Impulse drive

• Short for "internally metered pulse drive" (Invasion Novel: First Strike)
• Main Federation sublight drive system
  • Description guided by both TNG technical manual and general description in Final Frontier, in order to best fit qualities on-screen inconsistent with straightforward Newtonian drive
  • Based on deuterium-fed laser pulse fusion reactor generating high energy electroplasma compatible with internal EPS power systems
    • Early systems occasionally also based on tritium fusion (TNG Novel: A Time to Sow)
    • First generations of impulse fusion reactors produced neutron radiation as a byproduct, requiring extensive radiation shielding (TNG Novel: A Time to Sow)
  • Combination of Newtonian and non-Newtonian propulsion (DS9 Novel: Gamma: Original Sin)
    • Fusion reaction captured by artificial gravitational field, subspace field effects to hypercompress released energy, generating spatial distortions to linearly propel vessel either forward or in reverse
    • Velocity aided and vectored by expulsion of reactants under effect of a subspace field driver coils, increasing reactant mass and reducing vessel mass to increase effectiveness of Newtonian propulsion (TNG Tech Manual)
  • As of 2270s, impulse operation also incorporates low-level warp field to reduce vessel inertial mass (TOS Novel: Ex Machina; TNG Tech Manual)
    • Soon after implementation, led to impulse velocities sometimes being referred to as fractional warp velocities, though this practice was soon dropped (Star Trek: The Motion Picture; TOS Novel: Ex Machina)
  • Maximum impulse velocity limited to 0.25c by policy, to prevent severe relativistic effects from bringing vessels too significantly out of sync with rest-frame activities (TNG Tech Manual)
    • Up to 0.75c in emergency situations (TNG Tech Manual)

History

• 2018: Invented by Earth, quickly displacing other engine technologies
• Late-21st century: First redesigns to incorporate subspace features, increasing potential delta-V