From Pressure Hulls to Trussed-Macrofilaments: Structural Techniques

From Pressure Hulls to Trussed-Macrofilaments: Structural Techniques by Pope Torak

The mission requirements of Starfleet starships require that they combine a mixture of impossible material qualities. Hulls are expected to simultaneously be light, hard, tough, with good thermal properties to withstand both extremes of high and low temperature. As a consequence construction techniques reflected the need of yard engineers to bridge the gap between demands of designers and the reality of materials science.

Starfleet hull design initially followed a combination of UESF, Andorian and Vulcan traditions, emphasizing the use of high density duranium alloys in the outer pressure hulls with rigid bulkhead construction. Internal partitions and structures served as part of the starship's loadbearing structure. Interspersed between rigid duranium alloy frames were ceramic heat dissipation materials and ductile polymers entwined at nanomaterial scales to provide a form of hull insulation. Pressure hulls were armored with a layer of ceramic thermal dissipation material and yield inducing cushioning. This was then covered with high-density armor plating formed of a polarizable duranium-tungsten alloy which could be easily replaced after a firefight. Polarized hull plating provided near immunity from kinetic kill weaponry, but suffered from problems with thermal conductivity from high thermal energy weapon like particle weaponry and fusion munitions.

Advances in graviton based shields in the 23rd century encouraged Starfleet to forego high density armor plating on the exterior of their starships. Instead the pressure hulls were coated with a white-grey thermal coating which helped protect the vulnerable pressure hull from energy weapon discharges and stellar phenomenae.

Unlike the semi-monocoque pressure hull designs of the Columbia or Daedalus classes, starships of the 23rd century were primarily built from internal frame construction with an empashis on resisting compression forces. Transverse bulkheads were common on all Starfleet designs in this era, the result creating tall, but inflexible cooridors within the internal hull. When additional material strength was required, a limited form of polarization could be used on internal bulkheads to strengthen the hull during high periods of stress such as during warp acceleration.

The emphasis on internal framing was also based on the reality that Starfleet ships faced frequent replacement and repair of external hull components in this era. In particular the thermal coat would often face damage from highly concentrated plasma weaponry like Romulan designs or more tightly confined energy weapons like Klingon disruptors. The intent was to allow most of the energy to be absorbed and scattered by the thermal coat, leaving key structural frames intact.

The advantage of this method of construction was evident when Starfleet proceeded with the Constitution-class refit program in the 2270s. The differentiation of the ship components from the internal frames allowed Starfleet to essentially strip Enterprise to her bones and rebuild her with new components. The main drawbacks to this method of construction were the relative inefficient use of spaceframe volume, significant mass, limited modularity of internal compartments, and a general limit on frame size.

Two-layer forcefield designs which vastly improved thermal dissipation allowed Starfleet to do without the heavy ceramic based thermal coat. Additionally, lighter and more ductile trititanium was used for outer hull segments. The combination of the two innovations allowed Starfleet starships in the 2270s to 2290s to substantially improve in performance metrics over their predecessors of the 2260s.

However, it was clear by 2280 that Starfleet's older cruiser designs were beginning to suffer from structural fatigue. Internal frame components were difficult to replace without replacing the entire vessel, and Starfleet Engineering sought a way to extend the lifespan of these ships without a costly rebuild. The solution was provided by Salazaar's half-aenar master shipwright Be'tham Assam. A series of light tritanium metal truss and riders were inserted between ceiling panels of the bulkhead compartments. Each of these trusses were then reinforced with a variable strength version of hull polarization, adjusting their strength as required by hull stresses.

Designers of the Excelsior-class project immediately latched onto the increased hull strength provided by the arrangement. Captain Sephara Rule developed a system combining reinforced alloyed trusses against an external stress hull. The stress hull replaced the concept of a sealed pressure hull and substantially reduced the need for an internal compression hull. The initial prototype NX-2000 was not equipped with a fully fledged structural integrity field as concerns existed about the stability of subspace based graviton forcefields under transwarp conditions. Still, the first use of a trussed frame based external hull skeleton with gamma welded stress hull was a significant step forward in starship construction.

Subsequent production of conventional warp drive Excelsior-class starships allowed ASDB to test the idea of a subspace forcefield based structural integrity field. Compared to traditional IMRF and alloy polarization combinations that were limited to strength increases in the 1-4,000% range, the new truss-integrated SIF emitters allowed structural strength increases of up to 25,000%. This made the basic Excelsior-class frame substantially stronger than existing designs. This additional structural strength enabled everything from greater sublight and warp acceleration to greater space frame endurance.

Improvements to existing starship designs were just as pronounced. Although the Miranda-class of 2310 was externally identical to the same design from 2270, the hull featured a structural strength nearly ten times greater at full load. Primary hull internal volume was increased by 25%, while hull mass decreased from 3 tons/m³ to 1.9 tons/m³. On the whole this allowed the ships to triple their maximum impulse acceleration and the hull to withstand the stress generated by higher density warp coils of the latest generation of LN-64 based designs. For the crew this meant substantially improved habitability conditions and a greater mission endurance.

Construction in the 24th century followed up with larger and more ambitious applications of SIF-integrated trussed-frame designs. Comparison of ships named Enterprise is instructive. NCC-1701-A had a payload volume of 280,000 m³. Commissioned just 10 years later, her Excelsior-class successor featured 975,000 m³. The following half-century would introduce NCC-1701-C with 2,800,000 m³ which in turn would be dwarfed by NCC-1701-D's 5,800,000 m³ in 2363. The Sovereign class featured a slightly smaller volume, but NCC-1701-E's trussed-frame is capable of a 200,000% increase in materials strength compared to NCC-1701-B's 25,000%.

The materials themselves underwent a substantial improvement as well. Phase-transition bonding allowed seamless creation of outer stress hulls that mixed the best characteristics of duranium and trititanium. Improvements in subspace field modulated graviton manipulation nanoscale crystal formation by 2350 allowed the refinement of unalloyed tritanium latices, which could then be phase-transition bonded to duranium to form lighter, stronger trussed frames. Ships built in the 2360s featured substantial improvements to their overall hull integrity due to these material advancements.

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