Bussard ramjet designs that use the collected hydrogen only as reaction mass are sometimes referred to as ram-augmented interplanetary or interstellar rockets ( RAIR ) to distinguish them from the designs that use the collected hydrogen as fuel.

Beta thus effectively functions as a ramjet in the lower atmosphere and thus must be launched using an electric launch track.

In practice, since the force of drag produced by collecting the interstellar medium increases approximately as its speed squared at non-relativistic speeds and asymptotically tends to infinity as it approaches the speed of light ( taking all measurements from the ship's perspective ), any such ramjet would have a limiting speed where the drag equals thrust.

If a ramjet could accelerate at 10 m / s < sup > 2 </ sup >, slightly more than one Earth gravity, it would attain 77 % of light velocity within a year.

The collection-radius of such an ionic ramscoop is the distance from the ramjet at which the ramscoop's electric field is greater than the galactic electric field of 1. 6 × 10 < sup >− 19 </ sup > V / m, or the ramscoop's electromagnetic field is greater than the natural galactic magnetic field of 0. 1 nanotesla ( 1 × 10 < sup >− 6 </ sup > gauss ).

However Daniel P. Whitmire's 1975 analysis indicates that a ramjet may achieve net power via the CNO cycle, which produces fusion at a much higher rate (~ 10 < sup > 16 </ sup > times higher ) than the proton-proton chain.

* d / dt ( mv < sub > 2 </ sub >) is the thrust produced by the ramjet ; d / dt ( mv < sub > 2 </ sub >) is the mass of the collected ramjet propellant per unit time multiplied by the exhaust velocity at which it is expelled from the Ramjet engine to generate thrust.

For example, a ramjet might collect 1 gram of incoming ions per second from interstellar space beyond the heliopause, at a velocity of 50 km / s relative to the ramjet driven spacecraft.

* Although the pre-launching fuel for the ramjet negates one advantage of the Bussard design ( collection of fuel as it moves through the interstellar medium ) it retains the advantage of not having to accelerate the mass of the fuel and the mass of the rocket at the same time.

The principle behind the nuclear ramjet was relatively simple: motion of the vehicle pushed air in through the front of the vehicle ( ram effect ), a nuclear reactor heated the air, and then the hot air expanded at high speed out through a nozzle at the back, providing thrust.

They represent a hybrid class of rocket / ramjet engines, similar to a ramjet, but able to give useful thrust from zero speed, and are also able in some cases to operate outside the atmosphere, with fuel efficiency not worse than both a comparable ramjet or rocket at every point.

Another advantage is that the rocket works even at zero forward speed, whereas a ramjet requires forward motion to feed air into the engine.

The slow pace of Russia's ramjet powered R-77 derivative, a mock-up of which had been displayed at the Paris Air Show but which had not progressed past component ground tests and for which the Russian air force had no requirement due to lack of funding, was offered as evidence that the full capability required by SR ( A ) 1239 would not be necessary for some time.

It then transitions to ramjet propulsion at near-supersonic speeds, then to supersonic combustion or scramjet propulsion, above Mach 6, then back to pure rocket propulsion above Mach 10.

A jet engine afterburner is an extended exhaust section containing extra fuel injectors, and since the jet engine upstream ( i. e., before the turbine ) will use little of the oxygen it ingests, the afterburner is, at its simplest, a type of ramjet.

Early problems were ironed out and the JTV series was the first British ramjet powered aircraft to operate continually at supersonic speeds.

The afterburner behind a turbine runs with a stoichiometric mixture like a ramjet but at higher pressure and thus more efficiency than a pure ramjet.

This allows ramjet combustors to burn at a higher temperature.

The ATREX engine ( Air Turbo Ramjet Engine with eXpander cycle ) developed in Japan is an experimental precooled jet engine that works as a turbojet at low speeds and a ramjet up to mach 6. 0.

The scramjet had first been outlined at about the same time as the original LACES design in a NASA paper of 1958, and many companies were highly interested in seeing it develop, perhaps none more than Marquardt, whose ramjet business was dwindling with the introduction of newer jet engines and who had already started work on the scramjet.

Jet engines take a large volume of hot gas from a combustion process ( typically a gas turbine, but rocket forms of jet propulsion often use solid or liquid propellants, and ramjet forms also lack the gas turbine ) and feed it through a nozzle that accelerates the jet to high speed.

They calculated that the trip would take several hundred years and that the ship would have to withstand gravity accelerations of 60 g. They wrote several papers on that and other proposed methods of space travel, such as laser propulsion, the Bussard ramjet, and exotic fuels that could give very high power.

Unlike ramjet or scramjet engines the design is able to provide high thrust from zero speed up to Mach 5. 5, with excellent thrust over the entire flight, from the ground to very high altitude, with high efficiency throughout.

The Hughes / Raytheon design was largely based on the ACIMD missile, with a hybrid ramjet / solid rocket engine which offered high speeds.

This distinguishes the system from a turboramjet where a turbine-cycle ’ s exhaust is used to increase air-flow for the ramjet to become efficient enough to take over the role of primary propulsion.

Simple ramjet operation, with Mach numbers of flow shown

The Lockheed D-21 was a Mach 3 + reconnaissance drone that was powered with a ramjet which was launched from a parent aircraft such as the Lockheed A-12.

The booster motors accelerate the missile to past Mach 1. 8 and the kerosene-fuelled ramjet engines accelerate the missile to a cruise speed of Mach 2. 0.

* Republic XF-103 Thunderwarrior ( 1950s ) single-seat interceptor / fighter aircraft, with a turbojet and ramjet engines giving a projected maximum speed of Mach 3.

The scram cannon uses a projectile that uses supersonic combustion ramjet technology to increase the muzzle velocity to levels that are impossible with normal gunpowder based guns ; firearms are limited by the speed of sound in the propellant gases, which limits the velocities to about Mach 5 ( see internal ballistics ).

Included were LACES and ACES engines, as well scramjets, turboramjets and a " normal " ( subsonic combustion ) ramjet with an intake suitable for use up to Mach 8.

A replacement for Blue Steel, the Mark 2, was planned with increased range and a ramjet engine, but was cancelled in 1960 to minimise delays to the Mk. 1.

However, if the ramjet has an average acceleration of 0. 1 m / s < sup > 2 </ sup >, then it needs 100 years to go as fast, and so on.

Heppenheimer analysed Bussard's original suggestion of fusing protons, but found the bremsstrahlung losses from compressing protons to fusion densities was greater than the power that could be produced by a factor of about 1 billion, thus indicating that the proposed version of the Bussard ramjet was infeasible.

In the Zubrin / Andrews interplanetary ramjet design, they calculated that the drag force d / dt ( mv < sub > 1 </ sub >) equals the mass of the scooped ions collected per second multiplied by the velocity of the scooped ions within the solar system relative to the ramscoop.

* d / dt ( mv < sub > 1 </ sub >) is the drag force experienced by the ramjet during its actual operation ; d / dt ( mv < sub > 1 </ sub >) is the mass of collected propellant per unit time times the velocity of the scooped ions relative to the ramjet starship.

If the exhaust velocity of the ramjet were 1, 000, 000 m / s then d / dt ( mv < sub > 2 </ sub >)

A conventional Bussard ramjet will mostly collect hydrogen with an atomic weight of 1.

On January 1, 1957, the U. S. Air Force and the U. S. Atomic Energy Commission selected the Lawrence Livermore National Laboratory's ( LLNL ) predecessor, the Lawrence Radiation Laboratory, to study the feasibility of applying heat from nuclear reactors to ramjet engines.

* Bristol Thor, ramjet engine used on the Bristol Bloodhound missile

As the 1220 required long range, Bristol made the decision early on to use a ramjet for power.

** Main: 2 × Bristol Thor ramjet engines

* Bristol Odin, a ramjet engine for the British Sea Dart missile