# SNAP-10A

> experimental nuclear reactor launched into space in 1965

**Wikidata**: [Q1143351](https://www.wikidata.org/wiki/Q1143351)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/SNAP-10A)  
**Source**: https://4ort.xyz/entity/snap-10a

## Summary
SNAP-10A was the first nuclear reactor launched into space, deployed by the United States in 1965 as part of the Systems for Nuclear Auxiliary Power (SNAP) program. It served as a technology demonstration to test nuclear power generation in orbit. The reactor operated for only 43 days due to a non-nuclear component failure but marked a major milestone in space-based energy systems.

## Key Facts
- Launched on April 3, 1965, at 21:25 UTC from Vandenberg Space Launch Complex 4 East
- Mass: 440 kilograms
- Manufacturer: Atomics International
- Launch vehicle: Atlas SLV-3 Agena-D
- Operator: United States Air Force
- COSPAR ID: 1965-027A
- Satellite of: Low Earth orbit
- Instance of: Military satellite, technology demonstration spacecraft
- Part of: Systems for Nuclear Auxiliary Power (SNAP)
- Aliases: Space Nuclear Auxiliary Power Shot, Snapshot, OPS 4682

## FAQs
### Q: What was the purpose of SNAP-10A?
A: SNAP-10A was designed to demonstrate the feasibility of nuclear power generation in space. It was part of the U.S. SNAP program aimed at developing compact nuclear reactors for long-term space missions.

### Q: When was SNAP-10A launched and how long did it operate?
A: SNAP-10A was launched on April 3, 1965. Its reactor operated successfully for 43 days before shutting down due to a failure in an electrical component unrelated to the nuclear system.

### Q: Who built SNAP-10A and who launched it?
A: SNAP-10A was manufactured by Atomics International and launched by the United States Air Force using an Atlas SLV-3 Agena-D rocket from Vandenberg Air Force Base.

## Why It Matters
SNAP-10A represents a pioneering achievement in space exploration and nuclear engineering. As the first nuclear reactor ever launched into orbit, it demonstrated the potential for reliable, long-term power generation beyond Earth’s atmosphere—an essential capability for deep-space missions and remote installations. Although its operational life was brief, the mission provided critical data on the behavior of nuclear systems in space and laid the groundwork for future radioisotope and fission power systems. The project also highlighted the challenges of integrating complex nuclear technology with spacecraft systems, influencing safety protocols and design practices for decades to come.

## Notable For
- First nuclear reactor launched into space
- Only U.S. space nuclear reactor to have operated in orbit
- Demonstrated feasibility of space-based fission power despite early shutdown
- Used thermionic conversion to generate electricity directly from heat
- Paved the way for later radioisotope thermoelectric generators (RTGs)

## Body
### Mission Overview
SNAP-10A was developed under the broader Systems for Nuclear Auxiliary Power (SNAP) program, which sought to provide lightweight, long-life power sources for space missions. The spacecraft was intended to validate nuclear power generation in the vacuum of space and support future military and scientific applications.

### Technical Specifications
The spacecraft carried a compact fast-neutron reactor fueled with highly enriched uranium-235. Key components included:
- Reactor core: 38 cm in height, 56 cm in diameter
- Thermionic fuel elements (TFEs) for direct thermal-to-electrical conversion
- Hydrazine thrusters for attitude control
- Radiator fins for thermal management

Total mass at launch was approximately 440 kg, including structural components and shielding.

### Launch and Orbit
Launched on April 3, 1965, via Atlas SLV-3 Agena-D from Vandenberg Space Launch Complex 4 East, SNAP-10A entered a near-polar low Earth orbit. The mission was managed by the United States Air Force, reflecting its dual-use potential for both civilian and defense purposes.

### Operational History
The reactor achieved criticality on April 3, 1965, and began producing electrical power shortly thereafter. However, after 43 days of operation, the mission ended prematurely when a voltage regulator in the power conditioning subsystem failed—unrelated to the nuclear reactor itself. Despite this, valuable performance data were collected during the active period.

### Legacy and Impact
Although SNAP-10A's operational lifespan was limited, it remains the only nuclear fission reactor ever flown by the United States in space. The mission contributed significantly to understanding materials behavior, thermal dynamics, and radiation effects in orbital environments. Lessons learned informed subsequent designs such as those used in radioisotope thermoelectric generators (RTGs), which continue to power interplanetary probes today.

## References

1. Jonathan's Space Report
2. Freebase Data Dumps. 2013