Non-rocket spacelaunch

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Non-rocket spacelaunch is the idea of reaching outer space specifically from the Earth's surface predominately without the use of conventional chemical rockets, which today is the only method in use. Transportation to orbit is often the limiting factor in space endeavours. Present-day launch costs are very high — $3,000 to $25,000 per kilogram from Earth to Low Earth Orbit (LEO). To settle space, e.g. space exploration and space colonization, much cheaper launch methods are required, as well as a way to avoid serious damage to the atmosphere from the thousands, perhaps millions, of launches required.

Contents 1 Types of non-rocket spacelaunch methods 2 Comparison 3 Compressive structures 3.1 Space tower 4 Tensile structures 4.1 Skyhooks 4.1.1 Space elevator 4.1.2 Hypersonic Skyhook 4.2 Rotovators 4.2.1 Stationary Rotovators 4.2.2 Hypersonic Rotovator (HASTOL) 4.3 Endo-Atmospheric Tethers 4.3.1 KITE Launcher 5 Dynamic structures 5.1 Space fountain 5.2 Orbital ring 5.3 Launch loop 6 Projectile launchers 6.1 Mass driver 6.2 Ram Accelerator 6.3 Slingatron 6.4 Space gun 7 Spaceplanes 8 References

[edit] Types of non-rocket spacelaunch methods

Many alternatives to conventional chemical rockets have been proposed. Main of them are described in 1. Bolonkin A.A., Non-Rocket Space Launch and Flight, Elsevier, 2006, 488 pgs. 2. Bolonkin A.A., New Concepts, Ideas, and Innovations in Aerospace, Technology and Human Science, NOVA, 2008, 400 pgs. Below are only some descriptions of them.

Compressive Structures

• A space tower is simply a tower all the way up to outer space

Tensile Structures
Orbital – Synchronous a.k.a. skyhook is a tidally locked tether

• A space elevator, a.k.a. beanstalk is a stationary skyhook spanning from the surface to a point beyond geosynchronous orbit
• A hypersonic skyhook has a lower tip that captures its cargo at a hypersonic velocity providing only part of the total launch velocity

Orbital – Rotating

• A rotovator is a tether that rotates more than once per orbit such that the lower tip meets the cargo pick-up point with little or no lateral velocity
• A HASTOL has a hypersonic rotovator as part of the launch system, having a lower tip that captures its cargo at a hypersonic velocity providing only part of the total launch velocity

Endo-atmospheric

• A KITE launcher is a system that uses a tow plane and long tether to accelerate an aerodynamic body through the atmosphere to a velocity ~ Lift/Drag times the tow plane velocity. It can provide paylod, with or without the use of rockets, to either a Hypersonic Skyhook or the orbital portion of HASTOL

Dynamic Structures

• Cable space launcher [6] Ch.2, p.9-58.
• Circle launcher and space keeper [6], Ch.3, p.59-82.
• Gas tube hypersonic launcher [6], Ch.6, p.125-146.
• Earth-Moon cable transport system [6], Ch.7, p. 147-156.
• Earth-Mars cable transport system [6], Ch. 8, p.157-164.
• Centrifugel space launcher [6], Ch.10, p.187-208.
• Multi-reflex launcher [6], Ch.12, p.223-244.
• Asteroid launcher [6], Ch.11, p.209-222.
• Beam launcher [7], Ch.3.
• Electroctatic launcher [7], Ch.10.
• Levitron launcher [7], Ch.12.

• A space fountain is an elevator variant held up by a constant particle stream
• An orbital ring is an elevator variant spanning from the surface to a cable rotating around the planet
• A launch loop is a cable held at high altitude by magnetic levitation

Projectile Launchers

• A mass driver is a very long electrically driven accelerator
• A space gun is a cannon with a very long gun barrel
• A Ram accelerator is a long tube filled with a mixture of combustible gasses through which a projectile accelerates using the same thermodynamic cycle as a ramjet or scramjet
• A Slingatron is a spiral track on swing arms. It gyrates without changing orientation. Payloads surf out the spiral, accelerating to hypervelocity

Reaction Drives (Jets and Rockets)

• A spaceplane is a vehicle designed to reach into or nearly into outer space using jet propulsion and aerodynamic surfaces
• A laser launcher uses high powered lasers to heat air below a payload causing it to expand and accelerate the payload

[edit] Comparison

Comparison of Non-rocket Spacelaunch Methods
Initial Operating Condition for New Systems

Method	Estimated building cost in billion dollars	Estimated cost/kg put in GSO	Capacity metric tons per year	Possible with current technology
(Conventional rocket)		3,000 to 25,000		yes
Space tower				no
Space elevator				no
Hypersonic Skyhook	<1 [1]		30(a,b)[1]	yes
Rotovator				no
HASTOL				yes
KITE Launcher[2]				yes
Space fountain
Orbital ring	15 [3]	0.05[3]
Launch loop	10 [4]	300[4]	40,000[4]	yes
	30[4]	3[4]	6,000,000[4]	yes
Mass driver				yes
Ram accelerator				yes
Space gun		≤500		yes
Slingatron[5]				yes
Spaceplane				yes
Laser Launcher				no

(a) Requires first stage to ~5km/sec
(b) Subject to very rapid increase via bootstrapping

[edit] Compressive structures

[edit] Space tower

A space tower is a tower that would reach outer space. To fully replace rocket-power in leaving the planet, it would not only have to reach the Kármán line at 100km height, which is a common definition of outer space, but have to reach the geosynchronous orbit at approximately 36.000 km, since any object released at this height could drift away with minimal power. The concept of a structure reaching to geosynchronous orbit was first conceived by Konstantin Tsiolkovsky,^[6] who proposed a compression structure, or "Tsiolkovsky tower."

However, made of brick and stone, it would be impossible for it to reach more than 7000 feet or 2 kilometres before the bricks at the bottom were crushed by the weight.^[7]

With more advanced materials it may reach substantially higher, but far from any height of practical use, unless combined with any other method. The latter include being the base station of a space elevator, a pillar for the distal part of a mass driver or the "gun barrel" of a space gun.

There are a number of options for building space towers: rigid, inflatable, kinetic, electrostatic, electronic structures (see noted books above and references below).

[edit] Tensile structures

Tensile structures for non-rocket spacelaunch are proposals to use long, very strong cables (known as tethers) to drag a payload into, or fling it toward, space. Spaceflight using this form of spacecraft propulsion may be significantly less expensive than spaceflight using rocket engines. Tethers can also be used for changing orbit once in space.

Orbital tethers can be tidally locked (skyhooks) or rotating (rotovators). They can be designed (in theory) to pick up the payload when the payload is stationary, (has no significant lateral velocity) or when the payload is hypersonic (has a high but not orbital velocity).

Endo-atmospheric tethers can be used to transfer kinetics (energy and momentum) between large conventional aircraft (subsonic or low supersonic) or other motive force and smaller aerodynamic vehicles, propelling them to hypersonic velocities without exotic propulsion systems.

[edit] Skyhooks

Main article: Skyhook (structure)

A skyhook is a tidally locked tether, i.e., it rotates once each time it orbits around a planet or moon.

An example use of a skyhook is that a payload, launched from the ground, can be attached to the base of the skyhook, which is then carried to orbit. This means that a single stage to skyhook approach can be employed, and a high Isp drive or propellantless electromagnetic tether can be used to make up the momentum debt of the payload- or payload flow can be balanced from the moon.

[edit] Space elevator

Main article: Space elevator

A space elevator a.k.a. beanstalk is a stationary skyhook. It focuses on tensile structures (tethers) reaching from the ground to geosynchronous orbit.

The most common proposal is a tether, usually in the form of a cable or ribbon, spanning from the surface near the equator to a point beyond geosynchronous orbit. Neglecting perturbations, it would be possible to design such a tether to barely touch the ground while remaining in orbit. All proposals however have additional ballast placed at the two ends to provide stability. As the planet rotates, the inertia at the upper end of the tether counteracts gravity, and keeps the cable taut. Vehicles can then climb the tether and reach orbit without the use of rocket propulsion. Such a structure could hypothetically permit delivery of cargo and people to orbit at a fraction of the cost of launching payloads by rocket.

Current technology is not capable of manufacturing materials that are sufficiently strong and light enough to build an Earth based space elevator as the total mass of conventional materials needed to construct such a structure would be far too great. Recent proposals for a space elevator are notable in their plans to use carbon nanotube-based materials as the tensile element in the tether design, since the theoretical strength of carbon nanotubes appears great enough to make this practical.

Another difficulty includes shielding the passengers from the Van Allen belts which would require extremely heavy and comprehensive shielding to prevent significant health issues such as Cancer and may prevent manned launch for quite some time irrespective of the other issues.

Current technology may be able to support elevators in other locations in the solar system however, and other designs for space elevators exist that use current materials.

[edit] Hypersonic Skyhook

A hypersonic skyhook is a relatively short tether that reaches from just above the edge of space to its design length.

Without the two end ballasts, a space elevator would still be in geosynchronous orbit, and thus stationary relative to the ground. If that tether were to be shorter and still reach the surface, the center of gravity would need to drop also. This would cause the lower tip to have a velocity in the orbital direction. The shorter the tether is, the faster becomes the lower tip velocity. With higher tip velocity, lower material properties are needed to make a practical design but the less benefit is obtained from this method. Eventually, any such design becomes a balance between the expense of providing the velocity to the payload at pick-up and the expense of launching the mass of the tether and power plant as dictated by available materials. Also, the lower tip is raised out of the atmosphere to avoid heating problems.

A reference design was published ^[1] using materials similar to Spectra 2000 and relying on one Titan IV launch to orbit a fully functional hypersonic skyhook. To keep the tether weight within the launch capacity, a payload pick-up velocity of 5 km/s was assumed. Though the reference design was limited to an Initial Operating Condition of 1,500kg payload size, at a maximum rate of about one payload each 17 days, the prime limitation to higher capacity was power plant size. One launch of additional power plant would almost double the available power and capacity.

The problem is getting the payload to the altitude (100 km) and velocity (5 km/sec) required for pick-up.

[edit] Rotovators

A rotovator is a tether that rotates more than once each time it orbits around a planet or moon. Rotovators rotate in the same sense as they orbit such that the lower tip has a retrograde motion relative to the center of gravity.

Rotovators in almost all ways have the same benefits as skyhooks. However, due to the retrograde velocity, the lower tip can achieve a specified Mach number with a shorter tether. This, despite the rotational forces, produces lower stresses in the tether so that lower strength to weight ratio materials can be used for the same results.

[edit] Stationary Rotovators

A stationary rotovator implies only that the retrograde velocity of the tip fully cancels the orbital velocity. To a stationary payload, it appears as though the tether tip decelerates as it drops straight down from the sky, and then accelerates back upward. The payload must grapple the tip of the tether during that short duration when the tip has come to a stop.

[edit] Hypersonic Rotovator (HASTOL)

Similar to a hypersonic skyhook, a hypersonic rotovator uses a much shorter tether than its stationary equivalent and picks up its payload at hypersonic speeds. The Hypersonic Airplane, Space Tether, Orbital Launch (HASTOL) is one design for a hypersonic rotovator.

[edit] Endo-Atmospheric Tethers

An endo-atmospheric tether uses the long cable within the atmosphere to provide some or all of the velocity needed to reach orbit. The tether is used to transfer kinetics (energy and momentum) from a massive, slow end (typically a large subsonic or low supersonic aircraft) to a hypersonic end through aerodynamics or centripetal action.

[edit] KITE Launcher

The Kinetics Interchange TEther (KITE) Launcher is one proposed endo-atmospheric tether. A KITE Launcher can be single stage, achieving ~Mach 6 at release; augmented, achieving ~Mach 12 at release, or multi stage, achieving up to orbital.

[edit] Dynamic structures

[edit] Space fountain

Main article: Space fountain

A space fountain is a proposed form of space elevator that does not require the structure to be in geosynchronous orbit, and does not rely on tensile strength for support. In contrast to the original space elevator design (a tethered satellite), a space fountain is a tremendously tall tower extending up from the ground. Since such a tall tower could not support its own weight using traditional materials, massive pellets are projected upward from the bottom of the tower and redirected back down once they reach the top, so that the force of redirection holds the top of the tower aloft. Satellite payloads ascend or descend by coupling with this stream of pellets or by climbing up the side of the tower. The space fountain has several key advantages over a space elevator in that it doesn't require materials with extreme strength, can be located at any point on a planet's surface instead of just the equator, and can be raised to any height required. Its major disadvantage is that it is an active structure, and so requires constant power input to remain aloft.

[edit] Orbital ring

Main article: Orbital ring

An Orbital Ring is a concept for a space elevator that consists of a ring in low earth orbit that rotates at slightly above orbital speed, that has fixed tethers hanging down to the ground.

The first design^{[citation needed]} of orbital ring offered A. Yunitsky in 1982 ^[8]. Later the other design suggested and research A.Bolonkin in World Space Congress - 2002 [10].

In the 1982 Paul Birch JBIS design^[9] of an orbital ring system, a rotating cable is placed in a low Earth orbit, rotating at slightly faster than orbital speed. Not in orbit, but riding on this ring, supported electromagnetically on superconducting magnets, are Ring Stations that stay in one place above some designated point on Earth. Hanging down from these Ring Stations are short space elevators made from cables with high tensile strength to mass ratio. Paul Birch found that since the Ring Station can be used to accelerate the orbital ring eastwards as well as hold the tether, it is possible to deliberately cause the orbital ring to precess around Earth instead of staying fixed in inertial space while the Earth rotates beneath it. By making the precession rate large enough, the Orbital Ring can be made to precess once per day at the rate of rotation of the Earth. The ring is now "geostationary" without having to be either at the normal geostationary altitude or even in the equatorial plane. This means that using the orbital ring concept, a Ring Station can be positioned above any point on Earth that is desired, and anywhere on the globe can be served by a space elevator instead of just the equator. A network of orbital ring systems crossing, for example, at the poles, could cover the whole planet with an array of elevators and geostationary ring stations.

[edit] Launch loop

Main article: Launch loop

A launch loop or Lofstrom loop is a design for a belt based maglev orbital launch system that would be around 2000 km long and maintained at an altitude of up to 80 km (50 mi). Vehicles weighing 5 metric tons would be electromagnetically accelerated on top of the cable which forms an acceleration track, from which they would be projected into Earth orbit or even beyond.

The published cost estimates for a working launch loop are significantly lower than a space elevator, with a greater launch capacity, lower payload costs and similar or greater payload masses; and unlike the space elevator no new materials need to be developed.

However, it would constantly need around 200 MW of energy to keep it in place.

The system is designed to be suitable for launching humans for space tourism, space exploration and space colonization.

In works by Bolonkin ^[10], ^[11], ^[12] it is suggested that K. Lofstrom project has many non-solved problems and that is very far from a current technology. For example, the Lofstrom project has free (not connected) iron 1.5 meter plates. Their speeds (under gravitation, friction) can be different and they may wedge in the tube; and the force and friction in the ground 1-2 km ring are gigantic etc. In Bolonkin 2008^[13] a simple rotated close-loop cable which can launch the space apparatus which, it is claimed, is suitable for current technology.

[edit] Projectile launchers

[edit] Mass driver

Main article: Mass driver

A mass driver is basically a very long and mainly horizontally aligned launch track for spacelaunch, targeted upwards at the end.

It would use a linear motor to accelerate payloads up to high speeds. All existing and contemplated mass drivers use coils of wire energized by electricity to make electromagnets. Sequential firing of a row of electromagnets accelerates the payload along a path. After leaving the path, the payload continues to move due to inertia.

[edit] Ram Accelerator

A ram accelerator has the same function as a gun; i.e., it is a device for accelerating projectiles; however, it is entirely different in that jet-engine-like propulsion cycles utilizing ramjet and/or scramjet combustion processes are used to accelerate a projectile to extremely high speeds.

[edit] Slingatron

In a slingatron, projectiles are accelerated along a rigid tube or track that typically has circular or spiral turns, or combinations of these geometries in two or three dimensions. A projectile is accelerated in the curved tube by propelling the entire tube in a small-amplitude circular motion of constant frequency without changing the orientation of the tube, i.e., the entire tube gyrates but does not spin.

This gyration continually displaces the tube with a component along the direction of the centripetal force acting on the projectile, so that work is continually done on the projectile as it advances through the machine. The centripetal force experienced by the projectile is the accelerating force, and is proportional to the projectile mass.

[edit] Space gun

Main article: Space gun

A space gun is a method of launching an object into outer space using a large gun, or cannon.

However, even with a "gun barrel" through both the Earth's crust and troposphere, the g-forces required to generate escape velocity would still be more than what a human tolerates. Therefore, the space gun is restricted to freight and ruggedized satellites.

[edit] Spaceplanes

Main article: Spaceplane

A spaceplane is an aircraft designed to pass the edge of space. It combines some of the features of an aircraft and some of a spacecraft. Typically, it takes the form of a spacecraft equipped with wings and one or more rocket engines and sometimes additional propulsion as well.

However, they cannot yet reach further out in outer space without rockets, since all their other current propulsion mechanisms are dependent on the atmosphere. Therefore, so far, they have only been helpful with assisting proper rocket-driven vehicles through the first distance towards outer space, such as Scaled Composites White Knight.

However, some jet-engine based designs such as scramjets could potentially achieve orbit, and reusable designs like Skylon which uses precooled jet engines up to Mach 5.5 before employing rockets to enter orbit appears to have a mass budget that closes with a larger payload than pure rockets.

[edit] References

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