?
That can help and explain a lot. Still seems a lot like hanwave but at least is a system integrated handwave.

Armor DR for one facing (forward, backward, top, bottom, right, or left) could be improved at higher costs (the cost multiplier is indicative of the better materials and higher quality labor required for effective sloped armor).

[Rolando]

That is what I'm seeing. The main problem is trying to make spaceship tanks instead of starting with a ground vehicles construction system.

I think I'll wait for a consolidated vehicle construction system or at least a mecha and ground vehicles construction one. Meanwhile fudging with the older 3e Mecha/Robots/Vehicles books will be better, as I already have them.

Compatibility to 4e equipment will have to be handwaved somehow. I may simply not use the spaceship stats or multiply their dDR by an appropriate value for my setting.

[ericthered]

Originally Posted by Rolando

As far as I can see making a tank will give similar results, even by bunching most of the armor at the front. Unless you can make a x12 multiplier (or at least a x6) of the armor.

Originally Posted by Rolando

Compatibility to 4e equipment will have to be handwaved somehow. I may simply not use the spaceship stats or multiply their dDR by an appropriate value for my setting.

Originally Posted by Rupert

So: 40 x 10 x 1.5 x 2 = 1200. That's about 2/3rds what a T-72 has, and about double what a WWII medium has. If we spread it out something like: Top, bottom: DR70, sides, rear: DR120, front: DR700 we get something with a lot more frontal armour than a WWII medium, and a little more armour everywhere else.

I don't think that's too bad for ...

Multiply by three folks. It will sort most of these issues out, including 4e equipment compatibility and making tanks built as Rupert demonstrates using pyramid 34 just a bit better than their official counterparts.

[Anthony]

There are a couple of issues that cause spaceships DR to be surprisingly low.

The first is just that spaceships assumes a typical density equal to a surface ships. Armored vehicles are much denser than that.

The second is that high and ultratech armor is hilariously excessively good, largely because modern armor is grossly overrated (it should be semi-ablative with something like 2/6 coverage) and then ultratech armor had to have similar bloated stats to look competitive. A TL 9 combat hardsuit has a total coverage of around 18 square feet and provides DR 30, with another DR 20 on the torso (about 5 more square feet) for a total of 640 sf*DR, all at a weight of 30 lb, meaning the weight per unit DR is a bit under 0.05 lb/sf*DR. RHA is about 0.56 lb/sf*DR, so the hardsuit is something like 12x better. By comparison, TL 9 advanced metal laminate is 3x the DR of TL 7 steel.

[ericthered]

Originally Posted by Anthony

The second is that high and ultratech armor is hilariously excessively good, largely because modern armor is grossly overrated (it should be semi-ablative with something like 2/6 coverage) and then ultratech armor had to have similar bloated stats to look competitive.

On the other hand, if you extrapolate all the way down, spaceships claims that 30 lbs of steel armor evenly distributed over SM+0 should give DR 2, which is quite low. So its not just an ultra-tech and high-tech problem.

[Anthony]

Originally Posted by ericthered

On the other hand, if you extrapolate all the way down, spaceships claims that 30 lbs of steel armor evenly distributed over SM+0 should give DR 2, which is quite low.

Eh, it's not a lot low; it's around 1.5 lb/sf, which is DR 2.7 for RHA.