DGP 101 Vehicles

[Major B]

I recently started tinkering with reverse-engineering the Trepida design in 101 Vehicles and had some difficulty due to what I think are errors in the listed UCP.

Since DonM's errata will now include DGP material, I thought a new thread to discuss 101 vehicles might encourage others to take a look and see what errata is there to be found.

I'd also like to discuss some vehicle design philosophy while we're at it, since some of my problems with the Trepida aren't necessarily errata but rather just poor design. Well, at least a poor design in my opinion, other may disagree and that is why I'd like to see some discussion.

The most glaring errors I spotted on the Trepida (#32 - on the front cover, inside):

1. Hull damage points are listed as 12/29 and displacement is listed as 10 Td. According to the formula on page 84 of the RM, hull damage points are calculated from hull volume (H). Inop is derived as H/15 and destroyed is H/6 (both round up). Since 10 Td = 135 kl, the hull damage points should be 9/23.

2. Object Size is listed as small and loaded weight is listed as 125 tons. According to page 89 of the RM, object size is derived from loaded weight. Objects between 100 and 10,000 tons are "average" while those less than 100 tons are "small" so the size of the Trepida should be listed as average.

3. The vehicles max acceleration is listed as .9 G and thrust is listed as 400 tons. According to the formula on page 86 of the RM, maneuver thrust = (thrust/loaded weight)-1. So the listed max acceleration should be (400/125)-1 or 2.2 G.

Check my work - does this look right to everybody?

Next post will have some design philosophy questions for discussion.

 

[Major B]

Trepida design shortcomings

As I mentioned in the OP, the Trepida has many shortcomings that aren't necessarily errata. What kind of gnaws at me is that the Trepida is described as "the standard issue grav tank" (emphasis added) when the design (to me) seems very poor.

Here's some items I'd like to discuss:

1. Why only 40G for armor? It can be penetrated by many large-bore CPR weapons (even medium-bore at higher TLs), 25MW and larger lasers (including TL8 designs), and every Plasma and Fusion gun. Survivability for this design seems to be its biggest shortcoming.

2. Why only one weapon system? There is no coaxial suppressive weapon or a laser that might provide longer range. No backup if the main gun goes down. No high-ROF anti-personnel weaponry. No auxiliary weaponry with point defense capability. This, coupled with weak armor, makes the Trepida extremely vulnerable to infantry with tac missiles and indirect-fire systems with HEAP warheads.

3. Communications capabilities are weak. No ability to communicate with vessels in orbit and the only comm system with range greater than 5k is a radio which allows the enemy to target you whenever you use it.

4. Sensors are weak. If the vehicle could communicate with sensor platforms in orbit that would be excusable, but no. As it stands, the Trepida has no passive object scan or pin ability, passive energy scans are formidable, and active scan and pin are formidable. So the Trepida cannot easily acquire targets except visually, so the main armament's range of 18 km is effectively reduced to 5 km (the range of the active EMS system) except when it can visually acquire a target.

Bottom Line: Neither survivable nor effective. Okay, maybe the design was intended only as a role-playing device rather than a wargaming system, but the design stats are there so the vehicle can be used in the game so the design should at least try to approximate an effective combat vehicle design, and this one is not that.

But that's my opinion. What do you think?

 

[Border Reiver]

Just a quickie. The actual displacement for a Trepida is 13dton. It is 10dton hull plus 30% for the turret.

This gives the 12/29 score printed (well sort of, if it is round up rather than round off then it should be 12/30)

TNE adds a VRF gauss coaxial mount to the armament.

40G. Well that was the minimal armour for vacuum ops. Don't forget that in MT the penetration of any weapon drops by 50% for its range attenuation. This means the armour is ample for most combat. Remember an RPG7 can (and has) taken out an M1A1 at 50m ranges.

 

[Major B]

Just a quickie. The actual displacement for a Trepida is 13dton. It is 10dton hull plus 30% for the turret.

This gives the 12/29 score printed (well sort of, if it is round up rather than round off then it should be 12/30)

That makes sense, but causes another problem. First, makes sense because part of the problem I was having in reverse engineering the design from the UCP was the size of the turret - couldn't make it fit within the 10 Td listed. But, that's the problem. The Trepida and the Astrin are supposed to be identical in displacement (I'd assumed anyway) because any combination of four Astrins and Trepidas can fit in the Rapid Deployment Aeroshell described on page 17 (vehicle 33 - Astrin APC). This aeroshell design was the reason I was working on the reverse engineer of the Trepida and I planned to do the Astrin next.

TNE adds a VRF gauss coaxial mount to the armament.

That makes good sense. Do you think I should include that in the final design I come up with?

40G. Well that was the minimal armour for vacuum ops. Don't forget that in MT the penetration of any weapon drops by 50% for its range attenuation. This means the armour is ample for most combat. Remember an RPG7 can (and has) taken out an M1A1 at 50m ranges.

Good point, and good illustration too. I've seen some penetrations of the M1 first hand. That mitigates the effectiveness of the plasma and fusion guns, but they still have the listed penetration out to 5 km since their attenuation is 5. Lasers are mitigated more, since their pen is halved after 500m (attenuation is 4). But CPR HEAP reounds (like that on the RPG7) do not attenuate so can still penetrate out to the effective range of the system. So maybe I was a bit too strong, but I still think heavier armor is needed for survivability within the 5 km range as is a point defense system to protect against indirect fire and missiles/rockets with HEAP warheads.

 

[Ranger]

Well, another problem is that the MT design system forced you to essentially establish an average armor rating for the entire hull, rather than the Striker system, which let you put specific armor thickness on specific parts of the vehicle. Given that the Trepida is basically a triangle, I would imagine that the armor of the front would be much thicker, and that the high angles of incidence to a forward attack would make the effective armor thickness even greater. The problem is that those factors get lost in the MT design system.

 

[far-trader]

Well, another problem is that the MT design system forced you to essentially establish an average armor rating for the entire hull...

It's been a while but I recall MT vehicle armor including slope? Not different armor on faces but modifiers to the base armor for face slopes, and lost volume for the slopes. Or am I confusing MT with some other (non-Striker) Traveller vehicle design system?

 

[aramis]

No, FT, you're confounding it with Striker!

 

[far-trader]

No, FT, you're confounding it with Striker!

Possibly I just don't recall doing a lot of Striker designs, but I do recall several vehicle designs that did involve sloped armor And I did do several in MT. Maybe it wasn't even Traveller. This is gonna bug me now I'll sleep on it, maybe a memory will jog loose.

It hit me before heading for bed. TNE FF&S1

Apologies for the brain fart and thread drift.

 

[Ranger]

I dug this out of my old saved files. Not sure where I got it originally, but it's a quick and easy way to adjust armor values for MT vehicles. I've edited it down to just the formula.

A LOOK AT ARMOUR FACINGS

Document No: 181.14

By Stuart Machin

To remedy this gap in the rules (which became readily apparent in an adventure when a single APC took on a platoon of well equipped soldiers and killed every single one), I have devised a rough and ready set of guidelines. Other players may feel that the single set of parameters are too constrictive, and they are encouraged to develop new relationships.

The vehicle was assumed to be of height h, width 1.5h and length 9h. This gave a total surface area of 50h2. This was kept constant as the relative thickness of each side was altered. The base thickness is the weight factor for the armour factor carried. Thus, the set of relationships used are:

Facing Thickness
Front 3xbase
Sides 1.4xbase
Rear 0.4xbase
Top 0.6xbase
Bottom 0.6xbase

Example:
A vehicle with armour 40 would have 52 on the front, 43 on the sides, 29 on the rear and 33 on the top and bottom.

What I find interesting about this is that if you apply this to the Trepida it gives you a frontal armor rating that can withstand (just barely) a direct hit from a Z-80 main gun.

As to the weak sensors, I would say it implies the Trepida is designed to operate as part of a much larger combat force and rely on data links from higher command to track enemy forces outside its immidiate tactical circumstances (at least that's the hand wave I would use to explain it).

 

[Major B]

Example:
A vehicle with armour 40 would have 52 on the front, 43 on the sides, 29 on the rear and 33 on the top and bottom.

What I find interesting about this is that if you apply this to the Trepida it gives you a frontal armor rating that can withstand (just barely) a direct hit from a Z-80 main gun.

And it can withstand the A-series plasma guns too. That armor value rule is very elegant. I'd probably adjust the armor value a little higher for the bottom on grav vehicles and have to subtract a bit from somewhere else, but the idea is great one; easy to implement, adds detail without over-complication, and adds a requirement for some tactical thought.

As to the weak sensors, I would say it implies the Trepida is designed to operate as part of a much larger combat force and rely on data links from higher command to track enemy forces outside its immidiate tactical circumstances (at least that's the hand wave I would use to explain it).

That is the same explaination that I had in the back of my mind, but the inadequate communications array still makes that problematic for me. Some more powerful maser comm units would make that a viable option, and they're cheaper than adding sensors at KCr 10 for a 50km set.

 

[Major B]

Ranger, I'm trying to recreate your results on other vehicles for comparison and I'm missing something.

What is the number you are using as "base"?

 

[Ranger]

Well, its not actually mine, I just copied it off the web a few years ago (don't want to take credit for someone elses work). To be honest, I am just assuming his ratios equal up to the total volume for armor.

The way I've used it was to go to Table 9 on pg 43 of the Ref's Manual to convert the armor ratings to actual thickness, then back to armor ratings.

So, if you start with an Armor rating of 40, that becomes a Mod of 33 and you use that as the base. So for the front Armor, you take 33 x 3, which give you 99. go down the Mod column until you get to that Mod level without going over, and it gives you the new Armor Rating. In this case you have 95.1 (the next line is 104). The Armor Rating for that line is 52. Just keep doing the same for each of the various facings.

Does that make sense?

 

[Major B]

Does that make sense?

Yes. Thanks for the clarification and thanks to Stuart for the latest house rule to add to my files.

 

[Ranger]

I figured you would find it useful in your project. I found it because I was trying to retrofit some of the vehicles to Striker without completely redesigning them. BTW, if you think the Trepida is a mess, wait till you start working on the Astrin.

Considering there are a couple of other Imperial tanks that are much better over all, I would say the way to look at the Trepida is as part of an larger equipment package which includes the Astrin and the dismounted infantry it carries. If you take a 4 vehicle package, and give it 2 Trepidas and 2 Astrins (which carry 2 dismounted squads), then the Trepida makes a little more sense as a sort of "infantry tank." No anti-infantry weapons because the infantry in the Astrins provide security against other infantry. The Trepidas provide the local anti-armor combat power, the Astrins provide the speed for the infantry, and the infantry provide the anti-infantry combat power.

Just a thinking out loud.

 

[aramis]

Don't forget: Trepidas are able to operate surface to orbit... they are far more akin to AH64's than to M1A3's in terms of combat mission types. They don't NEED anti-infantry... they provide cover in mixed units (probably at a Bn level: Co A 3 Plt Inf, Co B & C 3 Plt Astrin, Co D 2 Plt Trepida, 1 Plt Astrin Special Assets {EW, Medic, Command, recovery}.)

In pure grav-armor, they are slow aircraft... Faster than helos, more nimble than many fixed wing, more powerful than either... but boy howdy, expensive. Against dangerous infantry, they disengage... by altitude. Against most infantry, they overkill.

 

[Major B]

Ranger and Aramis, I've been thinking along the lines of what types of vehicles with what capabilities I'd need to make to cover the weaknesses of the Trepida as shown, so I guess we're all thinking along the same lines.

And, I'll also pile on to aramis' post - grav vehicles have more in common with today's attack helos than they do with today's MBTs.

You're all making a strong case and leading me to believe that my initial impressions were a bit too harsh. Other than the actual errors in the published UCP, the design is not broken but it does have weaknesses. I think that the Trepida that ends up IMTU will have the VRFGG mounted coaxially to the main gun and will have a better commo suite, but no more.

And Ranger, your warning about the Astrin actually frightens me a little, because that was my next target vehicle, to be followed by the Empress.

Is there an interest in seeing a redone Trepida, to fix the errors and expand the UCP similar to what I did for the cavalry vehicle designs I've posted in the file library? If not, I'll just keep it for MTU, other than to post the errata changes for Don's compendium.

 

[aramis]

I only really used the Trepida and Astrin as color, really... but if you do it, it's worth sharing anyway.

 

[Ranger]

Well, the issue with the Astrin is that it's listed as 10 tons, but it has the same damage capacity as the Trepida, and its supposed to have the same volume as the Trepida (10 tons + 30%) as well. Plus it has a hard point, but no weapon system (which seems odd to me).

 

[Major B]

More on armor facings

Today I came back to look again at the armor facings rule by Stuart Machin (posted kindly by Ranger). I took a closer look so I could draft it into my growing house rules compendium and found a couple of problems.

I thought I'd post the problems and my solution here fr two reasons - to get fresh eyes on to check my work and (if correct) get the solution out where others might use it.

Stuart's model for determining the facing multipliers assumed a vehicle with height h, width 1.5 x h, and length 9 x h, producing a surface area of 50h2. Two problems with this that I see: Those dimensions produced a surface area of 48h2 when I did the math and a length of 9h seemed excessive to me.

For surface area, I assumed h = 1m so (1.5 + 1.5 + 9 + 9 + 13.5 + 13.5) = 48 m2

Second, rough comparisons of data for the M4, Pz V, M60, T72, M1, and T90 gave width values that ranged between (.95 x h) and (1.7 x h). The trend increased as designs modernized so Stuart's 1.5 figure seems reasonable, but length was off significantly. The range I found progressed from (2.13 x h) to (3.25 x h) so I used a length of (3 x h).

The results are not far off Stuart's marks. Retaining the 3x modifier for the front facing, 1.4 for the sides, .6 for the top, and .4 for the rear facing means the only change required is to reduce the bottom facing multiplier from .6 to .4.

 

[aramis]

1x1.6x9 is 50.