Hypersonic Planes

• Concept Led By: N/A
• Companies Involved: Lockheed Martin, Boeing, Northrop Grumman, General Electric, Airbus, & More

During the 1960s and 1970s, several companies and engineers proposed plans to NASA and other space agencies to make spacecraft designs using hypersonic planes. Of course, a hypersonic plane is anything that can reach or surpass Mach-5. Basically, they move faster or at the speed of sound. Yet early hypersonic planes were not exactly useful and were often dealing with several technical limitations at the time. Safety concerns were so high that most space agencies, especially NASA, refused to consider anything utilizing hypersonic plane concepts.

Why do we consider hypersonic planes for spacecraft designs? Early on, these planes were able to go above the clouds and reach near-space boundaries. The notable boundary here is called the Kármán line, which planes are unable to cross because they use engines that burn air. There is no oxygen in space, so hypersonic plane designs could never take us to real space. However, this is likely to change soon. Two experimental planes (SpaceShipOne and North American X-15) use rocket engines rather than jet engines, allowing them to burn liquid fuel instead of air. We will likely be seeing these in use before too long.

Titan Mare Explorer (TiME)

• Concept Led By: N/A
• Companies Involved: Proxey Research

It needs to be highlighted that the Titan Mare Explorer, also known as TiME, is not a completely dead concept. Simply put, sometimes spacecraft designs are good ideas but the proposals are made too early. Proposed back in 2009 by Proxey Research, it was designed to be part of NASA’s Discovery Program. TiME is a lander specifically made to use for Saturn’s notable moon, Titan. The entire goal of the TiME craft is to be used to measure the “organic constituents” on Titan and perform the very first nautical exploration of an extraterrestrial sea. It would analyze the nature of Titan and even observe the shoreline.

Discovery-class missions at the time were given a hard cap of roughly $425 million, which didn’t count the launch vehicle. Since it was literally made to use for a program where this exact concept was useful, it made sense to go with it. NASA even liked the idea, which is why the TiME mission design reached the finalist stage during the Discovery mission selection process. It did not get picked and the United States Senate never marked it for funding even up to 2013. While the TiME spacecraft was useful, a Titan submarine was later proposed. Thus, the Titan Mare Explorer might never make it into space.

Project Orion

• Concept Led By: NASA, DARPA, U.S. Air Force
• Companies Involved: N/A

Project Orion is probably one of the most notable on this list and for good reason. It should be noted that this did not involve a single spacecraft but rather, a spacecraft concept. The study was conducted sometime between the 1950s and 1960s by DARPA, NASA, and the U.S. Air Force. The goal? To measure the efficacy of a starship that would be propelled by a series of atomic bomb explosions behind the craft. Known as nuclear pulse propulsion, looking back the idea seemed odd. Early versions of these spacecraft designs were proposed to, if you can believe it, take off from the ground. Later versions, however, only involved versions that took off only in space.

A total of 6 non-nuclear tests were conducted using these models, but the project would be abandoned. This was due to many reasons, but one of the biggest was the Partial Test Ban Treaty. This did not explicitly target spacecraft but rather, involved the treaty to stop doing random tests with nuclear technology. Yet it did involve not testing things in space because of the worry of nuclear fallout. The entire idea behind using nuclear energy to go to space was connected to a concept that came from Russian explosives expert, Nikolai Kibalchich, back in 1881. Later on, men like Robert A. Heinlein and Harmann Ganswidt independently came up with similar ideas.

Project Longshot

• Concept Led By: NASA/U.S. Naval Academy
• Companies Involved: N/A

There is perhaps no way we could ever name something better than Project Longshot. This real idea was, to put it lightly, exactly as advertised. This involved one of the more ambitious mission concepts and had one of the spacecraft designs that was already kind of “iffy.” The roughly 400 tonnes (or 441 tons) spacecraft was intended to be uncrewed and fly to not just the end of our solar system but go all the way to orbit around Alpha Centauri B. How would it be powered? Well by nuclear pulse propulsion, of course! You didn’t think this was going to be called a longshot and expect a “good” idea for propulsion, right? The concept was developed by the United States Naval Academy and NASA from 1987 to 1988.

If it was to be cleared for full development, it was going to be built at the Freedom Space Station. It was our precursor to the International Space Station, for those unaware. The biggest issue with Longshot was that it was not considering future concepts or tech. The developers only focused on their present-day tech from the late 1980s. They felt they could use a long-living nuclear fission reactor to power everything. Though only generating 300 kilowatts at first, it would then be powered by several lasers in the engine that would ignite inertial confinement fusion. While even today, this is not exactly a terrible concept, it would take forever to reach Alpha Centauri B, well beyond our lifetimes. Longshot, this surely was.

Sea Dragon

• Concept Led By: N/A
• Companies Involved: Aerojet

While some science fiction shows and films have sort of used this idea, it was never as wild as the real thing. Developed by Robert Truax while he was working at Aerojet in 1962, one of the many spacecraft designs he came up with was the now-infamous “Sea Dragon.” The idea was that a rocket would take off from the ocean. Of course, it was technically a floating rocket but still. Funny enough, while NASA did have some interest, one of the first private companies interested in space exploration was too, Todd Shipyards. Yet neither decided to bite.

At dimensions of just under 500 feet long and 75 in diameter, it would have been the largest rocket ever built. Keep in mind that this was a fully conceived concept too, unlike many of the proposals you see today. Among rockets that have been fully conceived but never built, the Sea Dragon is far and away the largest one. In terms of its payload into low Earth orbit, it was equaled only by the Interplanetary Transport System. The Sea Dragon was designed at the rough 600 tons limit, so it was understandably going to be useful for some ideas NASA had. However, the cost and also the mere idea of taking off from the sea just never made a lot of sense.

Where Do We Find This Stuff? Here Are Our Sources:

United Nations

National Aeronautics and Space Administration (NASA)

National Oceanic and Atmospheric Administration (NOAA)

Defense Advanced Research Projects Agency (DARPA)

European Space Agency (ESA)

Japan Aerospace Exploration Agency (JAXA)

British Interplanetary Society (BIS)

British Aerospace Systems (BAE)

United States Air Force (USAF)

United States Space Force (USSF)

Russian Aviation and Space Agency (RKA)

Massachusetts Institute of Technology (MIT)

Harvard University

Stanford University

Cornell University

Lockheed Martin (LM)

The Boeing Company

SpaceX

General Motors (GM)

Chrysler

Northrop Grumman

Aerojet

Rockwell International

TransAstronautics Corporation

Rolls-Royce

Smithsonian Institute

American Nuclear Society (ANS)