NASA Project Gemini - Launch Vehicles/Rockets

For Project Gemini, NASA again used modified military ICBMs to reach space, just as they had done for Project Mercury. The newer, more powerful Titan II missile, developed by the US Air Force for the deployment of nuclear warheads, carried the 2-man Gemini capsule into orbit. The unmanned Agena Target Vehicle (which was used as a target for rendezvous and docking maneuvers) was launched atop an Atlas booster.

A Titan II rocket launches the manned Gemini capsule into orbit. Photo courtesy of NASA.
A Titan II rocket launches the manned Gemini capsule into orbit. Photo courtesy of NASA.

Titan II

The 2-stage Titan II was the first multi-stage rocket used by the US for manned spaceflight. A multi-stage rocket consists of separate sections, or stages, stacked atop one another, each with its own engine and fuel supply. When the fuel from one stage is exhausted, that stage drops off and falls away from the rocket, and the next stage's engine is ignited.

Trade-offs of Rocket Staging

The primary benefit of rocket staging is that an ascending rocket becomes lighter as it discards the unneeded weight of emptied fuel tanks. The remaining fuel can then push the less massive rocket faster and further. This, of course, adds to the complexity (and cost) of the rocket. It also increases the risk associated with a launch, as there is a possibility that a stage's engine will fail to ignite. Gemini required a multi-stage rocket, however, due to the weight of the Gemini spacecraft, which otherwise could not have been accelerated to orbital velocity.

Video: Camera aboard Titan II shows separation of first stage:

Gemini-Titan

Modifications made to the Titan II missile for Project Gemini included the addition of a system to detect and notify the crew of malfunctions, and an inertial guidance system (Titan was radio-controlled when used as an ICBM). Certain system redundancies were added for safety, and elements of the missile that were not needed for Gemini flights were removed.

Between April, 1964 and November, 1966, twelve Gemini-Titan missions were launched. Two were unmanned test launches, and ten were manned missions. All were successful. Gemini-Titan launches took place at Cape Canaveral, Florida (then known as Cape Kennedy), from Launch Complex 19.

Atlas-Agena

One of the primary objectives of Project Gemini was the development of rendezvous and docking techniques. NASA needed to master these techniques to have any hope of achieving President Kennedy's goal of a lunar landing within the decade.

Docking

Docking is a procedure in which two spacecraft are physically linked together. In some cases, the electrical systems of the two craft are connected while docked. When docked to the Agena Target Vehicle, for example, the Gemini astronauts could fire the Agena's engine using controls within the Gemini capsule.

The Agena Target Vehicle was developed for this purpose. This unmanned vehicle would be launched separately, and the Gemini astronauts would attempt first to rendezvous with the Agena target, and then dock with it.

Atlas, the US Air Force booster used on all Project Mercury orbital missions, was used to launch the Agena Target Vehicle. All Atlas-Agena launches for Project Gemini took place at Cape Canaveral's Launch Complex 14, the same site as the orbital Mercury-Atlas launches.

The Agena Target Vehicle is launched using an Atlas booster. Phot courtesy of NASA.
The Agena Target Vehicle is launched using an Atlas booster. Phot courtesy of NASA.

Stage-and-a-half Configuration

Atlas was not a multi-stage rocket, although it did have two smaller rocket engines attached to the sides of the main engine.These engines ignited at liftoff, along with the main engine, and were jettisoned when their fuel was expended.

These engines were not true rocket stages, because they ignited at launch, rather than during flight following the shut off of another engine. This configuration is sometimes known as a stage-and-half configuration.

Titan and Atlas continued to be workhorses for NASA for many years following Project Gemini. Titan and Atlas-based launch vehicles have put numerous satellites into earth orbit, and have launched several unmanned probes to other parts of the solar system - and beyond, in the cases of the Pioneer and Voyager probes.

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Comments 8 comments

sean kinn profile image

sean kinn 5 years ago from Key West and Budapest

GD, I've been meaning to write a Hub about NASA's X-37B project, but haven't found the time yet. I guess I'm impressed with whatever it is they're trying to hide, since the Shuttle program has ended. :-) I love your NASA Hubs, keep up the good work. Sean


GD Nunes profile image

GD Nunes 5 years ago from Cape Cod, USA Author

Thanks, Sean. I'd love to read your hub on the X-37B if you ever find the time to finish it. I would very much like to know more about that project, as well. I could be wrong, but I thought the X-37 program was transferred from NASA to the US Air Force a few years ago. That would explain the secrecy, as NASA tends to be more open about their programs.


sean kinn profile image

sean kinn 5 years ago from Key West and Budapest

I think you're right about it being an Air Force program now. One of the things that interests me about the program as a whole is that we appear to be relatively weak right now. If we need to put a man in space, we have to rely on Russia, right? So I'm wondering how much robotics is contained in the X-37B to replace our highly trained astronauts, since they did so much work outside in space. Just thinking out loud ... :-)


GD Nunes profile image

GD Nunes 5 years ago from Cape Cod, USA Author

Yes, Americans going into space will have to hitch a ride on Russia's Soyuz spacecraft for several years (no one knows how many years. SpaceX says their Dragon spacecraft could be man-ready in 2014, so that's the earliest our dependence on Russia could end - if all goes well). How did we get to this point? Budget cuts for NASA may have something to do with it, but some really bad long-range planning is also to blame.


sean kinn profile image

sean kinn 5 years ago from Key West and Budapest

In my experience, there is always a Rest of the Story. Which is why I continue to wonder about the X-37B and all other secret or open space programs we have. NASA folk are pretty serious about space exploration, so I just can't imagine they would let rinky-dink politicians stand in their way. :-)


GD Nunes profile image

GD Nunes 5 years ago from Cape Cod, USA Author

Yes, there's undoubtedly always more going on than what we hear about. I'd love to get a look at some of those things as well.


Richard Barry 21 months ago

takes me back a few years. I was on the Pad Activation team for the first Titan Gemini, then to Titan IIIA, IIIC and IIID. Great history, fantastic launch record and historical teams. Thanks for the memories.


GD Nunes profile image

GD Nunes 20 months ago from Cape Cod, USA Author

Thanks Richard! You folks did great work!

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