Thursday, 28 January 2016

Space Habitat: West Sphere and Leisure.


           According to some of my reading a spherical space habitat is the optimum with respect to containment of air pressure and mass-efficiency at providing radiation shielding. The shape also the likely result of construction methods such as the bubbleworld technique. The downside of a spherical habitat is that only a small proportion of the interior will be at maximum centripetal gravity.

           My solution to this, the West Sphere, is to construct a cylindrical surface within the interior of the sphere. The following illustration depicts a 2.23km diameter sphere with a 1.78km diameter cylinder within. If the sphere rotates at one revolution per minute the centripetal gravity on the inner surface of the sphere will be the equivalentof 1g. The cylinder is 1.35km long in this illustration so the potential 1g area is more than 7.5 million square metres.


           The volume of habitat under/outward of the cylinder floor will be subject to higher centripetal forces of between 1g and 1.25g. Such g levels are tolerable for short periods of time but these areas are probably not suited to long term human occupation. Instead the higher g levels will be used for a number of other purposes. Drainage and sewage processing for the living areas is an obvious application. Many sections of this area may be used for storage. Many automated industrial processes could be located in these levels. It is possibly that some industrial processes might be facilitated by higher gravity levels. An interesting application for the higher g levels is for gymnasiums and exercise areas. A number of jogging and cycling tracks may be located in these levels. Tracks at differing levels may be interconnected by ramps so athletes can vary how much of their training is at higher gravity levels.

           The spherical habitat will be spun with one pole towards the sun. The solar pole will be shielded against radiation by a mass of rock. The anti-solar pole will be provided with windows and shutters. External mirrors will reflect sunlight through these windows and onto the inner surface of the cylinder. Somewhat confusingly, sunlight comes from the anti-solar end of the habitat! The shutters will allow the light level to be varied and could be used to simulate a day and night cycle. It is possible in some habitats no attempt will be made to simulate night and day. In some parts of the Earth humans function very well with months of constant daylight. Housewives in Reykjavik do their gardening in the middle of the “night” so it is possible some habitats will not bother with nigh time, or at least not full levels of darkness.

           The main docking area for spacecraft is likely to be situated at the solar pole near the axis. Visitors will initially be weightless. To reach the cylinder surface they will have to travel down the inside of the sphere at the solar end, possibly using some form of funicular. The lower the carriage gets the heavier they seem to become.

           Alternately the visitor may travel down the zero g central axis of the habitat. This will be a rapid route for moving passengers or freight to locations on the cylinder surface. A number of possibly transport options can be used here, ranging from zero g trains or cable cars to simple tubes were that individuals can simply free-fall (or get blown) along. A key points tall elevator towers reach up from the cylinder surface like the spokes of a wheel and intersect the central axis, allowing travellers to descent or ascend.


           The gravity gradient of the habitat allows for a number of novel leisure activities. Fitness training in the higher g levels has already been described. The lower gravity levels above the cylinder’s surface allow for some interesting airborne sports. Manpowered flying machines will be quite practical, providing the flyer does not descend too low. Flight by flapping a pair of strapped on wings is also possible. Batsuits, such as worn by modern parachutists (above), could potentially stay airborne for hours at a time if flown competently. The elevator towers described above are likely to include various flight centres and rentals on their intermediate levels.


           An interesting proposal for the space habitat is the low-gravity swimming pool. This would take the shape of a torus-shaped trough of water of a smaller diameter than the habitat. This will be at the anti-solar end of the habitat so that it does not intersect the axial transportation systems. You will have to ascend to go swimming. The pool may rotate at the same speed as the space habitat or be spun at a slightly faster rate, depending on its diameter and the desired surface gravity. Swimming in such a pool will be a novel experience since the water surface will curve upwards. The lower gravity will have a number of interesting effects. If you bounce on the diving board enough you can fly straight upwards and dive into the water above your head! Lower gravity means that sports such as water polo will become less taxing and possible for a greater variety of players who no longer have to use most of their energy staying above the surface. In addition, or instead of the torus-shaped pool some facilities will include a large “bubble” of water at the zero g axis of the habitat. This “pond” will allow swimming in zero gravity. Gravityless swimming is also without buoyancy so there is a potential danger that someone swimming in the “pond” may become disorientated and drown before they can reach the spherical surface. To counter this the pond will be interlaced with brightly coloured guide lines which also incorporate airlines and breathing mouthpieces at frequent intervals. These lines also replenish the pond by pumping water into it. Without this system the pond will diminish as splashed water descends to the surrounding torus pool. It is possible to swim all the way across the pond and then fall/dive into the torus pool. This will bring a whole new significance to the lifeguard’s command of “no bombing!”


           It is not just sports that will take on new aspects in a space habitat. Ballet and some other dance disciplines in reduced gravity will have many new facets, with dancers leaping dozens of metres and staying airborne for seconds at a time. To exploit this ballet theatres in habitats will be built at the top of towers or tall buildings.

 

Tuesday, 26 January 2016

Greyhounds, Couriers and Packets.


Greyhounds (also known as Courier or Packets) are relatively small space vessels. Greyhounds are used for the rapid transport of very high value individuals and materials. Their passenger accommodation, if any, is very basic and passengers are typically transported in nanostasis. Most of the ship is taken up by the drive, fuel and reaction mass. The purpose of the greyhound is to rapidly move objects from one place to another.   Greyhounds vary considerably. Some can carry a small party, others just one or two people and others can only carry packages smaller than a baseline human.
Some greyhounds may be piloted by a human but AI piloting is more common. Many things that are moved by greyhound are confidential and the memory of an AI pilot is easier to erase.  Information too sensitive to be broadcast may be transported on a data core in a greyhound. Greyhounds may incorporate various systems to prevent their cargo being intercepted, tampered with or stolen.

Tuesday, 19 January 2016

Weapons: 40x225mm Super Forty


The CTAI CT2000, 40x225mmCTA Super Forty is a rival to the 50mm Supershot and appears currently to be the preference of the USMC and British Army. The Pyramid article suggests that it will arm IFVs and other vehicles till 2050. Given the British tradition of “making do” and defence cuts it is likely vehicles with these weapons are still be “soldiering on” in 2100. US-made vehicles with these weapons may have been given to allied nations as military aid.

The Super Forty fires 40 x 225mmCTA rounds with a plastic case. A version of the Bushmaster is offered that fires this round or 30 x 176mm or 30 x 170mm cannon rounds. This system is often referred to as a 30/40mm and this term may be used for other weapons of this chambering. The CT2000 had a linkless triple-feed system. The Bushmaster Mk44 is 343lb; Rof: 3 or 7; Dual belt feed.
            Apart from standard ammunition, CTAI also designed a guided APEDS-CLGP round, which fired a saboted, armor-piercing tungsten projectile with a HE charge. This laser-guided 25mm dart was modified from the submunitions of the British Starstreak surface-to-air missile. By the TS-era homing ammunition will doubtless have been developed for this cannon.

Name  Ammo  Damage  Acc  Range  RoF  Ewt  WPS  VPS  CPS  Pow  Notes
CTAI CT2000  APFSDS
6d x 11(2) 8
4,500/18,000
  6
  725
4.0
 0.015
 $110
 9kW
 

 
 AHEAD
6d x 6(0.5) plus 3d[4d(2)]
7

3,500/9,000

 

 

4.8

 

$110

 

[1]

 
APEDS-CLGP
6d x 6(2) plus 1d[2d] cr ex
7

4,000/12,000

 

 

4.2

 

$833

 

 
    HEPF6d[4d] cr ex   7 4,000/10,000   4.8   
    [2]

 
[1] AHEAD ammunition is effectively a shrapnel shell (HT 4e p.173) that can be programmed to explode at a range set at the moment of firing. It is primarily intended to engage airborne targets. The 3e Damage stat above is rather unrealistic for a round of this type. Explosive content would actually be a modest ejection charge. I have no specific data for the 30/40 AHEAD round. Online sources claim a 30mm version of the AHEAD contains 150 pellets but this may be confusion with the original 35mm round containing 152 tungsten pellets. 6d x 6(0.5) pi++ should be considered the KE damage from an intact shell. Using the rules in HT 4e p.166 & 172 based on 6d x 6 damage the pellets of an AHEAD are 3d(2) pi; RoF x 150; Rcl 1 The pellets get an armour-piercing modifier for being tungsten and high-velocity.
[2] The original table did not include any explosive round for the Super Forty. The HEPF is a programmable-fused airburst round based on the stats for a 40mm shell, reflecting improved explosive compositions in the TS-era.

Monday, 18 January 2016

Flight times for Homing Ammunition.


            When firing homing rounds they may take more than one turn to reach the target. Basic rules (B p.413) say to use any 1/2D figure as projectile speed but this doesn’t really work for small arms. The following values can be used instead to give a simple but reasonably realistic performance. Bullets get slower the further they get from the muzzle so for the second and subsequent rounds speed is generally halved.
            Projectiles that travel at 375 yards/sec or faster exceed the speed of sound, creating a very audible bullet-crack.

·         15mm micro-missiles and 30mm mini-missiles: 500 yard/sec. (Will usually hit in same turn that they are fired).
·         20mm micro-missiles: 400 yard/sec.
·         40mm mini-missiles: 295 yards/sec.
·         4mm and 10mm pistol/PDW: 350 yards in first second, 175 yards each second after. (The 4mm has a higher muzzle velocity but the 10mm retains more energy down range so for convenience average velocity is treated as the same for both). Muzzle velocity exceeds the speed of sound.
·         5.6mm and 6.6mm rifle: 600 yards in first sec, 300 yards each second after. (Higher muzzle velocity of the 5.6mm is balanced out by better sectional density of the 6.6mm so average velocity is treated as the same.)
·         7.62x39mm AKM/Maku: 500 yards first sec, 250 yards each second after. Generally these weapons use non-homing ammunition.
·         7.5mmMG: 700 yards first sec, 350 yards each second after. Uses a heavy streamlined bullet designed for target effect at long range.
·         9mm MAX and Subsonic Ammunition: Treat as 300 yards first sec, 150 yards each second after. Generally 9mm MAX weapons use non-homing ammunition.
·         Plastic Ammunition : Half speed of standard type (therefore Plastic subsonic ammunition is 150 yards in first second, 75 yards each second after.)
·         Supercavitating 15mm mini-torpedoes are move 25 for the first second, Move 40 for the next two.
·         Supercavitating 30mm mini-torpedoes are move 30 for one second, Move 80 for the next three.
·         Supercavitating ammunition fired underwater has 1/10th the speed of a normal round of the calibre.

 

Weapons: AKM and Maku


            At the dawn of the 22nd century the AK-47/AKM still continues to soldier on. Most of the weapons in active use are minifactured or 3D printed replicas, of course, but the Kalashnikov is still a common sight in many of the remoter parts of the world or even off-world. Some have even been forged by village blacksmiths rather than printed!

            For many users their choice may be due to tradition, practicality or conservatism. The AK was good enough for granddad and still does the job, so who needs a high-tech, far more expensive weapon? Many isolationist groups prefer weapons with cased ammunition that they can reload. AKMs are favoured by many ceremonial guard units, particularly if the weapon is also featured on the national flag. 

            “Maku” the street name for a version of the AKM that is manufactured illegally in many urban areas. It is readily recognized by its crude finish. The fore-end is usually a section of plastic pipe and the stock shaped scrap. Sights are often crude affairs and fixed. The foresight may be either mounted at the muzzle or the top of the gas tube. Rear sight also varies in position and may be either a simple notch or aperture. Despite its ugly duckling appearance the Maku is still an AKM inside.

            Note: I have changed the Damage of the AKM et al to 4d+4 to represent that compared to the 5.56x45mm the 7.62x39mm round often exhibits less spectacular but more consistent terminal effects.

GUNS (RIFLE) (DX-4 or most other Guns at -2)
 
  Name  Damage  Acc   Range  Weight  RoF  Shots  ST  Bulk  Recoil
AKM 7.62mm   4d+4 pi   4  500/3,100   8.7/1.8   10   30(3)   9†  -5/-5*   2
Maku 7.62mm   4d+4 pi
  3
 500/3,100
  11/1.8
  10
  30(3)
  9†
  -5
  2
APHC ammo
CPSx2
  4d+4(2) pi-