Dealing with gravity in space launches is not an easy task. Conventional rockets are very expensive, generate a lot of debris and, in practice, are very dangerous. Fortunately, science does not stand still, and more and more alternative ways appear that promise us more efficient, less costly and safer ways to conquer outer space. Today we will talk about how humanity will fly into space in the future.
But before we start, it should be pointed out that chemical jet engines (CRM), which are now used as the basis for all space launches, are a critical tool for the development of the space sector, so their use will continue for several decades until found and, most importantly, repeatedly tested a technology capable of providing a painless transition to a fundamentally new level of space launches and flights.
But already now, when the cost of launches can amount to several hundred million dollars, it becomes clear that the HRD is a dead end. Take the latest Space Launch System as an example. It is this system that is considered by the NASA aerospace agency as the basis for deep space exploration. Experts have calculated that the cost of one launch of SLS will be about $ 500 million. Now that space has become not only a matter of states but also of private companies, cheaper alternatives have begun to be offered. For example, SpaceX's Falcon Heavy will cost around $ 83 million to launch. But it's still very, very expensive. And we do not yet touch upon the issue of environmental friendliness of space launches based on the CRD, which, without a doubt, cause significant harm to the environment.
The good news is that scientists and engineers are already proposing alternative ways and methods of space launches, and some of them do have the potential to become effective technologies over the next decades. All these alternatives can be summarized under several categories: alternative types of jet launches, stationary and dynamic transport systems, and ejection systems. Of course, they do not unite all the proposed ideas, but in this article we will analyze the most promising ones.
Alternative types of jet launches
Laser jet thrust
Plasma flow redirection to increase thrust
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The missiles in use today require huge amounts of solid or liquid propellants, and most often their range and effectiveness are limited by how much of that fuel they can carry. However, there is an option that will overcome these limitations in the future. The solution may be special laser installations that will send rockets into space.
Russian physicists Yuri Rezunkov of the Institute for the Development of Optoelectronic Instruments and Alexander Schmidt of the Ioffe Physicotechnical Institute recently described the process of "laser ablation", according to which the thrust of an aircraft would be generated using laser radiation generated by a laser device outside the spacecraft. As a result of exposure to this radiation, the material of the receiving surface will be burned and a plasma flow will be created. This flow will provide the necessary thrust capable of accelerating the spacecraft to speeds tens of times greater than the speed of sound.
If we omit all the fantastic nature of this method, before creating such a system, it will be necessary to solve two problems: the laser in this case must be incredibly powerful. So powerful that it can literally vaporize metal over a distance of several hundred kilometers. Hence another problem - this laser can be used as a weapon to destroy other spacecraft.
Stratospheric launches and space planes
Less conceptual and more realistic seems to be the method of launching spacecraft with the help of special powerful load-carrying air tractors.
Who said that Virgin Galactic's method could only be used for space tourism? The company plans to use its LauncherOne device as a transportation system to launch compact satellites weighing up to 100 kilograms into Earth's orbit. Considering the speed with which space systems are miniaturized now, the idea is very interesting.
Other examples of a launch system are the XCOR Aerospace Lynx Mark III spacecraft (pictured above) and the Orbital Sciences Pegasus II spacecraft (pictured below).
One of the advantages of space launches from airspace is that rockets do not have to travel through a very dense atmosphere. As a result, the load on the device itself will decrease. In addition, the aircraft is much easier to start. It is less susceptible to atmospheric weather changes. In the end, the feature of such launches opens up more possibilities in terms of the selectable scale.
Space planes are another option. These reusable aircraft will be similar to the retired shuttle and Buran, but, unlike the latter, will not require the use of huge launch vehicles for launch into orbit. One of the most promising and advanced projects in this regard is the British spaceplane British Skylon (pictured above) - a single-stage aircraft for entering orbit. The spacecraft's jet thrust will be generated by two air-jet engines, which will accelerate it to a speed 5 times higher than the speed of sound and lift it to an altitude of almost 30 kilometers. However, this is only 20 percent of the required speed and altitude required for spacewalk, so the spaceplane will switch to the so-called "rocket mode" after reaching the altitude ceiling.
Unfortunately, there are still many technological difficulties on the way to the implementation of this project that have yet to be resolved. For example, spaceplanes are expected to face an unplanned change in their ascent trajectory due to high dynamic pressures and extreme temperatures that will inevitably affect the most sensitive parts of the aircraft. In other words, such spaceplanes can be dangerous.
Another example of spaceplanes under development is the Dream Chaser, developed by the Sierra Nevada Corporation for NASA's aerospace agency (pictured above).
Stationary and dynamic transport systems
If not flying machines, then huge structures that rise to incredible heights or even straight into space are the solution.
For example, Geoffrey Landis, a scientist and science fiction writer, proposed the idea of building a giant tower, whose top would reach the limits of the earth's atmosphere. Located about 100 kilometers above the Earth's surface, it can be used as a launch platform for conventional rockets. At this altitude, rockets practically do not have to deal with any impact of the earth's atmosphere.
Another construction option that has attracted the attention of many representatives of the scientific and pseudo-scientific communities is the space elevator. In fact, this idea dates back to the 19th century. The modern version proposes to stretch a heavy-duty cable to an altitude of 35 400 (which is outside the location of most communication satellites) kilometers above the Earth's surface. After carrying out all the necessary balancing on the cable, it is proposed to start up the transport vehicles operating on laser traction with a load.
Illustration of a space elevator on Mars
The idea of space elevators does indeed have the potential to create a real revolution in space transportation to near-earth orbit. But it will be very difficult to translate this idea into real life. It will take a long time before scientists create a material that can support the weight of such a structure. The options under consideration are now carbon nanotubes, or rather, structures based on microscopic diamond interlacements with ultra-thin nanofibers. But even if we find a way to build a space elevator, it won't solve all the problems. Dangerous vibrations, intense vibrations, collisions with satellites and space debris are just a few of the tasks that will have to be dealt with.
Another proposed alternative is giant "orbital flywheels". Flywheels are rotating satellites with long ropes diverging in two different directions, the ends of which will touch the planet's atmosphere during rotation. In this case, the rotation speed of the structure will partially or completely compensate for the orbital speed.
The Orion's Arm portal explains how they work:
“On the lower part of the cable, located near a planet the size of the Earth, there will be a docking platform at an altitude of 100-300 kilometers above the surface (while the very length of the cables from the center of the flywheel will be several thousand kilometers). This height was chosen because here the effect of the atmosphere on the "flywheel" itself will be minimized, as well as the gravitational losses of the docking shuttles will be minimized. Docking will occur at very low speeds of both the flywheel itself and the docking shuttle, usually at the peak of the parabolic suborbital trajectory set by the launch vehicle. In this case, the shuttle will be relatively motionless relative to the "flywheel" and can be caught by a special hook and then pulled to the docking lock or landing platform. For correct positioning in orbit, the "flywheels" will use thrusters."
Since the flywheels will be located entirely in space, not anchored to the Earth, they will not have to experience the same physical stress as the space elevator, so this idea may ultimately prove to be more viable.
When it comes to dynamic structures, Popular Mechanics describes at least two main options:
“Structures such as the 'space fountain' and 'Lofstrom's loop' will maintain their structural integrity due to electrodynamic effects or impulses moving parts inside them, as well as cargo and passengers going into orbit. Rotovators seem to be a more interesting concept. This idea proposes the construction of a large orbital structure with a tether rotating in the plane of the orbit so that at the point of the circle closest to the Earth, the speed of the end of the tether relative to the center is opposite to the orbital speed. Thus, the cable, passing the minimum, can pick up the desired object, which has a speed lower than the first cosmic one, and release it at the point of maximum distance with a speed that is already greater than the first cosmic one”.
It will look something like the "gif"
Another alternative to the space cable and elevator is a vertical inflatable tower that can grow 20-200 kilometers in height. The design proposed by Brendan Quinn and his colleagues will be erected on the top of the mountain and will be perfect for atmospheric research, installation of television and radio communications equipment, spacecraft launches and tourism. The tower itself will be created on the basis of several pneumatic externally controlled sliding sections.
“Choosing a tower will help avoid the problems associated with the space elevator. It is about the strength of a building material suitable for work in space, the difficulty of producing a cable at least 50,000 kilometers long and addressing the meteorite threat in low Earth orbit,”said the researchers who proposed the tower design.
To test their idea, they built a 7-meter tower model with six modules, each of which was based on three tubes installed around a cylindrical compartment filled with air.
Interestingly, a similar technology can be used in the construction of the "space pier" proposed by John Storrs Hall. According to this concept, it is proposed to build a structure 100 kilometers high and 300 kilometers long. With this setup, the elevator will move directly to the launch point. The very launch of the payload into orbit will occur with an acceleration of only 10g.
“This hybrid option ignores the disadvantages of the proposed options with an orbital tower (the size of the pier is much smaller, therefore, it is easier to build) and the difficulties that will have to be faced with electromagnetic launches (the density and resistance of air at an altitude of 100 kilometers is a million times less than at the level sea),”says Hall.
Catapult systems
If all the proposed ideas for the average reader may seem quite science fiction, then the following ones are much closer to reality than they might seem at first glance. Another alternative to rocket launches is catapult systems, in which spacecraft will be launched into space like a cannon.
It is quite obvious that in this case the load itself will have to be designed for the impact of extreme forces. However, catapult systems can become a really effective tool for sending a payload into space, where it will be picked up by spacecraft located there.
Catapult systems can be divided into three main types: electrical, chemical, and mechanical.
Electrical
This type includes railguns, or electromagnetic catapults, operating on the principle of electromagnetic accelerators. During launch, the spacecraft will be placed on special guide rails and accelerated sharply using a magnetic field. In this case, the force of acceleration will be sufficient in order to bring the device out of the earth's atmosphere.
However, the design feature of such systems will make them very massive and expensive to build. In addition, such systems will consume a huge amount of electricity. Despite their power, electromagnetic catapults will still have to face some of the problems associated with gravity and Earth's dense atmosphere. If they are used, it is more likely on planets with lower gravity and a rarefied atmosphere.
Chemical
It proposes launching objects into space using huge guns fueled by a combustible gas like hydrogen. However, as with any ejection system, the cargo sent into space will have to experience increased loads during launch. In addition, such systems cannot be used to send people into space. In addition, additional equipment would have to be used that would allow launching cargo, such as compact satellites, into permanent orbit. Otherwise, the launched object, having gained maximum altitude, will simply fall back to Earth.
HARP Project (High Altitude Research Project). This cannon fired a Martlet-2 rocket projectile to an altitude of 180 kilometers. The record is still held
The logical development of the HARP project was the SHARP project (Super High Altitude Research Project). In the 90s of the last century, researchers from the Lawrence Livermore Lab conducted a demonstration of the launch of projectiles at a speed of 3 kilometers per second (although not in height, but on the ground). In the end, scientists came to the conclusion that the construction of a real working sample of such a weapon would require at least $ 1 billion. The picture was also thickened by the fact that the scientists failed to achieve the planned projectile speed of 7 kilometers per second.
Mechanical
Mechanical guns can serve as an alternative to electromagnetic and chemical guns. True, it is not entirely correct to call such systems guns. Rather, it is a kind of slingshot. An example is HyperV Technologies Corp.'s Slingatron project. The system itself is a spiral hollow structure inside. An object placed inside the spiral is accelerated by rotating the entire structure around a fixed point.
In theory, the slingatron is capable of providing the necessary acceleration. However, as the developers themselves point out, the system is not suitable for launching people and large loads into orbit. But this method could be used to send small loads into space, such as water supplies, fuel and building materials.
A full-size view of the slingatron would look something like this
What will the future really be like?
It is extremely difficult to predict what the answer to this question will be. Unexpected technological discoveries and the effects created by them may lead to the fact that all the options for rocketless space launches considered today will become on a par with efficiency. Now this is not the case, as can be seen at least from the comparative table here.
Take the potential of molecular assembly technology as an example. Once we master this area, we no longer need to launch anything into space. We will simply catch asteroids in the solar system and create from them (or rather the useful materials contained in them) whatever we want right in space. The most interesting thing is that progress in this direction is already visible today. For example, NASA astronaut Barry Wilmore once needed a compact adjustable wrench. It would seem, what's the problem - going to the nearest tool store? Only the nearest tool store at that time was not next to Wilmore, since the astronaut was on board the International Space Station!NASA got out of the situation gracefully - it sent an e-mail to the ISS a diagram of the required key and offered Wilmore to print it himself on a 3D printer on board. This is just one example showing that in a relatively short time we will not need to launch anything into space at all. Everything will be created already in place.
As for the necessary resources, then this will also cease to be a problem. The asteroid belt is full of the necessary material: its volume is almost half the mass of our Moon. Someday we will come to the conclusion that a whole swarm of "Philae" -like space probes will simply land on the next asteroid or meteorite and produce mineral resources on them. NASA wants to conduct the first such mission in 2020. It is planned to catch a small asteroid, put it into a stable lunar orbit, and there to land astronauts on it, who can study the space cobblestone and even collect interesting samples of its soil.
Getting people into space is a different problem, especially when you consider that in the future there are plans to move to mass sending people into space. Some of the proposed ideas, like the space elevator, might actually work. But only if we are not talking about the conquest of deep space. Therefore, in this matter we will have to rely on traditional rocket launches for a long time. Their ideas are already being voiced both at the state level and in the private sphere. Take again the same Elon Musk with his Mars colonization project.
We also have to take into account the fact that the human body is not really designed for a very long stay in space. Therefore, until we come to effective technologies that allow creating artificial gravity, robots can become a partial solution to this problem. Robots can be sent into space and remotely controlled from Earth using augmented or virtual reality.
Robots have a real chance to be the key to starting our deep space exploration. It is quite possible that in the more distant future we will learn how to digitize our brains and transmit this information to supercomputers on board remote space stations, where it will be loaded into a variety of robotic avatars, with which we will pave our way to the distant frontiers of space.
NIKOLAY KHIZHNYAK