Erasmus : If the Human Race ever hopes to escape the bounds of planet earth, it will need some sort of technological solution to the problem of lifting payloads (be they people, animals or cargo) into orbit, out of the earth’s gravity well.
The first step to exploring the solar system and exploring space is to get into orbit above the planet earth.
The next step to exploring space, is to escape the sun's gravitational well.
It is even harder to escape the sun’s gravitational field than it is to escape the earth’s gravitational field. The energy required to escape from the sun’s gravitational field (starting from earth orbit) is about four times as great as that required to escape into earth orbit from the earth’s surface.
So if we can’t escape from earth’s gravity, escaping from the sun’s gravity would indeed be an impossible task.
The main difference with the sun's gravity field (to that of the Earth itself), is that it is very spread out ,where we are orbiting at 93 million miles (149 million km) out. Consequently we are able to take a lot more time to generate the lift or speed to reach solar escape velocity.
The earth’s gravity field at ground zero, right on the surface of the planet is much more intense. So we need to generate a lot more lift force in a lot less time to escape earth’s gravity well. This creates problems because we need rapid force production and rapid speed attainment to escape from the earth's gravity well.
These time factors are less important when trying to escape from the sun's gravity well. The earth's gravity well could therefore be described as "steeper" than that of the sun: a shape or distinction that has consequences.
Earth Within Gravity Well
Kinkajou : Sounds like we are never going to leave. We have to escape from two gravity wells, getting successively larger to get into space. How do people work all this stuff out?
Erasmus : Let’s choose a geostationary earth orbit as a reference point for discussion. A geostationary orbit is where an object stays in exactly the same position in the sky above you throughout the day.
( Using this simple fact as a start point, you can actually have a crack at calculating escape velocity yourself. The earth rotates in 24 hours, and has a diameter of about 10.000km, the extra bit of diameter to get into orbit being an addition to this, depending of course on the height at which you intend to orbit. Using this you can work out a "rough" speed in orbit).
Due to the effect of gravity, it is extremely difficult to get into orbit. In effect, to get into orbit requires the use of force to lift things about 35000 km (geostationary orbital height) against the constant force of gravity and requires the acquisition of a speed (escape velocity) at this height (35000 km) of about 15790 km/h (4387m/s).
This statement is true however only for ballistic trajectories: such a bullet fired from a gun. From ground level, a bullet fired from a gun, needs a ballistic escape velocity of 40320 km/h). The maximum sped required to be attained by a powered projectile such as a rocket is less than that required to be attained by a ballistic projectile such as a bullet.
The difference is quite substantial in terms of the energy required to be expended to escape from the earth. It therefore is easier for a powered object such as a rocket to escape from the earth than it is for a bullet to escape from the earth. (The maximum velocity needed to be achieved to get to orbit being much smaller for the rocket).
Escape Velocity From Earth
Kinkajou : (looking puzzled): Shouldn’t the final speed be the same?
Erasmus :“Well apparently not “. The answer lies in the differences between a rocket and a ballistic projectile.
A rocket, for example, generating a propulsive force will continue to gain kinetic energy and travel away from the planet, in any direction, at a speed lower than escape velocity so long as it continues to generate its propulsive force. If the rocket’s speed is below its current escape velocity and the propulsive force is removed, the rocket will fall back to the surface.
If its' speed is at or above the escape velocity and the propulsive force is removed, it has enough kinetic energy to "escape" and will not fall back to the surface. So long as the rocket continues to generate its propulsive force, its speed will be unimportant. The lower the speed of course the longer it will take to reach geostationary orbit and the more fuel will need to be expended to get there.
So, due to fuel constraints, the rocket needs to travel quickly to orbit rather than take days to reach a final height of 35000 km.
Kinkajou : But surely, using less energy in attaining higher speeds is counterbalanced by the need to provide propulsive force against gravity for longer.
Erasmus : Well, Yes there is that.
Kinkajou : Heh ! “I know a few ways to get into orbit.”
Erasmus : grimacing:” Enough of that”. Any idiot can get high. Let’s stay serious, so we can achieve something. Let’s talk about what the answer may be, and then have a discussion about what the answer is not.
Humanity's need to leave our planet is becoming acute. Sadly.
Options To Achieve Orbit
Erasmus : I think that there are three realistic separate options (and one weird option) for achieving GEO: geosynchronous earth orbit, in future tech.
- 1. Rocket propulsion: We got it and we are using it but damn, it is expensive. A number of different new technologies can be applied to this traditional solution to extend its "use by" date.
- 2. Magnetic propulsion or transmitted electromagnetic energy mediated propulsion. Magnetic energy pushes, while EMF radio frequency photons transmit energy to provide heat for propulsion.
- 3. Gravity generation
- 4. An outlying tech is the ability to deliver push to electrons vis electromagnetic photons, mimicking a form of propulsion. This is the reputed technology of the "Greys". Electrons absorb photon energy and are pushed as a result, supposedly resulting in a high G propulsion with very even distribution of force, reducing inertia issues for large bodies, by transmitting inertia directly to its component small structures: namely the electrons.
Kinkajou : I have heard of some other technologies to provide thrust to get us into orbit?
Erasmus : Additional systems may be used to add thrust to rockets:
- 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.
- Skyhooks or orbital elevators are probably not a realistic option on a planet with a gravity well the size of the earth. This is because the tensile strength of the materials that can be used in the structure of the orbital elevator cables, is not sufficient to cope with gravity and its own weight.
It may be possible to bypass some of these restraints by the combined use of short lengths of magnetically coupled cables, but this is not an option which has been seriously explored at this point in time.
These systems are not necessarily exclusive solutions to the problem of achieving geostationary orbit. Some of the applications overlap and the final solution could well use all these solutions. Unfortunately, the more elements in a solution the more complex the final answer and the more things that can go wrong.
Combining many of these options to provide propulsion could indeed reduce the weight of rockets, but at a cost of increasing complexity. With increasing complexity, failure of any subsystem may guarantee a launch failure, when theory meets reality as we race into space.
The biggest problem with rockets is the need to carry your own fuel especially oxygen into the upper atmosphere. Scram jets or ramjets bypass this problem at least in the lower atmosphere by scooping up environmental oxygen and perhaps nitrogen to burn within the jet engine.
However, however once you reach a height of about 50 km, the air pressure is only about 1/1000 of an atmospheric pressure, approximately 0 .015 psi. Obtaining enough oxygen for combustion at this height, requires that oxygen be stored and transported within the space vehicle from its launch. This has substantial weight implications.
Erasmus : About the Earth's Atmosphere
In considering the achievement of "orbit" ,consider that the International Space Station orbits between 330 to 410 km above the surface of the earth, within the thermosphere of the earth.
From highest to lowest, the five main layers are:
- Exosphere: 700 to 10,000 km (440 to 6,200 miles)
- Thermosphere: 80 to 700 km (50 to 440 miles)
- Mesosphere: 50 to 80 km (31 to 50 miles)
- Stratosphere: 12 to 50 km (7 to 31 miles)
- Troposphere: 0 to 12 km (0 to 7 miles
Kinkajou : It's obvious that you need a rocket to escape the earth as there must be a point at which the atmosphere"runs" out of air and planes can no longer fly. So what is the point above which an aircraft can no longer fly?
Erasmus : The Karmen line represents the official boundary between the Earth’s atmosphere and space. Karmen was the 1st to calculate that at this altitude the Earth’s atmosphere is too vacuous to support aeronautical flight.
A space vehicle at this altitude would have to travel faster than orbital velocity to achieve sufficient aerodynamic lift to support itself. The atmosphere actually does not end abruptly at any given height but becomes progressively more sparse with increasing altitude.
At the Karmen line which is above the mesosphere, molecules of gas making up the atmosphere are sufficiently spaced that they rarely interact with each other. For example one oxygen (O2) molecule travels an average of 1000 m between collisions with other molecules.
Erasmus : What most of us would regard as the top of the atmosphere, is known as the stratosphere. The “stratosphere” starts at an altitude of 50 km (30 miles).
This is a dynamically stable layer without convection or regular turbulence, a temperature at the top of around -3 ° C (27°F), predominantly composed of nitrogen dioxide (NO2) molecules and carbon monoxide (CO) forming stable layers.
What I find unusual is that the air temperature actually rises as you go into the higher levels of the stratosphere.
Kinkajou : How Bizarre!
Earth Atmosphere to Orbit
Kinkajou : I suddenly realised that a plane in the upper atmosphere is actually in a really really cold place. I can see that a plane burning fuel for propulsion , would lose a lot of its energy just heating up the intake gas just to room temperature: a basic starting point for most of us when contemplating the operation of combustion engines on the surface of the planet.
Erasmus : Yes indeed. The very low temperatures as we ascend in height means that substantial quantities of the heat generated by chemical reactions intended for propulsion via rockets, may need to be used to heat the chemical fuels(e.g. oxygen/nitrogen and propellants) to standard temperature and pressure. (25degrees C and one atmosphere pressure).
(Depends of course on whether you scoop up ambient oxygen or discharged cool liquid oxygen from a storage tank ).
Storing cold compressed oxygen and fuel also causes efficiency losses. Many rockets carry their oxygen with them compressed into tanks. But when this gas is expanded as it is fed into the engine, it of course becomes very very cold. in effect stored oxygen is liquid oxygen as it is released out of its storage tank.
This liquid oxygen is then cooled further as it needs to be expanded before being fed into the engine. This expansion creates further cooling in much the same way that an air conditioner achieves its cooling effects.
Nuclear Power for Orbital Engines
Kinkajou : How about nukes?
Erasmus : Nuclear fission reactors are capable of generating enough energy fast enough to be useful, in powering rockets.
However, they would be operating in their exponential heat and energy production range. There is very little leeway between the rocket engine delivering push and the rocket engine delivering a bang. This means that practically fission reactors cannot be used to provide propulsive energy, (too unstable and dangerous). We prefer to use chemical fuels as they are so much more controllable.
Gravity for Orbital Engines
Kinkajou : So what's so sexy about the competitors to the rocket , such as the "gravity drive"?
Erasmus : Generating gravity is the only option which does not mandate the ejection of fuel , such as in a rocket engine.
Gravity can be used to provide lift.
Gravity can also be used to provide extra propulsive force for the fuel.
All our other propulsion generating systems are based on mass in / mass out technology. This requires fuel (mass) and energy. Gravity is a propulsive system which can operate without ejecting fuel (mass). (Perhaps the electron drive of the "Greys" may be another example, if it exists.)
Ramjets and Scramjets for Orbital Engines
Kinkajou : : (Asking for some more details): Firstly, tell me about ramjets and scramjets.
Erasmus : Ramjets require air to enter the engine at high speed. They do not operate from a stationary start as there is no airflow into the engine. To start a ramjet needs airflow generally somewhere over 400 kph. This means that at first another engine must accelerate the craft to this speed. Only then can the ramjet be started. Air is compressed into the engine at the air intake.
Due to the formation of shock waves at the air intakes, ramjets cannot feed air into the engine at speeds above about mach1.2. This effectively limits the top speed that this type of engine can produce.
As the air enters the engine, the shape of the front air intakes compresses the air into the front of the ramjet. Fuel is added at the mid part of the engine and then ignited at the rear of the engine, creating high pressure. This mixture of hot exhaust gases is ejected out of the rear of the engine.
Kinkajou : looking puzzled: The engine has an opening at both ends. The design is effectively an open tube. Why should any thrust be generated? The air would try to go back and forward at the same time, so no thrust could be generated?
Erasmus :“Good thought, Kinkajou”.
Erasmus : Most jet engines use air compressed by turbines into a reaction chamber, where fuel is then added, input vents closed and hot exhaust gases are discharged out the rear end, creating thrust.
The ramjet design is effectively an open tube but with smaller holes to the front. The combination of these smaller holes to the front and air pushing in from the front creates pressure which effectively seals the front of the engine and forces exhaust out of the rear of the engine generating thrust.
Erasmus : Still at the end of the day, a ramjet is not suitable for launching a spaceship because the finally attained speed is not great enough. (I.e. a max theoretical speed of Mach 1.2) It does have some advantages over normal jet or turbojet engine design though.
A typical turbojet engine requires inlet fans, multiple stages of rotating compressor fans, and multiple rotating turbine stages, all of which add weight, complexity, and a greater number of failure points to the engine design
Kinkajou : What about pulse jets? Are they any different?
Erasmus : A pulsejet is a type of intermittently operating ramjet. They are unfortunately incredibly noisy, are inefficient (they have a low compression ratio), and work poorly on a large scale when experiments have been conducted.
So the next solution is the scramjet. The name "scramjet" comes from the title "supersonic combusting ramjet. These function with air intakes working at hypersonic velocities throughout the entire engine. A scramjet effectively has no moving parts as the movement of the aircraft through the air provides the compression for needed for the intake air.
Theoretical projections place the top speed of a scramjet between Mach 12 and Mach 24. The fastest air-breathing aircraft currently is a SCRAM jet based design, the NASA X-43A which reached Mach 9.8 in trials.
For comparison, the second fastest air-breathing aircraft, the manned SR-71 Blackbird, has a cruising speed of Mach 3.2. Very few scramjet engines have ever been built and flown. In May 2010 the Boeing X-51 set the endurance record for the longest scramjet burn at over 200 seconds.
Kinkajou : Scramjets are obviously not a very mature technology.
Erasmus : riposting:
Well, we are supposed to be looking for new tech and new answers.
Since scramjets use supersonic combustion they can operate at speeds above Mach 6 where traditional ramjets cannot. Another difference between ramjets and scramjets comes from how each type of engine compresses the oncoming air flow.
While the inlet provides most of the compression for ramjets, the high speeds at which scramjets operate allow them to take advantage of the compression generated by shock waves. Shock waves, especially oblique shock waves , form at specific sites within the engine and combustion can be planned around these "functional "structures.
Erasmus : At hypersonic velocities, while the apparent design of the scramjet is simple, a number of factors begin to create technical problems. The chamber materials fail to withstand the working conditions in terms of temperature or pressure. In short, the chamber materials fail.
Maintaining combustion in the supersonic flow environment of the interior of the scramjet also presents additional challenges, as the fuel must be injected, mixed, ignited, and burned within milliseconds.
The high temperatures and pressures generated within an operating engine in high speed flight tend to melt exhaust nozzles. Also, the metal of the engine may be both melted and ignited in combination with very high temperature air.
Functional difficulties arise from funneling shock waves through the engine, posing severe design constraints. Once a shock wave forms in the engine, airflow may be severely curtailed. At high atmospheric elevations, the air is very cold and of low pressure. The cold and very low pressure intake air robs thrust and combustion from the engine, effectively extinguishing it.
Kinkajou : In terms of getting to orbit, how are scramjets going to get us to where we need to be.
Erasmus : In dry air at 20 °C (68 °F), the speed of sound is 343 metres per second. So a scramjet achieving Mach 12-24 gives us a theoretical maximum final launch speed of 4118 m/s to 8237 m/s. (12-24*343).
We need about 4386 m/s at 35000 km height to achieve orbital velocity at this height.
However, the air for a scramjet runs out long before this height, so our scramjet falls short of being able to achieve orbit, through simple lack of oxygen or nitrogen to support combustion. At lower heights above the earth's surface, escape velocity is higher, so the more relevant speed we need to achieve to "escape" the earth's gravity well is 11200 m/s.
Again,the scramjet falls short of achieving orbit because of inadequate speed attainable. Its operation is limited to the atmosphere, which effectively ends at the Karmen line at 100 km height (just above the mesosphere at 85KM height) above sea level.
Air pressure at this level is 1/1000 of an atmosphere at the bottom of the mesosphere and is typically at temperatures of -100 deg C. Both factors (low pressure and low temperature) cause logistic difficulties for a combustion engine that needs to heat its exhaust gases to create thrust.
Still, this technology could get us from jet engine launch speed to a speed that could keep us in orbit if only the launch vehicle had attained enough height.
EMF for Orbital Engine Boosting: EMF flux within Engines
Kinkajou : challenging: Any ideas how to get a bit extra out of this engine?
Erasmus : Well Maybe.
Erasmus :An engine at this speed does not really deal with air as we now it. The high pressures and temperatures within the engine create a quite difficult animal: let’s call it flux or plasma. This opens the door to alternate methods of manipulating the flow.
Possible design improvements include options such as using magnetic flux or electrical flux (perhaps even gravity flux one day),to channel air plasma through the engine, and to reduce wear on components. There may be a way to convert our shielding flux energies into extra thrust.
Such a design would also allow carried fuel and oxygen to be fed into the scramjet engine after the mesosphere is exited after launch to allow continued combustion and continue generation of thrust by the engine. This would reduce the required orbital speed to achieve escape velocity by allowing the launched vehicle to continue on a rocket trajectory as opposed to a ballistic trajectory as we discussed before. This literally halves the required escape velocity for our vehicle.
(ie If we double the velocity of the launch "exhaust gas" , we halve the mass required to be used to provide the thrust).
Kinkajou : contemplating: I don’t think human technical excellence at this time really has much experience with creating and maintain plasma containment or plasma flux fields.
The recent innovations in MRI manufacture mean that we can generate 1.5 tesla magnetic fields (typical for a high grade MRI imaging machine), but I don’t think we’ve really thought about this sort of technology much in terms of rocket propulsion.
The reality is that simple rockets are just relatively easier in terms of where we are technologically at this time, though I’ll really be interested to see where things go.
Plus I think we have not worked out how to get the energy needed to create thrust fast enough , (except from chemical sources) to enable the addition of thrust to the hot exhaust gases.
Maglev to Orbit
EMF for Orbital Engine Boosting: EMF for Energy Transmission
Kinkajou : What next?
Erasmus : I think this flux technology is a bit of a wild card at this time, but it would be interesting to see if it might help us. Some very ancient concepts in electromagnetism may help us with an answer.
Generating magnetic fields is very wasteful of power. In the early days of electricity, Nikola Tesla suggested that we could radiate power away from generators. Edison however won with a much more practically efficient idea.
Transferring electricity along wires achieved greater delivery of the required electricity (power) at a greater distance, in essence more efficiently than just radiating power. However, the key point from Tesla’s concept is that you don’t’ need wire to transit electricity.
So if we could direct a magnetic field (which is made up of low frequency light photons), we could deliver energy at a specific place and time without the need for wiring. If it were possible to create a laser that fired photons with energy levels in the magnetism range (vs. the light frequency range), we could deliver magnetic energy or electromagnetic energy at distance.
Magnetism could be used as a propulsive force with low loss transmission due to the highly directional nature of the laser directed energies. (We will talk about this on the next page).
So we could use ground based magnetic lasers to push a launch vehicle into orbit using low cost ground based electrical sources. We could use ground based magnetic lasers to drive electrical or magnetic machinery aboard our space craft to generate thrust or electricity.
Kinkajou : Sounds sort of interesting, but I think there might be some problems in making magnetic frequency laser photons.
Erasmus : I agree. I can see a few problems as well. But still the possible potential exists. I think you could launch say 20 tons of payload to orbit for the price of 15 minutes electricity from say 100 Megawatts worth of ground based power stations, if you could generate laser magnetic photons. So technically, just in terms of energy, the proposal may be achievable.
But, And there is but:
The First problem that I see is that magnetic level energy photons are by nature more wavelike rather than particle like. Particles can be directed in tight streams, whereas waves tend to spread out and therefore to diffuse the energy. So in practical terms photons with magnetism like energy levels may not “beam “well.
EMP protection form magnetic launch Systems
Erasmus : Secondly, we really don’t have any way to "reflect" or "direct" photons with these energy levels. We tend to use physical mirrors to bounce photons around.
Unfortunately magnetic photons can go through even inches of metal or steel. This means that we may need to use some sort of “field” reflecting mechanism. Most designs that deflect magnetic photons use active magnetic fields to deflect incoming photons. They do not use solid mater to trap or reflect the "magnetic" photons.
Again, as you said before, we really don’t have a lot of experience with use of artificially generated fields to control and reflect deflect photons. I know there are exceptions like the Hadron colliders and cyclotrons, but these are all at a research level not at an industrial or commercial usage level at this stage of our technology.
Erasmus : Thirdly, there will be targeting and dispersion inefficiencies in generating these quantities of magnetic photons, so delivering the energy to where it is needed from where it is made is a skill we will probably need to develop.
On the plus side magnetic photons are probably a lot less susceptible to atmospheric distortion than light photons so maybe targeting would be easier than we think.
Kinkajou : What happens when your neighbouring country, thinks you’ve just launched an EMF weapon at their nearest city? That much magnetism would cause Merry Hell with electrical systems over a wide area.
Erasmus : Yes I can see that. You may have to put your launch facility in the middle of nowhere. Fortunately there are places in the world, e.g. Australia where there is lots of nowhere, “nowhere” near the equator (which is a favourable launch situation), with stable climate and in a stable and commercially responsible working environment with relatively controlled levels of corruption.
EMF for Orbital Engine Boosting: EMF for Orbital Vehicle Boost
Erasmus : There is that added possibility of using magnetism to deliver electrical energy to the launch vehicle, not just to push the launch vehicle.
Also as we gain experience with flux and containment fields which are themselves likely to be magnetic or electrical field based, this technology may spill over into engine design and gain humanity some extra cookie points there.