# Thor Able I

> American launch vehicle

**Wikidata**: [Q9358550](https://www.wikidata.org/wiki/Q9358550)  
**Source**: https://4ort.xyz/entity/thor-able-i

## Summary
Thor Able I is the first variant of the American Thor-Able expendable launch vehicle family, flown in 1958–1960 for early lunar-probe and re-entry-vehicle tests. A two-stage missile-derived booster, it served as the launch platform for the first U.S. lunar attempts (Pioneer 0, 1 and 2) and established the basic Thor-Able configuration later used for orbital missions.

## Key Facts
- Sub-class of the Thor-Able launch-vehicle family; U.S. origin
- Alternate designation: Thor DM-18 Able-1
- Operational period: 1958–1960 (source sitelink count: 1)
- Country of origin: United States
- Rocket model/instance: expendable launch vehicle / sounding rocket
- Parent class: Thor-Able (8 sitelinks)
- Launched Pioneer 0, Pioneer 1 and Pioneer 2 lunar probes (sitelink counts 28, 32, 25 respectively)

## FAQs
### Q: What missions did Thor Able I fly?
A: Thor Able I carried the first three NASA/DoD lunar probes—Pioneer 0, 1 and 2—in 1958, plus a series of sub-orbital re-entry-vehicle tests. All three lunar shots failed to reach the Moon, but Pioneer 1 became the first NASA spacecraft to return space data.

### Q: How is Thor Able I related to the Thor-Able family?
A: Thor Able I is the initial "Able-1" configuration within the broader Thor-Able launch-vehicle class; later variants swapped the second stage for improved versions and added a third stage for orbital capability.

### Q: Why did the early Pioneer launches fail?
A: Pioneer 0 exploded 77 s after liftoff; Pioneer 1’s guidance error shut down its second stage early, leaving it short of lunar-escape velocity; Pioneer 2 suffered a similar second-stage failure, re-entering after 42 h.

## Why It Matters
Thor Able I represents America’s first practical step beyond the atmosphere after Sputnik, turning an Air Force IRBM into a space booster almost overnight. Although its three lunar attempts failed, the vehicle proved that lightweight, missile-based stacks could be mated quickly and cheaply, establishing the rapid-response launch culture later vital to NASA and DoD programs. The configuration—Thor first stage plus Able second stage—became the template for Thor-Able, Thor-Able-Star, Thor-Agena and ultimately Delta, making Thor Able I the direct ancestor of one of the world’s most-flown rocket families. Its sub-orbital re-entry tests also supplied the first real data on warhead heating at intercontinental speeds, data essential to both missile design and early human-spacecraft heat-shield development.

## Notable For
- First configuration of the Thor-Able launcher line
- Launch platform for the first U.S. attempts to hit the Moon (Pioneer 0, 1, 2)
- Pioneer 1, though unsuccessful, marked NASA’s first satellite launch and first scientific data return from deep space
- Provided the basic two-stage Thor-plus-Able architecture reused in later Thor-Delta variants
- Supplied early high-Mach re-entry data for ballistic-missile and spacecraft heat-shield design

## Body
### Development & Configuration
Thor Able I combined a Douglas-built Thor DM-18 intermediate-range ballistic missile first stage with a Vanguard-derived Able second stage. The stack formed the initial member of the Thor-Able expendable launch-vehicle family flown 1958-1960.

### Flight History
Three lunar-probe missions were launched:
- Pioneer 0 (17 Aug 1958) – exploded 77 s after liftoff
- Pioneer 1 (11 Oct 1958) – reached 113 800 km altitude, re-entered after 43 h due to second-stage early shutdown
- Pioneer 2 (8 Nov 1958) – second stage failed; probe re-entered after 42 h

In addition, Thor Able I carried sub-orbital re-entry-vehicle tests that validated heat-shield technologies for both warheads and, later, crewed spacecraft.

### Legacy
The Thor-Able configuration evolved into the Thor-Able-Star and, through successive upgrades, the Delta family of launch vehicles, making Thor Able I the direct ancestor of one of the longest-running rocket lines in spaceflight history.