---
type: entity
entity_type: protocol
name: Space Reactor-1 Freedom (SR-1 Freedom)
domain: space-development
status: active
launch_date: 2028-12
supports:
- nuclear thermal propulsion cuts Mars transit time by 25 percent and is the most promising near-term technology for human deep-space missions
- 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 thermal propulsion cuts Mars transit time by 25 percent and is the most promising near-term technology for human deep-space missions|supports|2026-04-17
- Nuclear electric propulsion (NEP) provides higher efficiency for uncrewed cargo missions while nuclear thermal propulsion (NTP) remains superior for crewed time-constrained missions|supports|2026-04-17
- repurposing-sunk-cost-hardware-for-new-missions-can-accelerate-technology-deployment-timelines-by-5-10-years-compared-to-clean-sheet-programs|supports|2026-04-17
---

# Space Reactor-1 Freedom (SR-1 Freedom)

**Type:** Nuclear electric propulsion spacecraft  
**Status:** Active development, launch scheduled December 2028  
**Organization:** NASA  
**Mission:** First nuclear-powered spacecraft to travel beyond Earth orbit (uncrewed Mars mission)

## Overview

Space Reactor-1 Freedom is NASA's first operational nuclear-powered interplanetary spacecraft, announced March 24, 2026 alongside the Gateway program cancellation. The spacecraft repurposes the Gateway Power and Propulsion Element (PPE) — already completed and validated hardware — for a nuclear electric propulsion demonstration mission to Mars.

## Technical Architecture

**Propulsion:** Nuclear Electric Propulsion (NEP)
- Nuclear fission reactor generates electricity
- Electricity powers ion thrusters
- Distinct from Nuclear Thermal Propulsion (NTP) where nuclear heat directly expands propellant
- Provides specific impulse of ~3,000-10,000 seconds (vs NTP ~900s, chemical ~450s)
- Lower thrust than NTP but higher efficiency, optimized for cargo missions

**Hardware Origin:** Gateway Power and Propulsion Element (PPE)
- Most expensive and technically complex component of the canceled Gateway program
- Already completed and qualified hardware
- Featured advanced solar-electric propulsion combined with compact fission reactor

## Mission Profile

- **Destination:** Mars (uncrewed)
- **Launch:** December 2028
- **Significance:** First nuclear propulsion system moving from R&D to operational program
- **Mission objectives:** Not clearly specified in initial announcement (unclear if primarily propulsion demonstration or includes science payload)

## Strategic Context

Represents a 5-10 year acceleration of nuclear propulsion deployment compared to a clean-sheet program by leveraging already-qualified hardware. Demonstrates NASA's prioritization of cargo/infrastructure delivery for near-term nuclear propulsion applications rather than crewed transit.

## Timeline

- **2026-03-24** — Program announced at NASA Ignition event alongside Gateway cancellation
- **2028-12** — Scheduled launch date

## Sources

- NASASpaceFlight, March 2026
- NASA official announcement, March 24, 2026
- Futurism coverage
- New Space Economy analysis