The year 1951 saw extensive exploration of space by the United States and the Soviet Union (USSR) using suborbital rockets. The Soviets launched their first series of biomedical tests to the 100-kilometre (62 mi) boundary of space (as defined by the World Air Sports Federation). Several American agencies launched more than a dozen scientific sounding rocket flights between them. The US Navy launched its Viking sounding rocket for the seventh time since 1949, this time to a record-breaking 136 miles (219 km) in August 1951.

Development also continued by both superpowers on rockets more powerful than the World War Two era German V-2 that had inaugurated the age of spaceflight. The USSR advanced far beyond their R-1 (a V-2 copy) with the deployment of the R-2 rocket, which could carry a ton of explosives twice as far as its predecessor. Though the ambitious Intermediate Range Ballistic Missile was canceled in 1951, the more achievable R-5 missile project was initiated. Both the US Air Force and the US Army initiated their first post-V-2 ballistic missile projects, Atlas for the former and Redstone for the latter.

The US Army, US Air Force, and the Applied Physics Laboratory continued their use of Aerobee on a variety of physics, aeronomy, photography, weather, and biomedical sounding rocket flights; a total of 11 were launched during the year. Two of these comprised the earliest space biomedical missions. Launched by the Air Force, and carrying mice and monkeys, they (along with a third flight in 1952) determined that brief (approx. 15 minutes) exposure to acceleration, reduced gravity, and high altitude cosmic radiation did not have significant negative effects.

The first generation of US Navy-built Viking sounding rockets reached its acme of performance with the flight of Viking 7, the sole Viking launch of 1951. Launched 7 August from White Sands Missile Range in New Mexico, the rocket set a new world altitude record of 136 miles (219 km).

The R-1, the Soviet Union's first domestically built long-range ballistic missile, was accepted into service in November 1950. In January 1951, cold-weather testing of the R-1 for quality assurance purposes was conducted. On 1 June, production of the R-1 was centralized and transferred to a former automobile factory in Dnepropetrovsk, and that month, a test series of R-1s was successfully launched to the edge of space, all landing within 5.5 kilometres (3.4 mi) of their targets. Though the R-1, a virtual copy of the now-obsolete V-2, was not a particularly formidable weapon and posed virtually no threat to the West, it was invaluable in training engineers and missile crews, as well as creating a nascent rocket industry in the Soviet Union.

On 29 January 1951, dogs were carried on one of the winter test flights of the R-1. This was followed in the summer by six R-1s specifically designed and equipped for biomedical flights to determine if their payload dogs could survive the rigors of space travel and be recovered. Three of the missions were successful. On July 22, 1951, Dezik and Tsygan became the first Soviet space dogs to be launched into sub-orbital spaceflight.

The R-2 missile, the first operational Soviet design to have a separable nose cone, underwent a second test series of thirteen flights in July 1951, experiencing one failure. Accepted for operational service on 27 November 1951, the design had a range of 600 kilometres (370 mi), twice that of the R-1, while maintaining a similar payload of around 1,000 kilograms (2,200 lb).

By 1950, the war-head carrying ballistic missile, which in the United States had been eclipsed since World War II by guided missile development, received national priority. In January 1951, the US Air Force's Air Research and Development Command awarded to Consolidated Vultee the contract for Atlas, the nation's first Intercontinental ballistic missile. The Atlas went on to become one of the key boosters in America's crewed and robotic space programs, first orbiting a payload (SCORE) in 1958.

On 15 April 1950, Wernher von Braun and his team of German rocket engineers were transferred from Fort Bliss to Redstone Arsenal in Alabama. In 1951, the Redstone team was tasked with researching and developing guided missiles and developing and testing free rockets, solid propellants, Jet-Assisted Take-off rockets, and related items, thus making the Army a leading player in America's missile development. Their work led to the production of the Redstone missile, first launched in 1953, versions of which ultimately launched Explorer 1, America's first artificial satellite, in 1958, and Mercury-Redstone 3, America's first human space mission, in 1961.

In the summer of 1950, the United States Naval Research Laboratory (NRL) team led by Milton Rosen began work on an improved Viking rocket able to reach higher altitudes. The team would achieve increased performance through larger fuel tanks and reduced weight elsewhere on the rocket. Originally planned for launch in 1951, the development of the second generation Viking took two years, and the first of the new rockets would not launch until 6 June 1952.

In January 1951, Dr. James Van Allen, instrumental in the development of the Aerobee rocket, joined the physics department at the State University of Iowa (SUI). Along with University of Chicago graduate Melvin B. Gottlieb and Van Allen's first SUI graduate student, Leslie H. Meredith, they began a high altitude cosmic ray research program using equipment mounted on balloons. Launched from 16 June 1951, through 26 January 1952, this experience set the foundation for balloon-launched sounding rockets, which would first breach the boundary of space in 1954.

From 1947, G-1 (or R-10) missile, designed by German specialists brought to the USSR in 1945 to work on missile projects, competed with the Soviet-designed R-2 for limited engineering and production staff, the latter winning out by the end of 1949. With the project stalled for a lack of resources and government interest, the Soviets terminated all work by the German specialists in October 1950. In December 1951, the first of these Germans were repatriated to East Germany (a process that the Soviets completed in November 1953).

The draft plan for the ambitious 3,000-kilometre (1,900 mi) range R-3 had been approved on 7 December 1949, but was canceled on 20 October 1951, other designs proving more useful and achievable. One of them was the R-5 missile, able to carry the same payload as the R-1 and R-2 but over a distance of 1,200 kilometres (750 mi) (the other being the R-11, a tactical missile half the size of the R-1 but with the same payload). The R-5's conceptual design was completed by 30 October 1951.

← Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec →

January launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
18 January 20:14	V-2		V-2 No. 54	White Sands LC-33		GE / US Army
			NRL	Suborbital	Cosmic Radiation / Solar UV / Solar X-Ray	18 January	Launch failure
		Project Hermes launch, Apogee: 1.61 kilometres (1.00 mi), very low thrust
22 January 22:55	Aerobee RTV-N-10		A19	White Sands LC-35		US Navy
			APL	Suborbital	Aeronomy	22 January	Successful
		Apogee: 89 kilometres (55 mi)
25 January 15:00	Aerobee RTV-N-10		A20	White Sands LC-35		US Navy
			APL	Suborbital	Ozone Aeronomy	25 January	Successful
		Apogee: 90 kilometres (56 mi)
29 January	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	29 January	Successful
		Carried dogs
30 January	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	30 January	Successful
31 January	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	31 January	Successful

February launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
1 February	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	1 February	Successful
2 February	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	2 February	Successful
6 February 17:20	Aerobee RTV-N-10		A21	White Sands LC-35		US Navy
			APL	Suborbital	Photography	6 February	Successful
		Apogee: 98 kilometres (61 mi)

March launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
9 March 03:16	V-2		V-2 No. 57	White Sands LC-33		GE / US Army
		Blossom IVE	Air Materiel Command	Suborbital	Solar X-Ray / Aeronomy / Ionospheric / Airglow	9 March	Launch failure
		Project Hermes launch, apogee: 3.1 kilometres (1.9 mi), explosions starting at 15.5 seconds destroyed the tail section
28 March 23:14	Aerobee RTV-A-1		USAF 10	Holloman LC-A		US Air Force
			AFCRL	Suborbital	Aeronomy	28 March	Successful
		Apogee: 66 kilometres (41 mi)

April launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
12 April 17:26	Aerobee RTV-A-1		USAF 11	Holloman LC-A		US Air Force
			AFCRL / University of Colorado	Suborbital	Solar UV	12 April	Partial failure
		Apogee: 29 kilometres (18 mi), premature engine cutoff at 30.6 seconds
18 April 18:39	Aerobee RTV-A-1		USAF 12	Holloman LC-A		US Air Force
		Aeromed 1	AFCRL / WADC Aero-Medical Laboratory	Suborbital	Biological	18 April	Successful
		First biomedical Aerobee mission, carried monkey; apogee: 61 kilometres (38 mi)

May launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
29 May 19:46	Aerobee RTV-A-1		USAF 13	Holloman LC-A		US Air Force
			AFCRL / Boston University	Suborbital	Ionospheric	29 May	Launch failure
		Apogee: 3.7 kilometres (2.3 mi)

June launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
8 June 00:11	Aerobee RTV-A-1		USAF 14	Holloman LC-A		US Air Force
			AFCRL	Suborbital	Solar X-Ray / Aeronomy	8 June	Successful
		Apogee: 89 kilometres (55 mi)
8 June 01:18	Aerobee XASR-SC-1		SC 19	White Sands LC-35		US Army
			USASC / University of Michigan	Suborbital	Aeronomy	8 June	Launch failure
		Apogee: 6.4 kilometres (4.0 mi), full burn but very low thrust
9 June 06:11	Aerobee XASR-SC-1		SC 18	White Sands LC-35		US Army
		Grenades	USASC	Suborbital	Aeronomy	9 June	Successful
		Apogee: 66.8 kilometres (41.5 mi)
13 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	13 June	Successful
14 June 13:48	V-2		V-2 No. 55	White Sands LC-33		GE / US Army
			NRL	Suborbital	Cosmic Radiation / Solar UV / Solar X-Ray	14 June	Launch failure
		Project Hermes launch, apogee: 0 kilometres (0 mi), rocket exploded at ignition
14 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	14 June	Successful
18 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	18 June	Successful
19 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	19 June	Successful
20 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	20 June	Successful
22 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	22 June	Successful
23 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	23 June	Successful
24 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	24 June	Successful
25 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	25 June	Successful
26 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	26 June	Successful
27 June	R-1			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	27 June	Successful
28 June 21:43	V-2		V-2 No. 52	White Sands LC-33		GE / US Army
		Blossom IVF	Air Materiel Command	Suborbital	Solar UV / Solar X-Ray / Ionospheric / Photography / Aeronomy / Biological	28 June	Launch failure
		Final project Hermes launch, apogee: 5.8 kilometres (3.6 mi), explosion in tail section at 8 seconds, cutoff triggered at 22 seconds

July launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
2 July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	2 July
		First of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Second of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Third of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Fourth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Fifth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Sixth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Seventh of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Eighth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Ninth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Tenth of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Eleventh of thirteen launches, 12 of which hit the target area.
July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	Same day
		Twelfth of thirteen launches, 12 of which hit the target area.
22 July	R-1V			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Biological	22 July	Successful
		Maiden flight of the R-1V; first ever space dog mission carried dogs Dezik and Zhegan which were recovered.
25 July 16:26	Aerobee RTV-A-1		USAF 15	Holloman LC-A		US Air Force
			AFCRC	Suborbital	Sky Brightness	25 July	Successful
		Apogee: 71.3 kilometres (44.3 mi)
27 July	R-2			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Missile test	27 July
		Last of thirteen launches, 12 of which hit the target area.
29 July	R-1B			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Biological	29 July	Launch failure
		Maiden flight of the R-1B; electrical failure, no payload recovery; carried dogs did not survive

August launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
7 August 16:36	Aerobee RTV-A-1		USAF 16	Holloman LC-A		US Air Force
			AFCRC / Boston University	Suborbital	Ionospheric	7 August	Successful
		Apogee: 83.5 kilometres (51.9 mi)
7 August 18:00	Viking (first model)			White Sands LC-33 – Army Launch Area 1		US Navy
		Viking 7	NRL	Suborbital	Cosmic Radiation / Solar X-Ray / Aeronomy	7 August	Successful
		Final flight of the first model Viking, apogee: 219 kilometres (136 mi)
15 August	R-1B			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Solar UV / Biological	15 August	Successful
		Carried dogs, recovered
19 August	R-1V			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Biological	19 August	Successful
		Final flight of the R-1V; carried dogs, recovered
22 August 19:00	V-2		TF-1	White Sands LC-33		US Army
			US Army	Suborbital	Altitude test	22 August	Successful
		First all Army team after General Electric's contract concluded; apogee: 213.4 kilometres (132.6 mi)
28 August	R-1B			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Biological	28 August	Successful
30 August 22:40	Aerobee RTV-A-1b		USAF 17	Holloman LC-A		US Air Force
			AFCRC	Suborbital	Rocket test	30 August	Successful
		Maiden (and only) flight of the RTV-A-1b, apogee: 76 kilometres (47 mi)

September launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
3 September	R-1B			Kapustin Yar		OKB-1
			OKB-1	Suborbital	Biological	3 September	Successful
		Final flight of the R-1B; carried dogs, recovered
13 September 11:37	Aerobee RTV-A-1		USAF 18	Holloman LC-A		US Air Force
			AFCRC / University of Michigan	Suborbital	Aeronomy	13 September	Successful
		Apogee: 76 kilometres (47 mi)
20 September 16:31	Aerobee RTV-A-1		USAF 19	Holloman LC-A		US Air Force
		Aeromed 2	AFCRC / WADC Aero-Medical Laboratory	Suborbital	Biological	20 September	Successful
		Carried monkey, Yorick/Albert VI, and 11 mice, all recovered; apogee: 71 kilometres (44 mi)
27 September 00:06	Aerobee XASR-SC-1		SC 21	White Sands LC-35		US Army
			USASC / University of Michigan	Suborbital	Aeronomy	27 September	Successful
		Apogee: 68.9 kilometres (42.8 mi)

October launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
17 October 18:17	Aerobee RTV-A-1a		USAF 20	Holloman LC-A		US Air Force
			AFCRC / Boston University	Suborbital	Ionospheric	17 October	Successful
		Apogee: 114.3 kilometres (71.0 mi), maiden flight of the RTV-A-1a
29 October 21:04	V-2		V-2 No. 60	White Sands LC-33		US Army
			USASC / University of Michigan	Suborbital	Aeronomy	29 October	Successful
		Apogee: 141.0 kilometres (87.6 mi)

November launches

Date and time (UTC)	Rocket		Flight number	Launch site		LSP
		Payload	Operator	Orbit	Function	Decay (UTC)	Outcome
		Remarks
1 November 09:46	Aerobee XASR-SC-1		SC 20	White Sands LC-35		US Army
		Grenades	USASC	Suborbital	Aeronomy	1 November	Successful
		Apogee: 66.3 kilometres (41.2 mi)
3 November 00:35	Aerobee XASR-SC-1		SC 22	White Sands LC-35		US Army
		Grenades	USASC	Suborbital	Aeronomy	3 November	Successful
		Apogee: 82 kilometres (51 mi)

← Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec →

Launches by country

Country		Launches	Successes	Failures	Partial failures
	United States	26	19	6	1
	Soviet Union	35	33	1	1

Launches by rocket

Rocket	Country	Launches	Successes	Failures	Partial failures	Remarks
V-2	United States	6	2	4	0
Viking (first model)	United States	1	1	0	0	Retired
Aerobee RTV-N-10	United States	3	3	0	0
Aerobee XASR-SC-1	United States	5	4	1	0
Aerobee RTV-A-1	United States	9	7	1	1
Aerobee RTV-A-1b	United States	1	1	0	0	Maiden flight, retired
Aerobee RTV-A-1a	United States	1	1	0	0	Maiden flight
R-1	Soviet Union	16	16	0	0
R-1V	Soviet Union	2	2	0	0	Maiden flight, retired
R-1B	Soviet Union	4	3	1	0	Maiden flight, retired
R-2	Soviet Union	13	12	0	1

• Timeline of spaceflight