---
type: claim
domain: space-development
description: "DARPA/NASA DRACO program ($499M) has successfully tested reactor fuel with in-orbit engine activation planned for 2026-2027, offering ~900s specific impulse vs 450s chemical"
confidence: likely
source: "Astra, web research compilation February 2026"
created: 2026-02-17
depends_on:
- launch cost reduction is the keystone variable that unlocks every downstream space industry at specific price thresholds
related:
- Nuclear electric propulsion (NEP) provides higher efficiency for uncrewed cargo missions while nuclear thermal propulsion (NTP) remains superior for crewed time-constrained missions
- repurposing-sunk-cost-hardware-for-new-missions-can-accelerate-technology-deployment-timelines-by-5-10-years-compared-to-clean-sheet-programs
reweave_edges:
- Nuclear electric propulsion (NEP) provides higher efficiency for uncrewed cargo missions while nuclear thermal propulsion (NTP) remains superior for crewed time-constrained missions|related|2026-04-17
- repurposing-sunk-cost-hardware-for-new-missions-can-accelerate-technology-deployment-timelines-by-5-10-years-compared-to-clean-sheet-programs|related|2026-04-17
---

# Nuclear thermal propulsion cuts Mars transit time by 25 percent and is the most promising near-term technology for human deep-space missions

Nuclear thermal propulsion (NTP) achieves approximately 900 seconds of specific impulse -- roughly double chemical propulsion's 300-450 seconds -- while maintaining comparable thrust levels. This combination of efficiency and thrust is unique among propulsion technologies: ion thrusters achieve 3,000-5,000 seconds specific impulse but produce only millinewtons of thrust (ideal for cargo, not humans). NTP cuts Mars transit time by approximately 25%, which is not just a convenience but a significant reduction in mission risk -- less radiation exposure, fewer consumables, shorter vulnerability windows.

The DARPA/NASA joint DRACO program ($499 million) is advancing NTP toward flight testing. General Atomics successfully tested reactor fuel at Marshall Space Flight Center in January 2025. In-orbit engine activation is planned for early 2026, though the schedule may slip to 2027. Two contractors (Ultra Safe Nuclear and General Atomics) are advancing development. This represents the most concrete progress toward nuclear propulsion since the NERVA program was cancelled in 1972.

NTP is a technology dependency in the chain leading to sustained human presence beyond LEO. Chemical propulsion can reach Mars but imposes transit times that create unacceptable risk profiles for crewed missions. Ion propulsion can move cargo efficiently but too slowly for humans. NTP occupies the sweet spot: fast enough for human transit, efficient enough to be practical.

## Evidence
- DRACO program: $499M, General Atomics reactor fuel testing (January 2025)
- NTP specific impulse: ~900s vs 300-450s chemical, vs 3,000-5,000s ion
- Mars transit reduction: ~25% (from 7-9 months to 5-7 months)
- NERVA heritage program (cancelled 1972) demonstrated feasibility

## Challenges
DRACO was partially cancelled in 2025 though congressional funding continues at $110M+. Political and regulatory barriers to launching nuclear material remain significant. No flight demonstration has occurred since the 1960s NERVA tests.

---

Relevant Notes:
- [[launch cost reduction is the keystone variable that unlocks every downstream space industry at specific price thresholds]] — getting to orbit is half the problem; NTP addresses moving between destinations efficiently
- [[the Moon serves as a proving ground for Mars settlement because 2-day transit enables 180x faster iteration cycles than the 6-month Mars journey]] — NTP would compress Mars iteration cycles

Topics:
- [[space exploration and development]]