Terran Commonwealth -- Book 2 Starship Combat

[tbeard1999]

One thing to remember is that a starship in combat is usually under thrust, which means that its structure is under constant stress by the acceleration (unless you're using a totally inertialess drive, that is). If the ship's main structure is hit too badly but the engine keeps running, it might collapse under this stress...

CT drives are reactionless, but not inertialess. And given that ships with 6G acceleration are possible, and can accelerate for a LONG time, CT has to have some kind of compensation system for the crew. A human couldn't stand 6G acceleration without permanent injury for more than 5 minutes or so (maybe 10 minutes if immersed in a fluid), so some kind of handwavium device must protect the crew. In a military starship, there'd be serious redundancy for such a system. But a critical hit on this system could cause a combat starship serious difficulty. In my campaign, I assume it's part of the gravitics system. If the gravitics are knocked out, the ship is limited to 1G sustained acceleration.

But I don't think that lasers and even shaped-charge high explosive missiles will cause the kind of structural damage that would compromise a ship's ability to maneuver at high acceleration.

--Ty

 

[aramis]

Ty: you numbers for 6G are off by about an order of magnitude; combat fighter pilots sustain 5+G's for half an hour+, and have since WWII.

I do agree that compensation is required.

Cap'nJack: Hydrogen and Oxygen combine incredibly cleanly, don't autoignite, and won't burn visibly ouside atmospheres.

 

[captainjack]

Ty: you numbers for 6G are off by about an order of magnitude; combat fighter pilots sustain 5+G's for half an hour+, and have since WWII.

I do agree that compensation is required.

Cap'nJack: Hydrogen and Oxygen combine incredibly cleanly, don't autoignite, and won't burn visibly ouside atmospheres.

Yes, that was my argument, and you'd think both chemistry and being the GM could carry the point, but no........they had to have their smoke trail.

One thought, though- the main risk from a fuel hit that vented internally probably wouldn't be flames, but rather cryogenic liquid spewing everywhere....possibly with an expansion explosion if it was a high enough energy hit (laser, say..) to suddenly vaporize some of the hydrogen. Messy.

cap

 

[tbeard1999]

Ty: you numbers for 6G are off by about an order of magnitude; combat fighter pilots sustain 5+G's for half an hour+, and have since WWII.

I do agree that compensation is required.

Cap'nJack: Hydrogen and Oxygen combine incredibly cleanly, don't autoignite, and won't burn visibly ouside atmospheres.

4-6G acceleration for more than a few seconds is sufficient to induce blackout. G suits mitigate this to some degree, but fighter pilots (who are in excellent physcial condition, belted into a sitting position, and trained to endure high acceleration) still can't endure high acceleration for more than a few seconds without blacking out. Of course, a typical aircraft maneuver won't last more than a few seconds. Very few modern fighters can accelerate greater than 1G (the F-15 is one) and even they can't exceed 1G for long (fuel is the limited) or by very much. Maneuvers are the way that modern aircraft can dramatically exceed 1G and I can't imagine any conceivable series of maneuvers that could constantly stress the pilot for 30+ minutes.

According to an article on Aerospace Medicine "f a force of 4 to 6g is sustained for more than a few seconds, the resulting symptoms range from blackouts to total death..."

The eyes, bladder (especially if full), and heart are particularly vulnerable to high acceleration.

Of course, it requires extremely high acceleration levels to *instantaneously* kill a human being -- 70G or so.

--Ty

 

[aramis]

Sorry Ty, but Science disagrees.

Time (min)      +Gx     -Gx     +Gz      -Gz
.01 (<1 sec)     35      28      18        8
.03 (2 sec)      28      22      14        7
.1               20      17      11        5
.3               15      12       9        4.5
1                11       9       7        3.3
3                 9       8       6        2.5
10                6       5       4.5      2
30                4.5     4       3.5      1.8

"Bioastronautics Data Book,", NASA SP-3006, 1964
titled "G Tolerance in 4 vectors". It is unfortunately not clear if
"tolerance" means before blackout, or before some other limit; also, it
is not clear if this includes the use of G-suits, etc. Since the
plot is included in a design study for a high-acceleration vehicle, I
think it is safe to assume these are roughly what NASA considers safe for
manned vehicles

Kare cites Paul Webb, MD, from NASA SP-3006 (1964).

The second edition notes on page 151 give a +Gx of restrcition of vision in the +3-+6 G range. The above table is a snapshot from the table on page 173. 6G looks to be about 7 minutes

Vertical G's are intolerable after a few seconds; The apollo astronats suffered 6+ frontal G's for several minutes; Voluntary times for "highly motivated test pilots" range to 500 seconds (8 1/3 minutes); the data adjustments for protections are listed on p177; this implies the prior tables are uncompensated.

 

[whartung]

You guys can quote minutes all day long, but last I checked most ship-to-ship game turns are measured in 20 minutes to 1/2hr. That implies 20-30 minutes of sustained acceleration.

Right now, one of the problems facing Indy car drivers is the G's pulled in the corners at the oval tracks. The problem is simply blood pooling on one side (right side) of the body during the race. There simply isn't enough time in the straights for the blood to recover, so the racers are facing human limits in how fast the cars can run the track (they're doing today, what, 220+ MPH now??). Now they pull I think 2-3+ G's in those corners, and none of this happens instantaneously, but they only run for about 1/2 hr between pits stops (if that), and these limitations are coming in to play.

Now, astronauts suffer hard G's, mostly during reentry as I understand it, but beyond talking they're not particularly functional and, again, it's simply not that long.

Now, not to debate NASA scientists, but it's fair to argue that there's a difference between highly trained astronauts and the riff raff that mans the engineering spaces of a combat ship in Traveller.

TNE uses the artifical grav system as a compensation system for ships.

Regarding the arms/density issue in B2, the issue is simply that fighters let spare space be converted into firepower, however inefficiently. The fact that spare space can be converted at all is important. Even inefficient firepower is better than no firepower.


Bays are interesting only in that they route around the 1 hardpoint/100 dtons rule, but if you end up with excess volume, you're still behind the curve.

Surface area (and internal tonnage of course) is a better limiting factor for surface mounted weapons -- then the goal is to design the ship with the greatest surface area to volume ratio, so that there is not wasted volume. If there is wasted volume, then it can be filled with fighters and the debate continues.

 

[tbeard1999]

Sorry Ty, but Science disagrees.

With whom? You claimed that "...combat fighter pilots sustain 5+G's for half an hour+, and have since WWII." What, in the table below, supports that contention?

Time (min)      +Gx     -Gx     +Gz      -Gz
.01 (<1 sec)     35      28      18        8
.03 (2 sec)      28      22      14        7
.1               20      17      11        5
.3               15      12       9        4.5
1                11       9       7        3.3
3                 9       8       6        2.5
10                6       5       4.5      2
30                4.5     4       3.5      1.8

Kare cites Paul Webb, MD, from NASA SP-3006 (1964).

The second edition notes on page 151 give a +Gx of restrcition of vision in the +3-+6 G range. The above table is a snapshot from the table on page 173. 6G looks to be about 7 minutes

Vertical G's are intolerable after a few seconds; The apollo astronats suffered 6+ frontal G's for several minutes; Voluntary times for "highly motivated test pilots" range to 500 seconds (8 1/3 minutes); the data adjustments for protections are listed on p177; this implies the prior tables are uncompensated.

Is there a link to this data? You do not appear to have explained what the various entries on the table mean.

In any case, if your point is that humans can survive for a few minutes at high Gs, then I'm not interested in further dissection. However, you claimed that human fighter pilots routinely withstood 5-Gs for "half an hour+". *That* is the contention that my sources seem to dispute and what I'm interested in.

--Ty

 

[tbeard1999]

You guys can quote minutes all day long, but last I checked most ship-to-ship game turns are measured in 20 minutes to 1/2hr. That implies 20-30 minutes of sustained acceleration.

We must have been unclear, but we get that. We've both agreed that humans cannot handle long term exposure to high-G acceleration. So, we agree with you that high-G acceleration would be intolerable to humans in games with game turns representing 20-30 minutes.

What were doing now is trying to discern the lower limits. Aramis says about 1/2 hour, my sources say far less.

Regarding the arms/density issue in B2, the issue is simply that fighters let spare space be converted into firepower, however inefficiently. The fact that spare space can be converted at all is important. Even inefficient firepower is better than no firepower.

A more important point (to my assertion, at least) is that fighters are the ONLY way to allocate tonnage to weaponry (other than the inconsequential 1 ton of fire control per turret). That is unacceptable for my campaigns, which envision a WWI-WWII style naval environment in which carriers and "surface ships" are both viable.

Surface area (and internal tonnage of course) is a better limiting factor for surface mounted weapons -- then the goal is to design the ship with the greatest surface area to volume ratio, so that there is not wasted volume. If there is wasted volume, then it can be filled with fighters and the debate continues.

I agree, but Book 2 does not have a surface area mechanism. While I could assume a certain surface area for X tons, I wanted a mechanic that would be compatible with existing Book 2 ship designs. So I stayed with the High Guard bay weapons concept to avoid re-figuring the existing Book 2 ships.

--Ty

 

[aramis]

With whom? You claimed that "...combat fighter pilots sustain 5+G's for half an hour+, and have since WWII." What, in the table below, supports that contention?



Is there a link to this data? You do not appear to have explained what the various entries on the table mean.

In any case, if your point is that humans can survive for a few minutes at high Gs, then I'm not interested in further dissection. However, you claimed that human fighter pilots routinely withstood 5-Gs for "half an hour+". *That* is the contention that my sources seem to dispute and what I'm interested in.

--Ty

Go to NASA, and search for the document. It goes into all kinds of gory details. Here's a link to page 177:
http://articles.adsabs.harvard.edu//full/1973NASSP3006.....P/0000187.000.html

bandages applied to legs and abdomen can protect against up to 0.8G...
Full pressure suits protect up to 1.4G, putting sustained 6G at 4.6G effect. Since 30m has a threshold for +Gx of 4.5g's, a TL 6 G-suit (the old Clark model) should enable about 30 minutes at 6G along a front-to-back accelleration, and should result in much reduced visual field (45° or so)... and even so, the 5m exposures you mention do not result in "Permanent" damage, just loss of useful consiousness.

Now, even a 2G artificial gravity compensation puts a flight-suit compensation assist into the several hours range...

By the way, to explain how to read the table posted earlier: left column is time. entries in other columns are uncompensated G's sustainable for that time, and the other tables imply this to be useful consciousness.

 

[captainjack]

Ty said this.
"A human couldn't stand 6G acceleration without permanent injury for more than 5 minutes or so (maybe 10 minutes if immersed in a fluid),"

Aramis table reads thus:
Time (min) +Gx -Gx +Gz -Gz
<snip>
10 6 5 4.5 2
30 4.5 4 3.5 1.8

Note that at ten minutes, the table says 6g ? Okay, so perhaps they weren't immersed in fluid - although the difference functionally between that and secured in a hi-G centrifuge seat escapes me. He's right about the G limit time, you're right about the level of support. Okay ?

Stop writing your names in the snow, and get back in the classroom.

Questions for discussion: Near-c rocks, jump masking and stellar type generation.

Cap

 

[tbeard1999]

Go to NASA, and search for the document. It goes into all kinds of gory details. Here's a link to page 177:
http://articles.adsabs.harvard.edu//full/1973NASSP3006.....P/0000187.000.html

bandages applied to legs and abdomen can protect against up to 0.8G...
Full pressure suits protect up to 1.4G, putting sustained 6G at 4.6G effect. Since 30m has a threshold for +Gx of 4.5g's, a TL 6 G-suit (the old Clark model) should enable about 30 minutes at 6G along a front-to-back accelleration, and should result in much reduced visual field (45° or so)... and even so, the 5m exposures you mention do not result in "Permanent" damage, just loss of useful consiousness.

Now, even a 2G artificial gravity compensation puts a flight-suit compensation assist into the several hours range...

By the way, to explain how to read the table posted earlier: left column is time. entries in other columns are uncompensated G's sustainable for that time, and the other tables imply this to be useful consciousness.

Note the chart on page 186 (the page just before your cite): http://articles.adsabs.harvard.edu//full/1973NASSP3006.....P/0000186.000.html

The first diagram (4-29) yields the following durations for 6-G:
15 minutes for immersion in water
<5 minutes for all other postures.

This is the "tolerance" limit, whatever that is.

Page 174 has a graph showing that "highly motivated test pilots" had a "voluntary endurance" at 6G of ~180 seconds to ~540 seconds depending on acceleration angle.

Figure 4-25 shows a maximum tolerance of 10 minutes at 6G and a minimum tolerance of .05 minutes.

In any case, I still see no evidence that pilots routinely experience 5+G acceleration for periods of ~30 minutes.

--Ty

 

[tbeard1999]

Stop writing your names in the snow, and get back in the classroom.
Cap

Good idea. Wish I'd read this post before replying. In any case, we appear to agree on my main point, which is that CT starship will require some kind of handwavium compensators to protect humans from sustained high-G acceleration.

I don't think I actually care for further quibbling over what the exact number of minutes is (although I maintain that that number -- whatever it is -- is significantly less than 30 minutes in any reasonable scenario).

 

[Bob Weaver]

tbeard,
Permit me to try again. If I understand you correctly, what you were looking for at the start of this thread was a way by which you could improve the firepower of a 'battleship' type craft in a way that was unavailable to a 'carrier' type craft. Bk2 as written is nowhere near that detailed, and as you've pointed out, by strait Bk2 rules, the carrier is a much more firepower-efficient platform. My previous posts downgraded the carrier rather than upgrading the battleship.
Looking at history, why didn't WWII carriers have massive firepower? Because of their design. The flat deck was needed to launch aircraft, so there was nowhere to put the big gun turrets. So what does that say about designing Bk2 carriers? Configuration rules? Or perhaps some other design rule that changes the '1 turret per 100 tons' rule when designing a carrier.
I'm afraid I don't have any good suggestions at the moment, but now at least I appreciate the problem you're addressing. I hope a solution can be found that works for you.

Best Regards,

Bob W.

 

[Bob Weaver]

Oh, I did it again. I forgot my other point. Have you considered armor rules, such that the space/tonnage required would make them impractical for the carrier? Then at least the DEVESTATION would be at an advantage over TITANIC. Identical guns, but DEV can shrug off some (most) of TITANIC's fire.

Best Regards,

Bob W.

 

[Golan2072]

Looking at history, why didn't WWII carriers have massive firepower? Because of their design. The flat deck was needed to launch aircraft, so there was nowhere to put the big gun turrets. So what does that say about designing Bk2 carriers? Configuration rules? Or perhaps some other design rule that changes the '1 turret per 100 tons' rule when designing a carrier.

One possibility is to make hangars (at least the quick-launch ones used by carriers) take hardpoints just like turrets; 2-5 craft per hardpoint would be a good idea. So you will have to choose between small craft and armament.

 

[aramis]

Or each launch door takes a hardpoint, and can launch 1 craft per turn.

 

[captainjack]

Or each launch door takes a hardpoint, and can launch 1 craft per turn.

No, I really am with Ty on this one. WWII carriers were the main battle units due to their ability to engage and destroy any other unit, and do it from a great (and safe )distance. That isn't the capability of traveller fighters as far as I've ever seen. A major factor in gun design, equal to armor pen, is range. Battleships can obliterate cruisers with almost no risk, not necc. because of their gun caliber ( a hit by a 12" gun is about as serious as a hit from an 18" gun, insofar as both turn the cruiser into an instant rising column of smoke and flames), but because they can stand off out of cruiser range and pummel at will - and with no hits incoming, accuracy is VASTLY increased to boot. For reference, the last stand of the German pacific squadron in WWI.

The problem is this: with only turrets/hardpoints, merchants can have the same damage inflicting and stand-off capacity as battleships. The situation isn't even analogous to the Naploeonic age of sail - it is MUCH more like pre-armada fighting. Most warships were merchants, with land guns added. The development of the purpose built fighting ship is what destroyed the armada; smaller warships regularly defeated larger armed merchantmen. Also, the whole issue of armed merchants was quite contentions in the 1600's, as while they had decent numbers of guns on paper, they were invariably smaller than warship guns, and the ships were structurally weaker, and often a liability in combat due to their fragility. The fleet was regarded as much stronger once the merchantmen-o-war were left home.

Which is a VERY long winded, pedantic way of saying, yes: military ships need some way of converting hull capacity to weaponry other than turrets.

I use military turrets ("barbettes") in various sizes which take hardpoints, but also are more powerful, longer ranged, and require a much larger share of the ships volume (as opposed to 1dT for turrets) to include extra sensors, targeting, protection, and most of all, dedicated powerplants. (Using CT, thus no HG EP) With some smaller Bays for smaller than 1000dT ships, and armor rules, this seems to work, quite well.


-Cap

 

[tbeard1999]

Oh, I did it again. I forgot my other point. Have you considered armor rules, such that the space/tonnage required would make them impractical for the carrier? Then at least the DEVESTATION would be at an advantage over TITANIC. Identical guns, but DEV can shrug off some (most) of TITANIC's fire.

Best Regards,

Bob W.

I stayed away from armor for several reasons:

1. I'd have to add a new value to the hull chart -- surface area. This would be used to determine the tonnage of armor. I'd also have to write and test an armor mechanic. Not huge problems, but I wanted to change as few of the underlying rules as possible.

2. Armor rules would require me to add even more weapons. The natural response to effectice armor would be armor piercing weapons. So we'd have to have multiple sizes of lasers, etc. I'd then have to go back and revise the larger militaryt starships in book 2, something I wanted to avoid.

So while adding armor might accomplish my objectives, it looked to me to be a more time consuming process than simply adapting HG bay weapons for Book 2.

--Ty

 

[aramis]

Here's a way to handle armoring that doesn't "need" surface area:

Set max hull hits to, say 1 per 20 Tons. (this gives better than Mayday's 4 in 1 turn)
Allow each 5 tons of "Armor" to add 1 hull hit, and the hull doesn't depressurize until the additional hits are depleted.

Since it ignores surface area, and focuses on reducing damage effect of hull hits, and sets a cumulative damage effect on hull hits.

 

[Bob Weaver]

I stayed away from armor for several reasons:

1. I'd have to add a new value to the hull chart -- surface area. This would be used to determine the tonnage of armor. I'd also have to write and test an armor mechanic. Not huge problems, but I wanted to change as few of the underlying rules as possible.

2. Armor rules would require me to add even more weapons. The natural response to effective armor would be armor piercing weapons. So we'd have to have multiple sizes of lasers, etc. I'd then have to go back and revise the larger military starships in book 2, something I wanted to avoid.

So while adding armor might accomplish my objectives, it looked to me to be a more time consuming process than simply adapting HG bay weapons for Book 2.

--Ty

Ty,

It appears that no matter what route you take to bring parity to the 'battleship' model vis a vis the 'carrier' model, it's going to take some modification of the very simple ship design of Bk2. I'm not knocking Bk2 design, but it is not a very detailed system. Customization, whether built on physics or handwavium is unavoidable. I probably have a higher tolerance for handwavium than you do, based on your posts in this thread, but your TU is yours, so do what suits you best. I'm good with some simple armor rules and launch facilities that take up weapon space, but on the other hand, I'm not in favor of 1-place fighter craft. I prefer the SDB/gunboat model - I think they are more likely to survive combat and can be used by small PC groups.

Best Regards,

Bob W.