---
type: entity
entity_type: protocol
name: SR-1 Freedom
parent_org: NASA
domain: space-development
secondary_domains: [energy]
status: active
announced: 2026-03-24
launch_date: 2028-12
supports:
- 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|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
---

# SR-1 Freedom

**Type:** Nuclear Electric Propulsion (NEP) spacecraft  
**Mission:** Mars transit demonstration  
**Launch:** December 2028  
**Status:** Active development

## Overview

SR-1 Freedom is NASA's first nuclear-powered interplanetary spacecraft, announced March 24, 2026 alongside Project Ignition. It repurposes Gateway's Power and Propulsion Element (PPE) as the propulsion system for a nuclear electric spacecraft.

## Technical Architecture

**Propulsion:** Nuclear Electric Propulsion (NEP)
- Ion thrusters powered by fission reactor
- Distinct from Nuclear Thermal Propulsion (NTP)
- Uses Gateway PPE (already built) as propulsion module

**Mission Profile:**
- Launch: December 2028
- Destination: Mars transit demonstration
- Objective: Validate NEP for deep-space operations

## Strategic Context

SR-1 Freedom represents NASA's pivot to nuclear propulsion for interplanetary missions. The repurposing of Gateway's PPE (following Gateway's cancellation) demonstrates adaptive reuse of existing hardware to accelerate nuclear propulsion development.

**NEP vs NTP distinction:** Nuclear Electric Propulsion (ion thrusters + reactor) provides high specific impulse but low thrust, suitable for cargo missions. This is architecturally different from Nuclear Thermal Propulsion (heated propellant) which provides higher thrust for crewed missions.

## Timeline

- **2026-03-24** — SR-1 Freedom announced; Gateway PPE repurposed as propulsion module
- **2028-12** — Scheduled launch to Mars

## Related Programs

- [[project-ignition]] — Lunar surface program announced simultaneously
- [[gateway]] — Cancelled program whose PPE module was repurposed

## Sources

- Singularity Hub: "NASA Unveils $20B Moon Base Plan and Nuclear Spacecraft for Mars" (March 27, 2026)
- NASA.gov: "NASA Unveils Initiatives to Achieve America's National Space Policy" (March 24, 2026)