HG 2e Double Hull & Hamster Cage Cost and a couple of other questions

[snrdg121408]

Evening PDT all,

Question 1.

Double Hull: HG 2e pp. 10 & 12
This is a two-hulled cylinder where the outer hull (the whole, or at least a part) spins to create gravity and the inner hull does not. The outer hull is kept at around 1G by the speed of its spinning and is used for any areas that will be inhabited for extended periods of time, such as crew quarters. The outer, spun hull must be at least 60 tons. Machinery to spin a double hull uses 0.1 ton for every ton of outer hull. For each full percent of the total hull which is made part of the spun hull, the cost of the hull must be increased by +1%.

Hamster Cage: HG 2e p. 12
This is a series of spun rings set at right angles to the rest of the hull. The rings must have a radius of at least 15 metres in order to produce a gravitational field. Machinery to spin a hamster cage uses 0.1 tons for every ton of spun ring. Unlike other designs,
the hamster cage is usually set at right angles to the hull and installed in counter-rotating pairs, eliminating torque effects on the ship’s attitude. For each full percent of the hull which is made part of the hamster cage, the cost of the hull must be increased by +2%.

I've checked through a number of topics to verify how to calculate the increased hull cost when using a double hull or hamster cage and as usual my efforts failed.

To keep this simple, or I hope this is simple, a standard ship of 100 d-ton is built as a double hull at a cost of MCr5. Per the rules the minimum size of the out hull is 60 d-tons. The outer hull is 60% of the hull which means the hull cost is increased by 60%. The hull cost increase is MCr5 x 0.6 = MCr3 or MCr5 x 1.6 = MCr8.

A 60 meter hamster cage, yeah probably not a good idea but this way I only change the percentage, cost for the same hull is going to be 60% x 2% = 120%. The cost is MCr5 x 2.2 = MCr11.

Do I have the calculation correct to determine the cost?

Question 2:
What configurations can double hulls and hamster cage use?

 

[AnotherDilbert]

We had a similar conversation around here:
http://forum.mongoosepublishing.com/viewtopic.php?p=907886#p907886

Thank you for your help and I appear to be having a comprehension problem and or trying to eccentrically interpret the rules. I will try another route to see if I can get on the right track.

You're right, but I think you overcomplicate slightly.

I would say:
1. Choose total volume (exterior volume). Most further calculations are based on this, e.g. drives.
2. Choose Type: Gravity or Non-gravity.
3. Choose Configuration: Standard, Streamlined, Planetoid, etc.
4. Choose Special Features: Double Hull, Hamster Cage, and/or Breakaway Hull.

The cost becomes easy to calculate:
A 1000 dT hull, gravity, standard, 20% Hamster Cage costs 1000 × kCr 50 × 1.0 × ( 1 + 2% × 20 ) = MCr 70

A 1000 dT hull, non-gravity, streamlined, no special features costs 1000 × kCr 25 × 1.2 = MCr 30

A 1000 dT hull, gravity, planetoid, 20% Hamster Cage costs 1000 × kCr4 × ( 1 + 2% × 20 ) = MCr 5.6 (and has 800 dT usable space).

The only problem is if you chose type Non-gravity and configuration planetoid, because we do not know what that would cost.

 

[snrdg121408]

Morning PDT AnotherDilbert

We had a similar conversation around here:
http://forum.mongoosepublishing.com/viewtopic.php?p=907886#p907886

Thank you for your help and I appear to be having a comprehension problem and or trying to eccentrically interpret the rules. I will try another route to see if I can get on the right track.

You're right, but I think you overcomplicate slightly.

I would say:
1. Choose total volume (exterior volume). Most further calculations are based on this, e.g. drives.
2. Choose Type: Gravity or Non-gravity.
3. Choose Configuration: Standard, Streamlined, Planetoid, etc.
4. Choose Special Features: Double Hull, Hamster Cage, and/or Breakaway Hull.

The cost becomes easy to calculate:
A 1000 dT hull, gravity, standard, 20% Hamster Cage costs 1000 × kCr 50 × 1.0 × ( 1 + 2% × 20 ) = MCr 70

A 1000 dT hull, non-gravity, streamlined, no special features costs 1000 × kCr 25 × 1.2 = MCr 30

A 1000 dT hull, gravity, planetoid, 20% Hamster Cage costs 1000 × kCr4 × ( 1 + 2% × 20 ) = MCr 5.6 (and has 800 dT usable space).

The only problem is if you chose type Non-gravity and configuration planetoid, because we do not know what that would cost.

I knew I had asked the question before but as indicated my efforts to locate the material failed. Thank-you again since I do appear, in a round about fashion, to have the math correct.

I have another related question:
Per the rules the minimum radius of a hamster cage is 15 m to develop a gravitational field.

How much gravity does a hamster cage with a radius of 15 m generate?

How much gravity does a hamster cage with a radius of 30 m generate?

 

[Condottiere]

Wouldn't that depend on the rotational speed?

Which presumably is adjustable.

 

[snrdg121408]

Morning PDT Condottiere,

Wouldn't that depend on the rotational speed?

Which presumably is adjustable.

Hopefully, someone will explain why the minimum radius is 15 m, how the radius and whatever else determines the gravitational field on those in the hamster cage.

 

[AnotherDilbert]

In a hamster wheel the simulated gravity is not straight down, but curved away from the rotation. If the wheel is large the effect is not too bad.

https://en.wikipedia.org/wiki/Coriolis_force

 

[phavoc]

As an aside, this video has some good shots of the B5 Omega-class destroyer that has the rotating habitat.

https://www.youtube.com/watch?v=t3eSXfhL9AA

 

[snrdg121408]

Morning PDT AnotherDilbert and phavoc,

In a hamster wheel the simulated gravity is not straight down, but curved away from the rotation. If the wheel is large the effect is not too bad.

https://en.wikipedia.org/wiki/Coriolis_force

As an aside, this video has some good shots of the B5 Omega-class destroyer that has the rotating habitat.

https://www.youtube.com/watch?v=t3eSXfhL9AA

Thank you for the two links in an effort to answer my question or questions on a hamster cage hull.

My image of an hamster cage hull appears once again not to be the same as the rest of the Traveller community.

I've checked Chapter 11 Environmental Gravity section on p. 78 of TNE FF&S Mk I Mod 0 to compare the description of a hamster cage with the details i MgT HG 2e p. 13 and then searched the Internet for images that I believe supported my image based on the details in the two source books.

TNE FF&S Mk I Mod 1 p. 78
Hamster Cage: The hamster cage consists of a cylindrical module that is at 13 meters in radius, and that spins to create artificial gravity. Unlike other designs, the hamster cage is often set at right angles to the axis of the ship and generally installed in counter-rotating pairs (to eliminate torque effects on the ship's attitude).

Any ship hull form may use hamster cages, but the ship may not have an airframe configuration.

MgT HG 2e p. 12
Hamster Cage: This is a series of spun rings set at right angles to the rest of the hull. The rings must have a radius of at least 15 metres in order to produce a gravitational field. Machinery to spin a hamster cage uses 0.1 tons for every ton of spun ring. Unlike other designs, the hamster cage is usually set at right angles to the hull and installed in counter-rotating pairs, eliminating torque effects on the ship’s attitude. For each full percent of the hull which is made part of the hamster cage, the cost of the hull must be increased by +2%.

Based on the descriptions my image is pairs of rings that are mounted at right angles one on the left side or top and the other on the right side or bottom of the hull rotating in different directions.

Using Firefox my search criteria of space habitats yielded a link of Space Habitats Image results linked to Yahoo. Looking at the images I found one that I feel fits the MgT/TNE description. The image is on lifeboat.com, https://lifeboat.com/ex/space.habitats and titled Ark I.

The link to the B5 destroyer I'm guessing is an example of a double hull. In one of the science fiction books there is a description of what I think would be the spin capsule on TNE FF&S Mk I Mod 1 p. 78. I think the description was in the first or second book of the Star Carrier series by Ian Douglas.

From the link provided by AnotherDilbert and the MgT/TNE descriptions/requirements for a hamster cage the radius of 15 m/13 m coupled with the spin machinery's rotational speed is set at will determine the gravity felt inside the cage. My guess is that the minimum radius in both sources results in a 1G field.

The answer to my question of what happens when the cage's radius is increased appears to be nothing since the displacement tonnage is what determines the size of the spin machinery and that the cage is designed to rotate creating a 1G field for those characters from the Solomani home world. I guessing that if the Zhodani used a hamster cage then the rotation would simulate the gravity field of their home world.

So am I on the right page or in a totally different book?

 

[AnotherDilbert]

Based on the descriptions my image is pairs of rings that are mounted at right angles one on the left side or top and the other on the right side or bottom of the hull rotating in different directions.

Simpler would be something like:
http://canonicalmomentum.tumblr.com/post/149336128097/designing-a-spaceship-with-spin-gravity-part-1
Seen from the side:

A double hull would be something like this:

 

[snrdg121408]

Hello AnotherDilbert,

Thank you for the links and images. The first link and image is indeed a simpler version of what I image to be a hamster cage. I did not say that the Ark-I design was simple just that the the image has what my image of a hamster cage looks like.

A double hull would be something like this:

I do not agree that the image above represents a double hull based on the details from MgT 2e and TNE FF&S which are:

MgT HG 2e PDF pp. 10-11
"Double Hull: This is a two-hulled cylinder where the outer hull (the whole, or at least a part) spins to create gravity and the inner hull does not. The outer hull is kept at around 1G by the speed of its spinning and is used for any areas that will be inhabited for extended periods of time, such as crew quarters. The outer, spun hull must be at least 60 tons. Machinery to spin a double hull uses 0.1 ton for every ton of outer hull. For each full percent of the total hull which is made part of the spun hull, the cost of the hull must be increased by +1%."

TNE FF&S Mk 1 Mod 1 p. 78
"Double Hull: In this design, the outer hull spins but surrounds an enclosed inner hull which does not. Again, this design is most useful for very large ships as the enclosed central hull is at least 10 meters in radius.

Only cylinder hull form ships may use this type of spin habitat.

Double hulls require a volume of machinery equal to 1 % of the enclosed volume of the outer hull. Mass is 1 metric tonne per cubic meter and price is MCrO.OO1 per cubic meter."

Below is a static image of the B5 Omega-Class Destroyer which in the video link provided by phavoc has the section in the middle spinning. The middle section is what I feel meets the MgT HG 2e and TNE FF&S criteria for a double hull

 

[AnotherDilbert]

I would call that a "hamster cage", it's a spun habitat even if it is not a full ring.

A double hull implies a spun cylinder mostly enclosing the non-spun core.

 

[snrdg121408]

Hello AnotherDilbert,

I would call that a "hamster cage", it's a spun habitat even if it is not a full ring.

A double hull implies a spun cylinder mostly enclosing the non-spun core.

The image shown on the post with the time stamp Mon Mar 20, 2017 5:17 pm does not clearly show that the larger cylinder is enclosing the smaller cylinder. Further, the static image does not clearly convince me that the smaller cylinder is the non-spun core. What I see is that the smaller cylinder is attached to the larger cylinder.

The static image from the linked site of Canonical Momentum used in the post mentioned earlier shown below and we agree appears to be a hamster cage.

From the images on the site's pages they clearly meet the MgT criteria "The rings must have a radius of at least 15 metres in order to produce a gravitational field. Machinery to spin a hamster cage uses 0.1 tons for every ton of spun ring. Unlike other designs, the hamster cage is usually set at right angles to the hull and installed in counter-rotating pairs, eliminating torque effects on the ship’s attitude".

The B5 Omega-Class Destroyer video clip shows that the entire middle section is spinning in one direction. Looking at destroyer's video and image appears to show that the middle section to be two cylinders. The smaller inner cylinder appears not to be spinning while connecting the forward and aft hull sections, with the larger cylinder with the attached modules in the video clearly spins around the non-spinning smaller cylinder. Based on the material provided the destroyer does not meet the MgT criteria for hamster cage criteria or the breakaway hull.

 

[Condottiere]

Each floor could have a different gravity.

All I remember from my days at the roundabout is that you get propelled outwards.

 

[snrdg121408]

Hello again Condottiere,

Each floor could have a different gravity.

All I remember from my days at the roundabout is that you get propelled outwards.

From the science fiction stories I've read that used a similar system the IIRC inside of the outer hull is where the gravity is highest and heading to the other side the gravity weakens. Of course I may have the whole thing backwards or be totally wrong.

 

[phavoc]

Hello again Condottiere,

Each floor could have a different gravity.

All I remember from my days at the roundabout is that you get propelled outwards.

From the science fiction stories I've read that used a similar system the IIRC inside of the outer hull is where the gravity is highest and heading to the other side the gravity weakens. Of course I may have the whole thing backwards or be totally wrong.

Nope, that's accurate. With spin you could provide different levels of gravity at different distances from the core.

 

[snrdg121408]

Hello phavoc,

Hello again Condottiere,

Each floor could have a different gravity.

All I remember from my days at the roundabout is that you get propelled outwards.

From the science fiction stories I've read that used a similar system the IIRC inside of the outer hull is where the gravity is highest and heading to the other side the gravity weakens. Of course I may have the whole thing backwards or be totally wrong.

Nope, that's accurate. With spin you could provide different levels of gravity at different distances from the core.

Yippee, I did recall the information correctly and thank you for the confirmation. Now if I can keep the momentum I may be able to get a handle on other items.

 

[snrdg121408]

Morning PDT,

The image shown below looks more like an O'Neil cylinder space habitat to me.

The MgT Double Hull and Hamster Cage are technically habitats that have been modified by adding full maneuver drives rather than station keeping thrusters.

 

[vladthemad]

I'll try to make it easy to understand, as it took me awhile to get some of the science behind it, but it's easy to get when it's in layman's terms. You may have figured a lot of it out as a kid actually.

If you hold a bucket of water and spin around real fast, the bucket can hang out at a right angle to gravity but the water will stay in the bucket. In this example, the bucket...well actually the circular arc the bucket travels through in the case of a torus/hamster cage...is the spin habitat and you are the ship.

To make this easier to understand, let's use a giant spinning the bucket with you and some friends standing inside the bucket. If the giant puts a rope on the bucket to get it further away from him while spinning, you'll find that he doesn't have to spin it as fast to keep you held to the bottom of the bucket. This is why larger spin habitats spin slower. Correspondingly, if the giant pulls the bucket in closer he will have to spin much faster to keep up the same effect. The giant is the ship, and the bottom of the bucket is the floor of the spin habitat.

Now the Coriolis effect is where it gets tricky. Lets say the giant wanted to throw a small ball to you in that bucket while you were spinning. If he throws it straight out aiming for the bucket, by the time the ball gets to where he was aiming, the bucket will have moved because he's still spinning it and he'll miss. Now imagine trying to throw a ball to your friend that is in the bucket with you. The same effect that caused the giant to miss will play all sorts of havoc when you try to throw the ball to your friend. Once that ball leaves your hand, it's no longer affected by the spinning action that keeps your feet held to the bottom of the bucket. It's going to travel in a straight line in the direction you threw it, but the bucket is NOT travelling in a straight line. What the ball does depends on which direction you threw it, but needless to say it's not going where you intended. On top of that, this also effects YOU. Your head is closer to the giant than your feet are. As such, you will almost always feel like you are falling because your feet will be travelling around faster than your head. It will feel like your feet are constantly moving out from under you. The faster the giant has to spin the bucket, the more of this you will feel. So you want to make sure that the giant puts the bucket at the end of a really long rope...or you have the spin habitat a minimum distance away from the center line of the ship to minimize this feeling and keep you from falling to the floor all the time.

Now, in general, a hamster wheel configuration is as many have pictured. The spin habitat is out at the end of long pylons with a needle like ship in the center. The double hull concept isn't the same as with a submarine. Submarines are using two hulls for very different reasons! To help imagine how a double hull spin habitat works, think of two red solo cups stacked together. Hold the inside cup (the ship) and spin the outside cup (the spin habitat) and you'll understand what they mean.

Hopefully that helped more than it confused!