New space drives - dreams and reality
A "flashlight" drive, "hyperdrive", also called a "warp" after the Star Trek TV series, is science fiction, right? It turns out maybe, but NASA is working on it anyway. Recently there have been reports of an internal agency study on the feasibility of using this type of transmission. So what's really going on with these alternative drives of the future?
To begin with, it must be clarified that NASA does not build an engine that reaches and. In this study, experienced propulsion physicist Dr. Harold White of the Infinite Space Institute attempts to resolve the serious paradox of what is perhaps the most famous theoretical model for faster-than-light travel, also known as Alcubier Drive (1).
1. Visualization of the space-time fold around the warp ship - Alcubierre
The model, first proposed by theoretical physicist Miguel Alcubierre, is consistent with Einstein's theory. This works in a similar way to the well-known tablecloth and dishes trick. The KA is on the spatio-temporal tablecloth, the actuator vigorously pulls the fabric of the tablecloth under itself, and the KA in the blink of an eye finds itself in a new place in relation to the fabric. Alcubière described space-time as expanding on one side of the ship and contracting on the other, thanks in part to the use of negative energy. It is supposed to create a certain pocket in space-time, in which the spacecraft can operate outside the limits of physics known to us. The concept of negative energy is exotic, but.
The problem is not only in negative energy, but also in the fact that the direction of movement of the spacecraft in this model is arbitrary when using the propulsion device, it cannot be controlled. This is where the aforementioned Dr. White comes in, proposing a different paradigm. Instead of stationary spacecraft by activating the Alcubierre engine from a stopped position, the researcher proposes "a spacecraft that takes off from Earth and sets the initial speed of light, and then initiates a warp field." “The momentum of the field acts like a scalar factor on the initial velocity, resulting in a much higher apparent velocity,” White wrote. Thus, the direction of flight will be determined before the "hyperspace jump". In his reasoning, he also offers a method to reduce the need for energy.
White ends his argument by suggesting that Alcubière Drive it could initially be used internally without being thrown into wide interstellar spaces. Even on these smaller scales, it would already be something. At the moment it takes about three days to reach the Moon and in the best configuration about 6-8 months to Mars. This is what we get from propulsion systems based on mixing liquid hydrogen with oxygen and burning them in rockets. For some, what we are now using is not a drive, but even a crutch. Hence the search for alternatives.
A paddle to push yourself away from the universe
The other seeker is an 80-year-old retired physics professor. Jim Woodwardwho came up with the idea of using Mach's principle to propel spaceships. All matter in the Universe is closely connected, and the mass of a body is not its internal characteristic, but a consequence of its other parts. According to the Mach principle, the inertia of matter (resistance to acceleration) does not follow from the internal properties of matter, but is a measure of its interaction with the entire universe. Inertia it only happens because there is some matter left in the universe. This principle was formulated as a hypothesis by the Austrian physicist and philosopher of the XNUMXth century. Ernst Mach. This was one of Albert Einstein's inspirations for his general theory of relativity (GRT), but it ended up contradicting it.
Woodward he creates a minor for NASA prototype drive systems (2) which he himself calls MEGA Drive. They don't need fuel, just a constant supply of electricity. The most important thing in this layout piezoelectric discswhich simultaneously change their mass and energy states under the action of the supplied energy, which causes acceleration. It is based on slow acceleration, but over a very long period. A MEGA-powered spacecraft could eventually achieve close to the speed of light with a steady supply of electricity from an onboard nuclear reactor for several decades, Woodward said.
2. One of the MEGA Drive prototypes
His team uses in prototypes a stack of piezoelectric crystals with electrodes sandwiched between them, acting as kondensator. When a voltage is applied to the stack between the electrodes in the piezoelectric material, an alternating electric field is generated. This causes a change in energy density, fluctuations in energy. Piezoelectric crystals are electromechanical devices, which means that when a voltage is applied, they mechanically expand and contract depending on the sign of the voltage. According to Woodward, this causes an acceleration due to changes in the dimensions of the stack due to electromechanical effects, while at the same time causing the necessary acceleration in the location of the device located in a large gravitational field. The trick here, the researchers say, is getting the energy vibrations and mechanical vibrations to be correctly synchronized, which requires the use of two frequencies, the first and second harmonics, and this second harmonic must create a sequence.
In experimental tests, according to the publication, the prototype managed to create 20 micronewtons of thrust. Not much, so scientists talk about using many of these "engines" on one ship.
Woodward's work on his MEGA drive has been going on for over thirty years. In 2017, he received funding from NASA's Innovative Advanced Concepts program. Once funded, Woodward and his partners even developed concept open spacecraft named SSI lambdawhich contains an array of hundreds of MEGA disks. More recently, MEGA's latest transmission prototype produced significantly more thrust than all of its previous prototypes. Now there are plans to send a prototype into orbit.
However, other researchers are skeptical about this project. Mike McDonald, an aeronautical engineer at the Naval Research Laboratory in Maryland, told Wired magazine that the chances of it working were slim.
Ionic and nucleoli
Mach drivewhere the team of prof. Woodward refers to non-standard projects and is still considered exotic. There are other more "mainstream" ideas for slow acceleration. spacecraft for high speeds. First, ion accumulators (3). A series of such systems is too small to overcome the gravitational field of the Earth, that is, to take off. However, in space, the ion engine can reach speeds that no chemical rocket can achieve. chemical rockets can reach a maximum of 64 km/h. The ion thrusters are estimated to propel ships up to five times their speed. In addition, ion engines have a fuel efficiency of 000 percent, while chemical rockets have only 90 percent.
3. Satellite with ion engine
Ion thrusters have been used in NASA missions for years, incl. AT Deep space 1, that is, in the study of asteroid 9969 Braille and comet Borelli, in the Dawn mission that reached Vesta and Ceres. Ion thrusters are potentially promising for interstellar travel, but they also have limitations. Ion thrusters require electricity. Solar cells can only be used in this respect in the closer parts of the solar system. For further expeditions, other sources are needed, the most common of which are nuclear reactors.
And so we got to nuclear enginewhich is much more powerful than ion tubes alternative to chemical rockets in space. Although in the strict sense, such an idea as, for example, thermal nuclear propulsion (NTP) is still a chemical substance similar to liquid hydrogen. The fission energy produced in the reactor heated the fuel to a gaseous form and was expelled through a nozzle similar to traditional rockets. Such drives would make it possible to obtain twice as much thrust. And this means that the travel time will be halved, which, probably, no one will neglect.
Of course, if speed and time are not an issue, which may be the case in the future in tourism or even space recreation, then we should consider alternative propulsion solutions such as solar sails. Recently, such a scheme is called Lightsail 2 (4) was tested in orbit by an organization called the Planetary Society. He says rehearsals are inspiring.
So who knows if this is not one of the viable ways for some space trip. The solar wind, unlike negative energy or the Mach principle, is something settled in existence and in action, which is why cosmic sails seem more real than dreams of "superluminosity".
