---
title: Constant-Acceleration Drive
type: technology
url: "https://www.envisioning.com/research/xenotech/constant-acceleration-interstellar"
hub: xenotech
summary: Fusion propulsion system designed to accelerate continuously for weeks, enabling near-light-speed interstellar travel
---

# Constant-Acceleration Drive

Fusion propulsion system designed to accelerate continuously for weeks, enabling near-light-speed interstellar travel
- Technology Readiness Level: 2/9
- Impact: 4/5
- Investment: 3/5
Constant-acceleration interstellar propulsion concepts propose maintaining steady thrust for weeks rather than brief burns, reaching relativistic speeds (~0.7c) enabling Proxima Centauri missions in ~7 years. The approach requires: compact fusion reactors with specific impulse ~10⁷ seconds (vs. chemical ~400, ion ~20,000); deuterium-lithium or advanced fusion cycles; and power-to-thrust conversion without prohibitive radiator mass.

## Advantages and Requirements

Extended acceleration offers advantages over brief-impulse trajectories: higher final velocities; mission time dominated by cruise rather than acceleration; artificial gravity during boost phase; and mid-course maneuverability. Achieving weeks of constant 1g thrust requires reactor power ~terawatts for spacecraft, exhaust velocities approaching c, and propellant efficiency far exceeding current systems.

## Current Status

Fusion propulsion is studied concept (NASA, DARPA, private ventures), but demonstrated systems remain distant. Challenges include: achieving breakeven fusion (still elusive terrestrially); compact high-power reactors; efficient thrust conversion; and thermal management. D-Li fusion offers theoretical Isp ~10⁷ through direct energy conversion, but requires advanced confinement. The constant-acceleration approach represents aspirational interstellar architecture—bridging plausible physics with engineering centuries beyond current capabilities.

---
Source: Envisioning — Technology Research Institute (https://www.envisioning.com/research/xenotech/constant-acceleration-interstellar)