Ennetech by Erasmus and Kinkajou Authors

 

 

 

Erasmus and Kinkajou share their vision of technologies that will help us on our way.

 

Skyhooks, Rockets & Gravity

 

 

 

 

The physical parameters required for a space elevator are impossible for planet earth.

But what about a "virtual" elevator with a virtual structure in part > force linkages rather than physical matter linkages.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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EMF for Orbital Engine Boosting:
Magnetic vs Light Photons

KinkajouKinkajou : How about a Quick word on any thoughts about transferring power to any spacecraft seeking to escape to GEO?

ErasmusErasmus :   The quantum particle which carries magnetism is the electromagnetic photon. Photons of one specific energy level generate magnetic energy. Other photons such as Light photons carry a lot more energy, are more directional (less wavelike) but are less able to be used directly than are for example magnetic photons.

Magnetic energy is unfortunately more wavelike rather than particle like due to the large wavelength of the photon. Light particles are much more amenable to being focused by concave type mirrors that even with current technology can be easily constructed.

However, higher frequency electromagnetic photons carry more energy, can be beamed more tightly, and can be used to transmit energy by radiation. A laser can transmit energy in light frequencies to a tight specific point up to hundreds of thousands of kilometres away.

Light energy is more particle like and tends to disperse less than longer wavelength electromagnetic photons. However, longer wavelength photons (cf light photons), are still capable of being transmitted in a tight beam format.

This means energy can be delivered to a point in time and space. If this energy can be delivered fast enough and harvested fast enough it can be used to perform mechanical work at that point in time and space.

The obvious suggestion would be that the energy can be used to heat propulsive gases and to provide thrust through electromagnetic induction to propulsive gases. This would reduce the amount of chemical energy (mass) required to be carried by spaceship.

While the spaceship would need to carry molecules to provide mass in/ mass out propulsive force, they would not need to carry molecules to provide chemical energy to drive these reactions.

ErasmusErasmus : This proposal separates propulsion into two aspects. Firstly you need to provide fuel mass. Secondly you need to provide energy for the fuel mass.

ErasmusErasmus : By using transmission of energy from ground-based stations, you lose the necessity to ship mass simply for the purpose of generating energy. This means that a rocket engine can generate more propulsion (momentum thrust) by reducing mass and increasing the velocity of exhaust gases.

I.e. 50% less mass would require double the velocity to generate the same momentum. This would result in substantial decreases in chemical energy required to be carried. Also by carrying less mass, you need to generate less propulsion (momentum thrust).

 

Skyhook to Orbit Skyhook to Orbit

 

 

 


Gravity In Orbital Engines

KinkajouKinkajou : Any other ideas?

ErasmusErasmus : (Considering his next words carefully): Well I had the idea that if humans could generate gravity, this itself could be used to provide thrust to launch spacecraft. Gravity is an ideal propulsive force for a spacecraft.

It is massless, so we don’t have to worry about carrying fuel or reaction mass for our engines. Much of the weight of our current rockets is expended in carrying their own oxygen and fuel to allow continued combustion in the cold relatively airless environment of the upper mesosphere and onward.

Gravity drive could get us off the ground. Gravity drive could pull us into space. Gravity drive could propel us in space. Gravity drive could get us out of space and then could probably do it all again. Currently we could go up and back, land and then do it all again without the need for refuelling. Gravity could protect us from radiated high velocity particles from the sun.

Every flying machine that humans have built essentially needs to be refuelled after a good long trip, but gravity drive could well last long enough to essentially create a drive that does not need to be refuelled.(not immediately anyway).

The only problem is that we don’t really know much about generating gravity and we don’t probably understand the theory well enough to work with the fields or dimensions of matter to allow us to generate gravity. (Current theories such as string theory hold that space is made up of 11 dimensions, not the four that we are currently used to.

Humanity's need to leave our planet is becoming acute. Sadly.
Humanity's need to leave our planet is becoming acute. Sadly.

 

KinkajouKinkajou : Wow! That's incredible.

 

KinkajouKinkajou : How about we finish off by discussing what other suggestions people have had to reach GEO: geostationary earth orbit and escape velocity?

 

Proposals to get to earth orbit geostationary height have included over the last 100 years:

KinkajouKinkajou : How about building a tower to geostationary orbit?

ErasmusErasmus :  The world's tallest structure is the 830m tall Burj Khalifa in Dubai, United Arab Emirates.

Since the distance to geostationary orbit is 35 000 km, (i.e. 35000000m), humanity would have to build a structure 43000 times taller than the largest ever built. Said structure (scaled up from the building size) is also three times the diameter of the planet. There is no known building material that could withstand the compressive force generated simply by the weight of the building material.

KinkajouKinkajou : Ah well seemed like a good idea at the time.

 

 

 

Orbital Access via Cable/Ladder/Skyhook/Space Elevators

KinkajouKinkajou : How about using a rope lowered down to the earth from a space station in orbit?


Space Elevator

ErasmusErasmus :  The theory was refined to use thicker material towards the middle of the rope and thinner material at the edges: reducing the mass of the rope required. I had a look on Wikipedia about this one. (I just like to remind you to help support our Internet institutions, please donate!) .

Again there is no material in existence that could generate the tensile strength required to make a rope, cable or tether of sufficient strength. Typical breaking lengths for modern structures are:

Metals like titanium, steel or aluminium alloys have breaking lengths of 20-30 km. Kevlar, fibreglass and carbon/graphite fibre have breaking lengths of 100–400 km.

Nano-engineered materials such as carbon nanotubes and, more recently discovered, graphene ribbons (perfect two-dimensional sheets of carbon) are expected to have breaking lengths of 5000–6000 km at sea level, and also are able to conduct electrical power.

 

 

KinkajouKinkajou : shaking his head :  They all still come up short. We need a length of at least 35000 km to reach a geostationary point above the earth, probably a lot more depending on the design of the sky bridge and any counterweight system. The breaking tensions are not enough to withstand the strain.

Also many of these breaking lengths(lengths at which the tensile strength of the material equals the tension strain placed on the material) are based on laboratory projections drawn from perfect flawless structures.

Everyone knows that it’s the imperfections in a material that lose much of the strength and these imperfections become a lot more common when materials are scaled up from laboratory assessments to functioning in the real world.

KinkajouKinkajou : However, that still means the suggestion could well be valid, if not just on the earth. Some people feel that Technology as of 1978 could produce elevators for locations in the solar system with weaker gravitational, such as the Moon or Mars or some of the smaller orbiting bodies in the solar system.

KinkajouKinkajou : So our goal in all this is to achieve escape velocity to a geostationary orbital height of 35000 km requires a final velocity of 4386 m/s =15790 km/h.

Space Gun to Orbit Space Gun to Orbit

ErasmusErasmus : I have looked this up

Escape velocity varies according to height above the surface of the earth. On the surface of the Earth, the escape velocity is about 11100 metres per second.

This is approximately 34 times the speed of sound (Mach 34) and  Several times the muzzle velocity of a rifle bullet (up to 1.7 km/s).

Because we have selected geostationary orbital height, there is essentially one solution for what is the escape velocity at this height. I.e. 15790 km/h requires a final velocity of 4386 m/s

The escape velocity relative to the surface of a rotating body depends on direction in which the escaping body travels. For example, as the Earth's rotational velocity is 465 m/s at the equator,

A rocket launched tangentially from the Earth's equator to the east requires an initial velocity of about minus 465m/s  I.e. a total of 10.735 km/s relative to Earth to escape

Whereas a rocket launched tangentially from the Earth's equator to the west requires an initial velocity of about Plus 465 m/s i.e. a total of 11.665 km/s relative to Earth. 

A geostationary orbit is one in which an object in space appears to stay above one point on the Earth at all times through the day. This means that it has a “period” of almost a day. It takes a day to rotate around the earth.

An earth makes one complete rotation in actually about 23 hrs and 56 minutes. {We usually define a rotation as being from maximum sun height noon to maximum sun height: noon the next day.}

The reason noon tomorrow is not 23 hours and 56 min. after noon today is that the Earth has moved a little bit in its orbit around the Sun during this time. Because of this, the Sun is now in a slightly different direction from the centre of the Earth, and the Earth has to turn slightly more than one rotation to bring the Sun to due south again. (This, of course, takes 4 minutes longer, making the familiar 24 hour day.)

Now back to the actual orbit of a satellite around the Earth: Since geostationary satellites remain over the same point on the Earth, their orbits must have a period equal to the Earth's rotation on its axis = 23h56m. They also must go around the equator (or else they would appear to move North and South throughout the day), and go in a circular orbit (or else they would appear to move East and West throughout the day).

 

Karmen Line In Orbital Karmen Line In Orbital

 

Now from these constraints, we can calculate the one specific height above the Earth where a geostationary satellite has to go. If we put it too high, the satellite would move too slowly. If we put it too low, it moves too fast.

If you subtract the radius of the Earth from this answer, you get the height above the Earth for a geostationary satellite: We calculate 35,000 km (there are formulas available which can calculate this).

If you are setting up an orbital elevator, it becomes obvious that it needs to be set up connecting to a point in geostationary orbit around the Earth

KinkajouKinkajou : Tell us about the Space Elevator proposal !

ErasmusErasmus : A space elevator for the planet earth consists of a high tensile strength cable designed to be thickest around its middle where it needs to support the most weight and thinnest at ground level where there is no weight to support, and thinnest in space where there is no weight.

NASA researchers noted that "maximum stress [on a space elevator cable] is at geosynchronous altitude so the cable must be thickest there and taper exponentially as it approaches Earth.

Newer designs include a counterweight to anchor the rope into space and allow the payloads to be pulled up the cable, past geostationary orbit and into free orbit.

Counterweights would have to be positioned a substantial distance away from the earth, close to the moon. If a really big asteroid was used and orbital positioning control of the rock was lost, the rock that knocked off the dinosaurs would end up being a fine memory. (Compared to what we just brought upon ourselves).

ErasmusErasmus : Space elevators have been also named as referred to as 

Orbital elevators
space bridges
space ladders
space lifts
skyhooks or
orbital towers.

Simple Skyhook Simple Skyhook

 

ErasmusErasmus : There are some not so obvious problems associated with travelling up a space ladder. The ladder is a minimum of 35000 km long to GEO. It would take a substantial amount of time to travel this distance.

The payload on the space elevator would travel through the Van Allen radiation belts around the earth. Biologicals would need shielding to survive.

The environment of space is vacuum, so the payload needs to be protected from vacuum, which required a significant level of pressure engineering. Incidents in space are remote from earth, and help at any time is very unlikely, especially of the space elevator is not functioning.

The slightest hit or injury to the cable would reduce the tensile strength substantially. A bird shitting on the cable would probably destroy it as may a micrometeorite in space.

Erasmus: A number of scientists have proposed building Earth space elevators. Their calculations call for a fibre composed of epoxy-bonded carbon nanotubes with a minimal tensile strength of 130 GPa (19 million psi) (including a safety factor of 2).

However, tests in 2000 of individual single-walled carbon nanotubes (SWCNTs), which should be notably stronger than an epoxy-bonded rope, indicated the strongest measured as 52 GPa (7.5 million psi).[15] Multi-walled carbon nanotubes have been measured with tensile strengths up to 63 GPa (9 million psi).

Carbon nanotubes are one of the candidates for a cable material. They are also are able to conduct electrical power.

The challenge now remains to extend to macroscopic sizes the production of such material that is still perfect on the microscopic scale (as microscopic defects are most responsible for material weakness). The current (2009) carbon nanotube technology allows growing tubes up to a few tens of centimetres only.

Real Space Station Real Space Station

ErasmusErasmus : As the car climbs, the elevator takes on a 1 degree lean, due to the top of the elevator traveling faster than the bottom around the Earth (Coriolis force).

The horizontal speed of each part of the cable increases with altitude, proportional to distance from the centre of the Earth, reaching orbital velocity at geostationary orbit. Therefore as a payload is lifted up a space elevator, it needs to gain not only altitude but angular momentum (horizontal speed) as well.

This angular momentum is taken from the Earth's own rotation. As the climber ascends it is initially moving slightly more slowly than the cable that it moves onto (Coriolis force) and thus the climber "drags" on the cable.

The overall effect of the centrifugal force acting on the cable causes it to constantly try to return to the energetically favourable vertical orientation, so after an object has been lifted on the cable the counterweight will swing back towards the vertical like an inverted pendulum.

Space elevators and their loads will be designed so that the centre of mass is always high-enough above the level of geostationary orbit  to hold up the whole system. Lift and descent operations must be carefully planned so as to keep the pendulum-like motion of the counterweight around the tether point under control.

When the payload has reached a level greater than 66% of the distance from the surface to GEO, the horizontal speed is enough that the payload would enter an orbit if released from the cable.

The opposite process would occur for payloads descending the elevator, tilting the cable eastwards and insignificantly increasing Earth's rotation speed.

Future Space Station
Future Space Station

 

ErasmusErasmus : Yoshio Aoki, a professor of precision machinery engineering at Nihon University and director of the Japan Space Elevator Association, suggested including a second cable and using the conductivity of carbon nanotubes to provide power.

Various mechanical means of applying power have also been proposed; such as moving, looped or vibrating cables.

Various methods have been proposed to get that energy to the climbing spacecraft. One possibility is that of using wireless energy transfer.

Wireless energy transfer such as laser power beaming is currently considered the most likely method. Suggestions have covered using megawatt powered free electron or solid state lasers in combination with a specifically sensitized photovoltaic array on the climber designs powered by power beaming.

This efficiency is an important design goal. Unused energy must be re-radiated away with heat-dissipation systems, which add to weight and complexity

KinkajouKinkajou : What about Launching into deep space ?

ErasmusErasmus : An object attached to a space elevator at a radius of approximately 53,100 km will be at escape velocity when released. Transfer orbits to the L1 and L2 Lagrangian points can be attained by release at 50,630 and 51,240 km, respectively, and transfer to lunar orbit from 50,960 km.

The velocities that might be attained at the end of Pearson's 144,000 km (89,000 mi) cable can be determined. The tangential velocity is 10.93 kilometres per second (6.79 mi/s), which is more than enough to escape Earth's gravitational field and send probes at least as far out as Jupiter. Once at Jupiter, a gravitational manoeuvre permits solar escape velocity to be reached.

Impacts by space objects such as meteoroids, micrometeorites and orbiting man-made debris, pose another design constraint on the cable. A cable would need to be designed to manoeuvre out of the way of debris, or absorb impacts of small debris without breaking.

Virgin Space Ship Virgin Space Ship

 

KinkajouKinkajou : How can a cable under strain manoeuvre away from impacting debris or micrometeorites? It is sounding like we have a long long way to go before we will be building space elevators on earth. However, the numbers could indeed add up for smaller planetary or moon bodies within our solar system. Mining operations on moons could be made viable with the use of this incredible technology.

 

 

 

Economics

KinkajouKinkajou : What about the economics of building and maintaining space elevators?

ErasmusErasmus : With a space elevator, materials might be sent into orbit at a fraction of the current cost. As of 2000, conventional rocket designs cost about (US$25,000 per kilogram) for transfer to geostationary orbit.

 Current proposals envision payload prices starting as low as $100 per pound ($220 per kilogram), similar to the $5–$300/kg estimates of the Launch loop, but higher than the $310/ton to 500 km orbit Quoted to Dr. Jerry Pournelle for an orbital airship system.

It becomes obvious that the first country to build and operate a system such as a space elevator  would enjoy substantial cost advantages to accessing economic activities within our solar system and within space.

KinkajouKinkajou :  Explain how you think orbiting vehicles travel through space?

If an object attains escape velocity, but is not directed straight away from the planet, then it will follow a curved path. Although this path does not form a closed shape, it is still considered an orbit.

The shape of the orbit will be a parabola whose focus is located at the centre of mass of the planet. An actual escape requires of course that the orbit not intersect the planet nor its atmosphere, since this would cause the object to crash. When moving away from the source, this path is called an escape orbit.

In reality there are many gravitating bodies in space, so that, for instance, a rocket that travels at escape velocity from Earth will not escape to an infinite distance away because it needs an even higher speed to escape the Sun's gravity.

In other words, near the Earth, the rocket's orbit will appear parabolic, but eventually its orbit will become an ellipse around the Sun, except when it is perturbed by the Earth whose orbit it must still intersect.

Earth Magnetic Fields Earth Magnetic Fields

 

 

Orbital Access via Rockets

KinkajouKinkajou : So explain to us about Rocket engine propulsion.

ErasmusErasmus : The rocket engine uses the same basic physical principles as the jet engine for propulsion. That is it generates thrust from exhaust gases. It is distinct in that it does not require atmospheric air to provide oxygen; the rocket carries all components of the reaction mass.

Rocket engines are used for launching satellites, travelling in space and in our landings on the Moon and Mars. Rocket engines are used for high altitude flights as they have a lack of reliance on atmospheric oxygen and this allows them to operate at any altitude.

They can also operate anywhere where very high accelerations are needed since rocket engines themselves have a very high thrust-to-weight ratio.

However, the high exhaust speed and the heavier, oxidizer-rich propellant results in far more propellant use than turbofans although, even so, at extremely high speeds they become energy-efficient. A rocket needs to be much bigger than an air breathing plane or jet because it needs to carry not only its fuel but also all its own oxygen.

Rockets typically have few moving engine parts, can travel efficiently between Mach 9 and Mach 30+, have no complex air inlet fans or compressors, have high speed or supersonic exhaust and have very high temperature combustion and high expansion ratio nozzle gives very high efficiency- at very high speeds.

On the down side they Need lots of propellant and the Extreme thermal stresses of combustion chamber can make reuse harder. Typically rockets require carrying oxidizer on-board which increases risks. They are extraordinarily noisy .

KinkajouKinkajou : So let’s revisit your proposals for achieving orbit. As I remember you said that there are three realistic separate options for achieving GEO: geosynchronous earth orbit.

  • 1. Rocket propulsion:.
  • 2 Magnetic propulsion or transmitted electromagnetic energy mediated propulsion e.g. radiofrequency type outputs. Magnetic energy pushes, while EMF energy will provide heat for propulsion.
  • 3. Gravity generation

 

You also said that additional systems may be used to add thrust:

  • Scram Jets / Ramjets.
  • Using a plane or rail gun type structures to create a portion of the initial speed
  • Using magnetic pull from a structure located off the earth
  • Transmitting EMF or RF energy to the space vehicle to increase the temperature of the engine substrate, thereby generating more propulsive force.

 

KinkajouKinkajou : We have talked about rocket propulsion, transmitting energy, and gravity drives. We have also talked about scramjets.

 

 

Orbital Access: Combining Launch Technologies

ErasmusErasmus : I think the final discussion point should focus on methods of adding launch velocity. There has been substantial amounts of work done in launching space vehicles from planes. This achieves part of the orbital velocity required to escape the Earth’s gravity well.

It substantially reduces the weight of the space vehicle. This is because the bulk of the carried chemical fuel is required to create the thrust for the mass of the vehicle at the lowest speeds.

However, I naturally shy away from the complexity inherent in combination launch systems to help to achieve orbital escape velocity. The problem with  complex systems occurs when one subcomponent of the system fails.

Then the space vehicle is unable to attain escape velocity orbit. Achieving orbital velocity is dangerous enough, even using relatively simple systems such as rocket propulsion without adding layers of complexity and multiple other points of failure.

Still it does reduce the size of the launch vehicle and so perhaps cost if the combined systems can be optimized.

KinkajouKinkajou : So what have you learned, Goo?

Our Little Numbat FriendGoo : I think there are a number of niches for which existing technologies provide adequate solutions. Commercial realities i.e. costs, become very important in large or complex systems. There is a need to develop simple systems which can provide the lift or propulsion to enable the achievement of orbit. Currently the proposals that I think are most exciting involve transmitting EMF energy or possibly generating gravity.






EMP weapons : EMP propulsion
EMP weapons : EMP propulsion