Mag Beam acceleration to/from lunar surface

Calliban · 2022-01-02 12:34:38

Mag Beam is being discussed as a potential means of accelerating the large ship that is being developed by Robert, with the help of others. It raises an interesting question in my mind. The surface of the moon is hard vacuum, without any atmospheric gas that would otherwise attenuate an ion beam. Additionally, the moon has no magnetic field to divert the course of charged ions, although there are some local magnetic anomalies.

The question: Could a battery of ion guns, located on the moons surface, be used to decelerate objects intended to land on the moon? Could we fit incoming payloads with parachutes made from coiled wire and use stationary ion generators to land objects, with incoming velocity >Ve? If so, this would dramatically reduce the propulsive effort associated with delivering supplies to the moon. Presumably, the opposite could be achieved as well. Payloads of lunar materials could be lifted from the surface and propelled all the way to lagrangian points using tightly focused ion beams.

Presumably, the moon has abundant supplies of Ar-40 trapped beneath its surface, generated by aeons of decay of K-40. This would be an ideal propellant for an ion beam generator.

Concerning the ballistic delivery of materials to planetary surfaces: Ion beam deceleration clearly won't work on Mars. But such units mounted on Phobos, could be used to remove a lot of the kinetic energy that incoming payloads would otherwise have upon entry at the top of the Martian atmosphere. Alternatively, a Mag Beam could be used to decelerate individual projectiles that are targeted at Phobos. The projectiles can then be delivered to Mars surface using a Star Ship in SSTO mode.

Last edited by Calliban (2022-01-02 12:43:27)

SpaceNut · 2022-01-02 12:40:03

The topic sounds promising once we have ships leaving the bounds of LEO and are on the way there. We know that it takes about 3 days to coast there once we escape earths gravity well. So even after we are half way there and focused on the target the energy would slowly break it into orbit or for landing reducing the fuels required to land.

tahanson43206 · 2022-01-02 13:12:43

For Calliban re new topic ...

Best wishes for success with this (to me very promising) new topic!

Hat's off to kbd512 for giving the entire set of ideas a massive boost in his "Practical Large ship" topic.

(th)

SpaceNut · 2022-01-02 17:39:07

condensed post

kbd512 wrote:

Propulsion
The more I look at the MagBeam and M2P2 propulsion concept for the large ship concept, the better it looks. Specific Impulse ranges between 50,000 and 90,000 seconds for M2P2. MagBeam would require 15GW of input power and 350t of propellant, which could be N2 siphoned off from the upper atmosphere. The 15GW for MagBeam would be supplied by a regenerative fuel cell or batteries and solar panel power station in orbit around Earth, and would clear the Van Allen belts in mere hours. The power would be supplied by a 2,500t PEM fuel cell that produces water from LOX/LH2. A 1,000kg spacecraft with a 100kg payload can be accelerated to 50km/s to 80km/s over the span of 3 months, with a propellant consumption ranging between 0.25kg and 1kg per day.
http://www.niac.usra.edu/files/library/ … inglee.pdf
A. MagBeam for outbound transfer maneuvers (TMI / TEI)
MagBeam offloads most of the mass and power generating requirements for impulsive maneuvers to an orbital satellite / space station that supplies the input electrical power. MagBeam uses a plasma "gun" to remotely supply input power for propulsion, very similar to the beamed Microwave power concept, but with extreme beam coherence over great distances. The MagBeam spacecraft / space station stays in orbit around the planetary body and never leaves. The powered spacecraft uses the power beam to heat / ionize gas and generate a considerable amount of thrust over a very short time period measured in hours. This is the closest electric analog to an impulsive transfer that chemical or nuclear thermal propulsion provides. The MagBeam station's input power can be supplied by batteries, regenerative fuel cells, or nuclear reactors. I could care less which option is selected, so long as the station's mass remains within the realm of feasibility. What it does do is offload hundreds to thousands of tons of mass associated with the power generating equipment.
C. M2P2 for cruise propulsion and return to Earth (TEI only)
M2P2 alone is capable of producing very high velocities over a period of 1 to 3 months, tens of kilometers per second. It does have a specific impulse attached to it, because it requires the injection of a tiny quantity of gas each day, but that Isp ranges between 50,000s and 90,000s (not a typo). However, it was intended to function best in interplanetary space, away from the electromagnetic field of Earth's Van Allen belts. M2P2 uses an electromagnetically ionized plasma field to repel solar protons, generating thrust in the process. As the craft moves away from the Sun, the electromagnetic field inflates / grows larger in size, in order to generate near-constant thrust out to the Heliopause.
power sources for satelite
We're going to pursue using large numbers of Brayton-cycle Strontium Titanate Radioisotope Thermoelectric Generator. Instead of using very low efficiency TEG semiconductors, we're going to dump that in favor of using direct thermal power to spin an electric generator using a Supercritical CO2 (sCO2) working fluid. At 50% efficiency, we would require around 2,105kg of Strontium-90 to supply 1MWe. If we account for the 50% decline in thermal power output over 28.8 years, then we actually need 3,158kg of Strontium-90 to maintain at least 1MWe over the ship's expected service life of 25 years. Strontium Titanate (SrTiO3) is 5.11g/cm^3 / 5,110kg/m^3, so 0.618m^3 of active material. These devices reach temperatures near 800C, which is above the 725C to 750C required by sCO2 gas turbines to produce 50% thermal-to-electric efficiency in a 2 stage design.
Perhaps these documents will better explain what MagBeam is and isn't, and how it would be used:
Beam Propulsion by Chuck Vaughn
MagBeam by R. Winglee, T. Ziemba, J. Prager, B. Roberson, J Carscadden

Due to orbital mechanics and the altitude above Earth where the Van Allen belt radiation is most intense, no these MagBeam satellites will be located in LEO, not in a high orbit.
The key points to MagBeam are as follows:
1. The MagBeam satellites operate in LEO, where they are below most of the radiation form the Van Allen belts. Operating from LEO means the satellite only has to be lifted to LEO, which cuts down on propellant requirements.
2. When the MagBeam satellites fire the plasma beam into the magnetic lens aboard the ship, the two spacecraft are in close proximity and below the Earth's Van Allen belts, because the orbital modification of the ship is from circular to elliptical. It's not "spiraling out". The magnetic field is still present, but the plasma beam dispersion and distortion from being fired through the plasma / radiation field created by the solar's wind interaction with Earth's magnetosphere is considerably reduced.
3. MagBeam requires "fast discharge", but not "fast charge". This decreases wear and tear on the batteries, since both fast charge and fast discharge increase wear rates. I accounted for battery capacity by doubling up the mass allocated to batteries, such that we only have 50% Depth-of-Discharge for each "shot".
4. The entire impulse bit of 3km/s does not have to be provided at one time, which drastically lowers the stored power requirement. The satellite battery mass is then reduced to the amount of power that it can store and deliver to the payload / ship over a single orbit.
5. A series of MagBeam satellites / stations can keep the tonnage of individual satellites below the payload performance capabilities of a single Starship, so no orbital assembly is required and even if a catastrophic event disabled one of the satellites, all capability to launch is not lost due to a single catastrophic event.
We're deliberately providing impulse bits to the ship when it passes close by the MagBeam satellite. Let's say each satellite adds 0.1km/s of impulse to the outbound ship while it passes close by. The fact that it passes out of range is not an issue. You wait for another orbit, so that the MagBeam station has been recharged, and then deliver another 0.1km/s of impulse to the outbound ship. If you do it that way, then the powered ships requires 30 orbits or passes at the MagBeam satellite to supply the 3km/s of Delta-V required to achieve escape velocity. The orbit of the powered ship starts out being circular and then becomes progressively more elliptical with each impulse bit transferred by the MagBeam satellite.
The advantage is the 10,000s of specific impulse versus 450 seconds maximum for chemical or 1,000 to 5,000 seconds for arc jets or ion engines or electromagnetic thrusters like MPD or VASIMIR. VASIMIR can achieve 10,000s Isp as well, but it also requires onboard power and propellant. None of the power or propellant is stored aboard the powered ship or payload using the magnetized plasma beaming method, so it's even more efficient than any of those other methods.
The orbital velocity of the powered ship increases due to the "gravitational slingshot effect" of an elliptical orbit. In other words, velocity increases as the ship approaches periapsis and decreases as it moves toward apoapsis. My argument is that we're talking about a relatively minor interaction time delta. The ship's orbital velocity can never be equal to or greater than 11.186km/s, because that's escape velocity. Recall that we're using a number of MagBeam satellites (32 satellites in total) and that the discharge rate of the batteries can be varied over time, within reason. The initial interactions with the satellites will occur over a greater length of time, but then the discharge rate has to be increased to impart the same impulse bit over each interaction period. You lose 30% of your interaction time between 7.8km/s and 11.186km/s.

SpaceNut · 2022-01-02 17:39:36

The magnetic force needs multiple turns under a high voltage low current design to create the field
Amp * turns = one Gauss (B) is equal to one Oersted (H) in air.

So a rigid 1 turn needs high amperage to create the same field strength.

There are many more equations to solve for the values but the concept of the field is to bring the diffused received plasma into focus for thrust out of the engine after reflection.

The magnetic field can be created in the shape of a funnel by placing larger diameter rings at different distances from each other.

For lunar use I am not seeing any reason for AG as dipicted

SpaceNut · 2022-01-02 17:40:24

The receiver is a parabolic dish that reflects back a common beam...which the magnetic s control that beam after it gets beyond the focal point

https://en.wikipedia.org/wiki/Parabolic_reflector

this is similar to what we are doing with satellite TV dish.

The red is the incoming and the bounce is in gray to the feed horn which is replaced with the magnetic funnel.

SpaceNut · 2022-01-12 20:14:32

This is the opposite function but it shows how far we really need to make the power levels
Star Trek has tractor beams. So do we. But so far, they can't grab anything bigger than a dime.

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#1 2022-01-02 12:34:38

Mag Beam acceleration to/from lunar surface

#2 2022-01-02 12:40:03

Re: Mag Beam acceleration to/from lunar surface

#3 2022-01-02 13:12:43

Re: Mag Beam acceleration to/from lunar surface

#4 2022-01-02 17:39:07

Re: Mag Beam acceleration to/from lunar surface

#5 2022-01-02 17:39:36

Re: Mag Beam acceleration to/from lunar surface

#6 2022-01-02 17:40:24

Re: Mag Beam acceleration to/from lunar surface

#7 2022-01-12 20:14:32

Re: Mag Beam acceleration to/from lunar surface

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