Ship Design Philosophy

[Condottiere]

Spaceships: Hulls, Planetoids and Breakaways

Since it's not explicitly forbidden, you have to wonder if planetoid configurations can be configured with breakaway sections.

Planetoids don't have to look like potatoes, they could be sculpted in Borg cubes; buffered planetoids with their advantages against meson bombardment would be a different issue, planetoids are just lumps of nickel iron that get cored out, and need twenty percent of shell to maintain structural integrity, I would assume, since you'll need some room for error, overcompensated to the point you get two factors of armour protection.

Take a large enough laser, and start slicing off sections, and then add two percent of clamps that will hold them together; true, you probably have to carefully design the interior so that at the connecting sections you have that twenty percent as buffer. Or you could take two lumps of nickel iron and shave the connecting areas to get a tight fit, then add the connecting clamps.

What are the advantages: beyond the basic five thousand schmucker per tonne for a gravitated hull, which is ten times cheaper than the default. The two percent for breakaway is net total, which means you could slice up a hull like salami, since it's not per, but a set overhead.

To a certain extent, making this about planetoids is more of a diversion, but the concept itself holds potential, and you have to set up the fact that a nicely salamied nickel iron hull can be added to another material, as long as the connecting clamps correspond.

 

[Old School]

Anything that has a cost based on a percentage of hull cost is going to be cheesy when applied to planetoids due to their low hull cost. Breakaway hulls and armor come to mind. You can conjure up a justification for the low cost if you like, but its still cheese.

 

[AnotherDilbert]

Anything that has a cost based on a percentage of hull cost is going to be cheesy when applied to planetoids due to their low hull cost. Breakaway hulls and armor come to mind.

No cheese with breakaway; cost isn't proportional to hull cost.

Low cost of armoured planetoids is intended, unfortunately.

Armour for planetoid hulls cost very little since the armour cost is based on hull cost. I guess that is not intended.

Think of it this way, you can hollow out less and use the planetoid for part of the armour. (Not that that actually covers the different armour types).

 

[AndrewW]

Anything that has a cost based on a percentage of hull cost is going to be cheesy when applied to planetoids due to their low hull cost. Breakaway hulls and armor come to mind.

No cheese with breakaway; cost isn't proportional to hull cost.

Low cost of armoured planetoids is intended, unfortunately.

Not really, just a consequence of using the existing system.

 

[Condottiere]

Armour plating should be by tonne, modified only in the quantity required by the type of hull configuration, spherical should be minimal.

For planetoids, quantity based on usable volume.

 

[Old School]

I can see a discount for certain shapes based on ease of construction, same as the hull, but you can put 14 points of bonded superdense armor on a planetoid really cheap. I could see it being cheaper than the others, but its too cheap. I’d probably use the same cost as armor for a sphere if it ever came up in my game.

 

[dragoner]

I found with 1e that the easiest way to fix the system was to eliminate armor, and just use the core rules. It was quick, easy, and logical; made combat faster.

 

[Condottiere]

Deflector screens and force fields require juice, probably a more logical calculation.

 

[dragoner]

The simpler solution would be to not have them; there are point defense and ECM as traditional trav systems.

 

[Condottiere]

Armour is a relatively cheap form of protection, which besides the cost and volume usage, would still be used by those who believe it is an effective solution against some or most forms of damage delivery.

 

[dragoner]

Armor, while it's unrealistic for a variety of reasons, and it seems that it's mostly represented as "material thickness" a design idea rendered obsolete by the British with their development of Chobham Armour; mostly it is passive. The main design philosophy focus should be how the player characters interact with the designs, and passivity is a poor choice, over something like taking M drive number, plus pilot skill, and comparing them to give a "parry bonus" to maneuvers to avoid getting hit. Then again, I have been playing a lot of M-Space currently in my face to face group. That passivity means it affects players, without them really being to interact with it, and in turn it sort of reduces the granularity of 2d6, which it sorely needs.

 

[Condottiere]

Tank design is a compromise of mobility, firepower and protection.

You can't outrun a missile or a cannon shell; you can try to see first, shoot first, hit first. Of course, if the enemy is moving around, and trying to do the same to you, that degrades accuracy. With modern ordnance, a direct hit should be fatal, but not necessarily for the crew, as protective measures, including a buffer of material thickness, using differing materials to deflect or mitigate various lethal effects.

That thickness could be the difference between life and death, or if hit at an angle, bounces off.

And of course, it's mosquito proof.

 

[dragoner]

Designing a spacecraft like a WW2 tank is weird. For material thickness, hitting a paint chip at orbital velocities and the resultant spalling sends fragments through the interior of the vehicle. Hit by a missile or beam, the material can explode into a cloud of plasma.

 

[Condottiere]

Tank construction and combat has been experienced, so we have a fair idea of what and what doesn't work.

Spaceship combat using a made up combat system and ship design system is pretty much hit and miss.

Tee Five allows composite armouring, and presumably a laser has a different effect from a nuclear missile.

All you can do is look at the damage tables and figure out the best way of protecting a specific ship design against the most likely threats.

 

[dragoner]

"Game the rules."
-Eurisko

:wink:

Space combat could be not so exciting ...

 

[Condottiere]

Speaking of Harrington, as I recall, you can see death coming if the other side launches enough missiles.

 

[Condottiere]

Inspiration: Astartes (Warhammer Forty Kay Fan Film)

https://www.youtube.com/watch?v=g-MteECxZUY
https://www.youtube.com/watch?v=mfGPMJ8A0QY
https://www.youtube.com/watch?v=CMGRa4_UjE4

Boarding action; plausible, if you can blast a hole through armour plating.

 

[phavoc]

Spaceships: Hulls and Heat Shields

There are four critical parameters considered when designing a vehicle for atmospheric entry:
Peak heat flux
Heat load
Peak deceleration
Peak dynamic pressure
Peak heat flux and dynamic pressure selects the TPS material. Heat load selects the thickness of the TPS material stack. Peak deceleration is of major importance for manned missions. The upper limit for manned return to Earth from low Earth orbit (LEO) or lunar return is 10g.[52] For Martian atmospheric entry after long exposure to zero gravity, the upper limit is 4g.[52] Peak dynamic pressure can also influence the selection of the outermost TPS material if spallation is an issue.
Starting from the principle of conservative design, the engineer typically considers two worst case trajectories, the undershoot and overshoot trajectories. The overshoot trajectory is typically defined as the shallowest allowable entry velocity angle prior to atmospheric skip-off. The overshoot trajectory has the highest heat load and sets the TPS thickness. The undershoot trajectory is defined by the steepest allowable trajectory. For manned missions the steepest entry angle is limited by the peak deceleration. The undershoot trajectory also has the highest peak heat flux and dynamic pressure. Consequently, the undershoot trajectory is the basis for selecting the TPS material. There is no "one size fits all" TPS material. A TPS material that is ideal for high heat flux may be too conductive (too dense) for a long duration heat load. A low density TPS material might lack the tensile strength to resist spallation if the dynamic pressure is too high. A TPS material can perform well for a specific peak heat flux, but fail catastrophically for the same peak heat flux if the wall pressure is significantly increased (this happened with NASA's R-4 test spacecraft).[52] Older TPS materials tend to be more labor-intensive and expensive to manufacture compared to modern materials. However, modern TPS materials often lack the flight history of the older materials (an important consideration for a risk-averse designer).
Based upon Allen and Eggers discovery, maximum aeroshell bluntness (maximum drag) yields minimum TPS mass. Maximum bluntness (minimum ballistic coefficient) also yields a minimal terminal velocity at maximum altitude (very important for Mars EDL, but detrimental for military RVs). However, there is an upper limit to bluntness imposed by aerodynamic stability considerations based upon shock wave detachment. A shock wave will remain attached to the tip of a sharp cone if the cone's half-angle is below a critical value. This critical half-angle can be estimated using perfect gas theory (this specific aerodynamic instability occurs below hypersonic speeds). For a nitrogen atmosphere (Earth or Titan), the maximum allowed half-angle is approximately 60°. For a carbon dioxide atmosphere (Mars or Venus), the maximum allowed half-angle is approximately 70°. After shock wave detachment, an entry vehicle must carry significantly more shocklayer gas around the leading edge stagnation point (the subsonic cap). Consequently, the aerodynamic center moves upstream thus causing aerodynamic instability. It is incorrect to reapply an aeroshell design intended for Titan entry (Huygens probe in a nitrogen atmosphere) for Mars entry (Beagle-2 in a carbon dioxide atmosphere).[citation needed][original research?] Prior to being abandoned, the Soviet Mars lander program achieved one successful landing (Mars 3), on the second of three entry attempts (the others were Mars 2 and Mars 6). The Soviet Mars landers were based upon a 60° half-angle aeroshell design.
A 45° half-angle sphere-cone is typically used for atmospheric probes (surface landing not intended) even though TPS mass is not minimized. The rationale for a 45° half-angle is to have either aerodynamic stability from entry-to-impact (the heat shield is not jettisoned) or a short-and-sharp heat pulse followed by prompt heat shield jettison. A 45° sphere-cone design was used with the DS/2 Mars impactor and Pioneer Venus Probes.

This is not an issue in the Traveller universe, or any other, so long as they have control over gravity. Assuming they are trying to make an entry into the atmosphere without their contragravity system working, then it would remain applicable, though materials would alter the calculations. All they would need to do is match the orbital rotation velocity and simply sink into the atmosphere. We cannot do that today, so you never see any calculations or discussions on it.

 

[Condottiere]

It was more relevant in the last edition, when rockets were smaller and cheaper, and I had a clear idea how high burn thrusters functioned.

I'm also slowly moving to more or less to one shot assault shuttles and/or drop pods.

 

[Condottiere]

Spaceships: Life Support and Carbon dioxide scrubber

Lithium hydroxide[edit]
Other strong bases such as soda lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide are able to remove carbon dioxide by chemically reacting with it. In particular, lithium hydroxide was used aboard spacecraft, such as in the Apollo program, to remove carbon dioxide from the atmosphere. It reacts with carbon dioxide to form lithium carbonate.[10] Recently lithium hydroxide absorbent technology has been adapted for use in anesthesia machines. Anesthesia machines which provide life support and inhaled agents during surgery typically employ a closed circuit necessitating the removal of carbon dioxide exhaled by the patient. Lithium hydroxide may offer some safety and convenience benefits over the older calcium based products.
2 LiOH(s) + 2 H2O(g) → 2 LiOH·H2O(s)
2 LiOH·H2O(s) + CO2(g) → Li2CO3(s) + 3 H2O(g)
The net reaction being:
2LiOH(s) + CO2(g) → Li2CO3(s) + H2O(g)
Lithium peroxide can also be used as it absorbs more CO2 per unit weight with the added advantage of releasing oxygen.[11]
Regenerative carbon dioxide removal system[edit]
The regenerative carbon dioxide removal system (RCRS) on the space shuttle orbiter used a two-bed system that provided continuous removal of carbon dioxide without expendable products. Regenerable systems allowed a shuttle mission a longer stay in space without having to replenish its sorbent canisters. Older lithium hydroxide (LiOH)-based systems, which are non-regenerable, were replaced by regenerable metal-oxide-based systems. A system based on metal oxide primarily consisted of a metal oxide sorbent canister and a regenerator assembly. It worked by removing carbon dioxide using a sorbent material and then regenerating the sorbent material. The metal-oxide sorbent canister was regenerated by pumping air at approximately 400 °F (204 °C) through it at a standard flow rate of 7.5 cu ft/min (0.0035 m3/s) for 10 hours.[12]
Activated carbon[edit]
Activated carbon can be used as a carbon dioxide scrubber. Air with high carbon dioxide content, such as air from fruit storage locations, can be blown through beds of activated carbon and the carbon dioxide will adsorb onto the activated carbon. Once the bed is saturated it must then be "regenerated" by blowing low carbon dioxide air, such as ambient air, through the bed. This will release the carbon dioxide from the bed, and it can then be used to scrub again, leaving the net amount of carbon dioxide in the air the same as when the process was started.
Metal-organic frameworks (MOFs)[edit]
Metal-organic frameworks are one of the most promising new technologies for carbon dioxide capture and sequestration via adsorption. Although no large-scale commercial technology exists nowadays, several research studies have indicated the great potential that MOFs have as a CO2 adsorbent. Its characteristics, such as pore structure and surface functions can be easily tuned to improve CO2 selectivity over other gases.[13]
A MOF could be specifically designed to act like a CO2 removal agent in post-combustion power plants. In this scenario, the flue gas would pass through a bed packed with a MOF material, where CO2 would be stripped. After saturation is reached, CO2 could be desorbed by doing a pressure or temperature swing. Carbon dioxide could then be compressed to supercritical conditions in order to be stored underground or utilized in enhanced oil recovery processes. However, this is not possible in large scale yet due to several difficulties, one of those being the production of MOFs in great quantities.[14]
Another problem is the availability of metals necessary to synthesize MOFs. In a hypothetical scenario where these materials are used to capture all CO2 needed to avoid global warming issues, such as maintaining a global temperature rise less than 2oC above the pre-industrial average temperature, we would need more metals than are available on Earth. For example, to synthesize all MOFs that utilize vanadium, we would need 1620% of 2010 global reserves. Even if using magnesium-based MOFs, which have demonstrated a great capacity to adsorb CO2, we would need 14% of 2010 global reserves, which is a considerable amount. Also, extensive mining would be necessary, leading to more potential environmental problems.[14]
In a project sponsored by the DOE and operated by UOP LLC in collaboration with faculty from four different universities, MOFs were tested as possible carbon dioxide removal agents in post-combustion flue gas. They were able to separate 90% of the CO2 from the flue gas stream using a vacuum pressure swing process. Through extensive investigation, researchers found out that the best MOF to be used was Mg/DOBDC, which has a 21.7 wt% CO2 loading capacity. Estimations showed that, if a similar system were to be applied to a large scale power plant, the cost of energy would increase by 65%, while a NETL baseline amine based system would cause an increase of 81% (the DOE goal is 35%). Also, each ton of CO2 avoided would cost $57, while for the amine system this cost is estimated to be $72. The project ended in 2010,estimating that the total capital required to implement such a project in a 580 MW power plant was 354 million dollars.[15]

Carbon dioxide scrubbing[edit]
Further information: carbon dioxide scrubber
Lithium hydroxide is used in breathing gas purification systems for spacecraft, submarines, and rebreathers to remove carbon dioxide from exhaled gas by producing lithium carbonate and water:[7]
2 LiOH•H2O + CO2 → Li2CO3 + 3 H2O
or
2 LiOH + CO2 → Li2CO3 + H2O
The latter, anhydrous hydroxide, is preferred for its lower mass and lesser water production for respirator systems in spacecraft. One gram of anhydrous lithium hydroxide can remove 450 cm3 of carbon dioxide gas. The monohydrate loses its water at 100–110 °C.
...
In 2012, the price of lithium hydroxide was about $5,000 to $6,000 per tonne.[8]