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#1 2020-02-29 19:44:47

kbd512
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Registered: 2015-01-02
Posts: 5,868

electromagnetic launch with microwave propulsion

Louis,

There aren't 1 million people prepared to pay the cost of a house for a few minutes of suborbital flight.  If there were, then Virgin Galactic might be a trillion dollar company by now.  I can count the number of multi-millionaires who were willing to spend their money to go into space for any period of time on both hands.  The billionaires don't actually go into space.  They pay other people to develop space technology on the promise of an intellectual property payoff somewhere down the line.

If we combine electromagnetic launch with microwave propulsion to achieve orbital velocity, then the size / weight, therefore cost of associated flight hardware and intrinsic energy requirements to accelerate it to orbital velocity, comes down to something similar to an international cruise or airline flight.  At those prices, there may actually be enough customers to convince a corporation to maintain the infrastructure required.  The electromagnetic launch system is a glorified version of modern roller coaster technology on steroids and the entertainment business can afford that expense while remaining profitable.  The US government can easily afford electromagnetic launch and that's how we've decided to launch our fighter jets and drones from all future aircraft carriers, to include the Ford Class, which is already in service.

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#2 2020-02-29 21:22:04

tahanson43206
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Re: electromagnetic launch with microwave propulsion

Update 2020/03/20:  This topic has progressed nicely since it was opened in February of 2020.

Three primary technology options are under discussion, and four physical locations are in play:

Technology option 1: This was kbd512's original concept: Adapt US Navy electromagnetic catapult to accelerate vehicle to Mach 6
Technology option 2: use catapult technology to accelerate a passenger vehicle to Mach 1 or so
Technology option 3: (Edit:2020/03/21) Same as #1, but accelerate to near escape velocity.

Location option 1: Texas, in the Southeast, above Mexico
Location option 2: Mexico, in the Northeast, below Texas
Location option 3: Puerto Rico, which has a deep ocean trench to the West where a launcher could be submerged
Location option 4: Indonesia, which has recently announced intentions to launch a satellite in five years

There are many technical hurdles to overcome for each of the technology options.
There are economic, social and political challenges for all options.

Of particular interest to me in mid-March of 2020, is finding a solution to the sonic boom problem for high speed launch at the surface of the Earth.

Beyond that, discovery of potential to extend the US Navy catapult technology (or rail gun technology) into this realm is necessary.

Edit(2020/03/22) See Post #5 of this topic for details about how kbd512 would direct a project to build an EML.

Edit #2: 2020/03/30 kbd512 provided support for the use of LOX.  However, for a vehicle to be launched from an EML, I think that a propellant combination that requires less fussing prior to launch would be more practical, and in the end, more cost effective.  At this point, I am leaning toward Dr. John Hunter's preference for a solid fuel rocket for orbit circularization, and some liquid method for docking maneuvers.

Original message from 2020-02-29 21:22:04 is saved below:

For kbd512 re #13 and electromagnet launch ...

I'm sure you know about previous work on this technology, but new forum readers may not have read as much as you have.

There are some interesting citations at the top of the list Google creates for "electromagnetic launch mountain"

In addition, I was happy to see a number of citations about the military developments you cited in Post #13.

A good place to put an electromagnet launcher is on a mountain side near the Equator.

Enclosing the track inside a modest weather shield would improve prospects for reliability of service.  At the same time, it would reduce chances of wildlife intruding on the track or producing unwanted changes to the equipment.

As you probably noted, Calliban recently proposed electromagnetic track launch for payloads from the Moon.

(th)

Last edited by tahanson43206 (2020-03-30 09:09:22)

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#3 2020-02-29 23:41:44

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

The US Navy routinely uses EMALS (ElectroMagnetic Aircraft Launch System) to send F/A-18E/F/G Super Hornets and F-35C Lightning II (America's tri-service stealth tactical strike fighter) off the deck of the USS Gerald R. Ford class nuclear powered aircraft carriers.  Although there were developmental issues with this steam catapult system replacement, all indications are that these engineering problems have been satisfactorily resolved at the time of this post.  Any new technology developed by DoD always has its share of development problems.

The US Navy EMALS requires roughly 300 feet to accelerate a 100,000 pound aircraft to 150mph.  Many moons ago when A-3D Skywarrior tankers and F-14 Tomcats (the more practical but still troublesome replacement for the ill-fated F-111B fleet interceptor), 100,000 pounds was about as high as you could go using steam catapults and it set a minimum launch weight for these aircraft catapult systems that was incompatible with smaller aircraft such as drones.  In practice, all of our fighter jets generally weigh between 50,000 and 60,000 pounds at launch (if they're laden with a prototypical combat load out of fuel and ordnance), but drones can be considerably lighter and that's a problem for steam catapults.  Roughly speaking, naval aircraft catapults (whether steam or electrical) provide a 3g acceleration from a dead stop to 135 knots (we always put 30 knots of wind over the deck by turning the carrier into the wind for launch and recovery; nearly all aircraft carriers with catapults for launching tactical fighters do this, to the point that it's almost a rule, and it's a function of minimum takeoff / landing speeds for supersonic fighters).  In any event, this requires 136kWh (4 gallons of gasoline worth of electricity released in 2.2 seconds or thereabouts) of energy and is in excess of what the electrical power transfer subsystem of the 700MW onboard nuclear power plant can provide.  To get around this limitation, 4 spinning rotors (electrical energy stored as kinetic energy in a flywheel) are "charged up" by spinning them up to speed between aircraft launches.  That process takes less than a minute.  On that note, I can't think of any reason why a 10g acceleration of a drone aircraft would not be feasible, especially if it was built to be sturdy enough to accelerate to hypersonic velocity at sea level.  The Orbital ATK Cygnus Pressurized Cargo Module survives the sustained 8g acceleration of launch using Orbital Sciences Antares rocket.

Spinning up flywheels is actually faster than generating enough steam pressure in a conventional steam catapult system (what all the Nimitz class nuclear powered aircraft carriers that I served aboard used), so the launch rate is higher.  By the time an aircraft is actually ready to launch (positioned in front of a catapult, connected to the catapult, launch weight verified, arming pins removed from ordnance, the jet blast deflector raised to launch position, the engines run up to full power, and flight controls checked), the EMALS Cats ("cat" is short for aircraft catapults, or at least that's what we called them when I was in the Navy) are ready to fling another fighter jet off the bow of the ship.

Long story short, 4 gallons of "gas" (in terms of electrically "spun-up" mass converted to electrons) is about as good an energy trade for accelerating 100,000 pounds of aircraft to 150mph as anything I've ever seen or heard of.  The system doesn't care what provides the juice, either.  Whether it's solar, wind, gas turbine, or nuclear makes no difference at all.  If you spin up enough flywheels to dump the power required in a very brief period of time, then you can electromagnetically launch just about anything.  This is also not the kind of insane multi-thousand-gee acceleration you get from gun launch of any description, so the wear and tear on the catapult components and aircraft / payload is minimal as long as you suppress any arcing and sparking in the motor and use magnetic bearings for the flywheels.  EMALS is just an application of a linear induction electric motor and it achieves the efficiency of induction motors so far less power is converted to waste heat, as in a rail gun or coil gun or light gas gun.  As with anything else, there are limits.  That said, a rocket powered drone with a hypersonic launch velocity is entirely within the realm of feasibility and then the total propellant tonnage required to attain orbital velocity looks a lot less problematic from the standpoint of including enough structural design mass in the vehicle to make it truly durable / reusable.

I approach this from the standpoint of achieving high flight rates with vehicles that closely resemble large fighter jets.  We do that by providing the initial acceleration to hypersonic velocity to eliminate the requirement for a booster and then we can use very conventional LOX/RP-1 propellants in practical single-stage-to-orbit vehicles with a payload that represents a significant fraction of the total wet mass of the vehicle.

Microwave propulsion is a very technical subject, but if the combination of electromagnetic launch was combined with microwave propulsion, then the propellant mass would be no greater than the internal fuel carried by a typical fighter jet to deliver a similar payload mass fraction that a fighter jet would carry to orbit.  Most of our modern fighters weigh about 15t empty, carry a 10t payload, and use 10t of gas per flight.  If we could achieve that kind of efficiency for orbital flight, there'd be no practical issues with constructing real "starships" with masses similar to that of a battleship or small aircraft carrier.  These are the kinds of "real ships" needed to colonize other worlds and make living and working in space a practical proposition for some statistically significant portion of Earth's total population.

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#4 2020-03-01 08:11:22

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re #15

You've provided a solid base for development of capability by members of this forum.

I have no idea what you might assign to workers if you could enlist them to help you.

The microwave support capability seems a bit of a stretch to me right now.  Folks have been talking about that for quite some time, and some of the proposals I've seen have been reasonably detailed.

What I think is feasible shorter term is giving a fully fueled passenger space vehicle sufficient impulse from a ground launch to reach LEO.

Thanks for your detailed explanation of the rotating mass energy storage and rapid dump system!  Again, it's one of those technologies that's been discussed for decades if not longer, but your report on implemented solutions is bringing me up to date in a hurry.  Hopefully I am not the only forum reader who finds your update encouraging!

Please consider listing tasks (or perhaps categories of effort) that you would assign to assistants if you had an unlimited (Pentagon scale) budget.  Some of them may appeal to current forum members.. Equally importantly, they could provide incentive for forum readers with the matching education, skills, talent and available time to donate some of that time to solving one or more of the tasks.

You could (should you so choose) help by setting goals you would like to see achieved.

Launch of a small space capable self-return vehicle with a couple of passengers seems to me to be a realistic goal.  The market could be a single NASA astronaut to be delivered to the ISS by a vehicle with a single onboard pilot.   Several small vehicles that fit this description are already in service or in advanced stages of development.  The little X37 is a very good example.  It would need a second stage booster, but the electromagnetic launcher you've envisioned should be able to give the X37 with booster a first stage equivalent momentum.

In your detailed reply you did not address the issue of the launch at an angle, but I'm assuming that is because you had more fundamental information to impart.

Edit#1: Since this is the "Tourism" topic, I'll add that the passenger could be a wealthy civilian, interested in either just an orbital flight, or a visit to a station in LEO.

(th)

Last edited by tahanson43206 (2020-03-01 08:13:35)

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#5 2020-03-01 20:08:43

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

If I was leading a project, which I'm not, there are three fundamental engineering issues to tackle.  The first is power delivery.  The second is dumping waste heat.  The third is stabilizing the vehicle as it travels down the track and during release.  Beyond that, it's mostly basic electrical engineering and motor design.  There's not much in the way of creativity required, given the current state-of-the-art in electric motor design.  Furthermore, the purpose of this project is to showcase the results from a practical engineering effort intended to reduce launch costs, rather than how extremely efficient some overly-engineered solution might be if cost was no object.  If achieving Mach 5 is impractically expensive, but Mach 4 requires no new materials or special launch preparation requirements, then we design for Mach 4 and resign ourselves to making up for that dV loss elsewhere.

As far as launch angle and identification of suitable sites to build the infrastructure are concerned, I'd choose a flat and level desert far away from major population centers and wildlife that might interfere with launch.  The system should also be robust enough to pulverize the odd buzzard, when such an unfortunate circumstance occurs, without suffering a catastrophic failure.  Maybe that sets practical upper limits on launch speed or overall efficiency, but so be it.  The rocket would use aerodynamic lift to depart the launch track.  The use of microwave propulsion need not be invoked to achieve the same fuel economy result using a combination of electromagnetic launch, air breathing propulsion (the British SABRE system immediately comes to mind), and rocket propulsion (SABRE combines air breathing and rocket propulsion, BTW).  However, this dream of Mars colonization that Elon Musk wishes to achieve won't come to fruition without a dramatic reduction in launch vehicle wet mass and therefore fabrication and ongoing operational costs.

It should also be understood that if I'm running the project, we're adhering to a schedule and a budget.  I'm not about to start issuing blank cheques to government contractors.  I'll hire or fire whomever I need to, in order to ensure that the project continually moves forward.  If a contractor doesn't deliver, then the terms of the contract would dictate that they forfeit any profits from expenses that I, the government project manager, incur as a result of their failure.  USAF General Bogdan eventually had to resort to that tactic on the F-35 project, but that's my starting point.  This is an engineering exercise, not an exploration of new technology possibilities at tax payer expense.  The justification for the project is dramatically reducing costs incurred by the tax payer for all space launch activities through investment in the launch infrastructure.  We've clearly not been able to dramatically reduce launch costs associated with conventional rocketry, so this is the next logical step.  If I can't find any contractors willing to "stand and deliver", then I'll happily use university engineering students who are only interested in actually achieving a worthwhile result.  I might offer to pay their college tuition and expenses in exchange for delivering the results I require.  That may be more effective than employing traditional government contractors.  A separate team would be responsible for vehicle development.  I'm only there to deliver the catapult system, not the entire solution.

I feel as though we need to begin by setting a few key system performance requirements up front:

* Maximum launch vehicle tonnage
* Maximum launch vehicle acceleration rate
* Maximum launch velocity
* Maximum launch rate
* Minimum track length required to bring the launch vehicle to a halt if the onboard engines fail or a launch track power supply fails
* Minimum supplied power requirements to deliver the power required
* Motor technology - it's worth noting that linear synchronous motors tend to be more practical for higher speeds than linear induction motors because they have higher efficiency in certain operating speed regimes and lower mass that makes induction motors impractical past a certain speed (I'm not married to any particular motor technology, I just want the pros / cons of each thoroughly researched and then the most appropriate technology selected on the basis of practicality and therefore cost)
* A first generation system will be designed exclusively for cargo delivery and after thousands of launches have been successfully conducted and we thoroughly understand the maintenance issues from several years of operations, only then will we commit to launching humans
* Our initial design goal is a marginal cost of $20/kg over 3 years of operations, exclusive of the R&D and construction costs (eventually, this system should pay back all of the R&D and construction budget as well)
* I think the initial delivered payload target should be 50t and we'd launch once per hour during daylight hours to take advantage of solar power in the desert (146,000t of payload per year), with the eventual goal of achieving flight rates similar to an aircraft carrier (one launch every 5 minutes (1,752,000t of payload per year)
* We'd use desalinated sea water to provide the LOX/LH2 propellant (a must to achieve a high launch rate)
* If greater delivered payload tonnage is still required, as it eventually will be, then our government can build additional launch tracks at other suitable sites, perhaps a mountain track for experimentation purposes or polar orbits and one on both coasts

More about the design and its potential benefits:

The US Navy experimented with linear induction motor electromagnetic launch systems to fling B-25 bombers off the end of short island runways as far back as WWII.  The system from that era was called the "electropult".  The engines installed in the bombers of that era weren't powerful enough to takeoff from the short runways associated with the island hopping campaign in the Pacific when fully laden with fuel and bombs.  Rather than giving up fuel or payload, the Navy decided that giving aircraft an assist to achieve flying speed was a better solution.  While we have no such issues with generating enough raw thrust today, the fuel economy of rocket engines for orbital launch vehicles leaves a lot to be desired.

This NTRS paper link shown below is a good primer on what a first generation electromagnetic catapult system using linear induction motors could provide in terms of "virtual gain" in specific impulse.  Merely using their existing and very simplistic prototype was sufficient to add almost 30 seconds of "virtual Isp" to a rocket by means of accelerating the rocket to Mach 1 before it left the catapult track, thereby saving the propellant required to accelerate to Mach 1.  The vehicle and rocket fuel mass that would've otherwise been required to achieve Mach 1 was thereby eliminated by starting with an initial velocity of Mach 1 via electromagnetic catapult launch assist.  The various tables in the paper show just how dramatic the reduction in launch mass can be when electromagnetic launch assist is combined with air breathing propulsion.

First Stage of a Highly Reliable Reusable Launch System

Look at Table 2 on Page 7.  For sake of comparison, they used the Gemini orbital launch vehicle.  Notice how supplying a minor fraction of the initial dV increment affects the mass of the first stage.  Launch assist to Mach 1.5 combined with air breathing propulsion to Mach 4 cuts the total wet mass in half.  Note how little improvement was provided by air breathing propulsion to Mach 10.  Now think of how little incentive there is to do anything but electromagnetic launch to Mach 4 or so, followed by conventional rocket propulsion to orbital velocity using fuel efficient LOX/LH2.  It should be noted that it doesn't matter what the launch system is or how great, or not, the specific impulse of the conventional rocket stage components happens to be.  You get an associated percentage decrease in stage mass and size no matter what rocket stage propellants are selected.  However, it still makes sense to make the upper stage wet mass as low as possible.

Imagine for a second that we wanted to electromagnetically launch all 11,000,000 pounds of Starship Super Heavy booster plus upper stage plus payload to Mach 1.5.  At $0.10 per kWh, that works out to a launch "fuel" cost (electrons generated by "some power source") of $1,718.75.  Starship could feasibly deliver 1,000 passengers to orbit per flight assuming that the average passenger plus consumables mass is 100kg (this is a ferry flight for immediate transfer to a real space station or real interplanetary transport), even with conventional vertical launch.  However, using electromagnetic launch to achieve Mach 1.5 represents a total "fuel" cost per flight of $1.72 per passenger.  I don't care if LOX/LCH4 is only $1 per gallon landed cost (meaning total cost delivered to the rocket's propellant tanks from wherever it was produced), that's an enormous increase in fuel efficiency and it allows the booster propellant tanks to shrink accordingly.  Even super ultra premium electrons sourced from German solar power farms would only increase the launch cost by $2 per passenger.

Imagine a rocket with the same payload capability as Starship that only weighs 5,500,000 pounds by using electromagnetic acceleration and a modest form of air breathing propulsion.  If anyone else is counting, that cuts our electron fuel costs in half.  After we're done eliminating the booster entirely using electromagnetic acceleration, our revised Starship weighs 2,900,000 pounds with its load of 2,600,000 pounds of LOX/LCH4 propellant.  Our payload mass fraction is still just 1/29th of the total wet mass as compared to 1/110th, but that's nearly 4 times better than it would otherwise have been.  If SpaceX switched to LOX/LH2 propulsion, the payload mass fraction would be 1/11th of the total wet mass, or 10 times better (less than 1,000,000 pounds of propellant versus 9,900,000 pounds of propellant).

LOX/LH2 is not 10 times more expensive than LOX/LCH4.  LH2 is about $3 per gallon.  LCH4 is about $2.66 per gallon.  There is no merit to the fuel cost argument when you're using 10 times less fuel to achieve the same result.  Combining electromagnetic launch with microwave propulsion would yield a propellant mass no different than a commercial airliner, meaning the majority of the total vehicle mass is structure and payload.  In any event, $1,000,000 per flight in terms of fuel costs is achievable without invoking microwave propulsion.  That's 1,000 per ticket.  If the vehicle and infrastructure maintenance costs another $1,000 per ticket, we've arrived at something very closely approximating an international flight between continents.  I figure the government can foot the bill for the R&D of the launch system and then everyone gets to use it for a comparatively modest maintenance fee, no different than renting launch pads at our existing space launch complexes.

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#6 2020-03-01 21:07:19

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re #5

OK ... Post #5 is going to take a while to study.  I scanned it, and appreciate your addressing the slope question.

A horizontal takeoff from a desert location seems a lot more likely to pass zoning review than any mountain side in the United States.  I took a quick look at mountains in Texas (there are none where I live) and found that every mountain in Texas is beloved of naturalists and outdoors folks and ANY industrial activity would be resisted, let alone a launch track on the scale we are discussing here (or any scale, for that matter).

Here is an article from 1982 that may contain something useful for the current discussion.  It did anticipate a launch at an angle to reach LEO, and a vertical launch to leave Earth altogether.

https://ntrs.nasa.gov/search.jsp?R=19820021469

An Earth to space electromagnetic (railgun) launcher (ESRL) for launching material into space was studied. Potential ESRL applications were identified and initially assessed to formulate preliminary system requirements. The potential applications included nuclear waste disposal in space, Earth orbital applications, deep space probe launchers, atmospheric research, and boost of chemical rockets. The ESRL system concept consisted of two separate railgun launcher tubes (one at 20 deg from the horizontal for Earth orbital missions, the other vertical for solar system escape disposal missions) powered by a common power plant. Each 2040 m launcher tube is surrounded by 10,200 homopolar generator/inductor units to transmit the power to the walls. Projectile masses are 6500 kg for Earth orbital missions and 2055 kg for nuclear waste disposal missions. For the Earth orbital missions, the projectile requires a propulsion system, leaving an estimated payload mass of 650 kg. For the nuclear waste disposal in space mission, the high level waste mass was estimated at 250 kg. This preliminary assessment included technical, environmental, and economic analyses.
Publication Date:    June 30, 1982

In general terms, I ** do ** think your proposal to use winged vehicles for the lower stages of flight would "just sound safer" to potential customers.  However, flying with a fully loaded second stage booster might be a bit more risky than taking off with a full tank of Jp4 as we do routinely today.

(th)

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#7 2020-03-02 01:04:59

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

Wings obviously don't contribute much to upper stages except structural mass, as Elon Musk correctly noted, but an air breathing booster that uses a ramjet or special purpose jet engine such as SABRE would unequivocally best the specific impulse of the LOX/LH2 rocket engines and LH2 solid core nuclear thermal rockets by a significant margin.  SABRE's specific impulse is 3,600 seconds at sea level, but drops to 460 seconds as the propulsion system transitions to pure rocket thrust when the air becomes too thin.

The best solid core nuclear rocket engines were only around 900 to 1,000 seconds and their thrust-to-weight ratio is not significantly better than a jet engine.  A microwave beamed propulsion system would offer a thrust-to-weight ratio somewhere between a jet engine and conventional LOX/LH2 rocket engine, the specific impulse advantage of NTR, require no onboard oxidizer or associated turbo pumps, and of course, it would not have an operating nuclear reactor onboard.  NERVA heated the LH2 from -260C to 2,200C.  One of the 1MW gyrotrons developed for the ITER project heated Aluminum metal to 10,000C to vaporize it and produce thrust.  A gas core nuclear rocket would operate at about 25,000C for comparison purposes, corresponding to specific impulse ranges between 3,000 and 5,000 seconds, meaning beamed microwave propulsion used to vaporize Aluminum "fuel" (rather than heat LH2 using a heat exchanger) could closely approximate the specific impulse of a vapor core or "nuclear lightbulb" (closed cycle gas core) nuclear thermal rocket.  This would obviously be a technological windfall for more economical space flight, but the fuel mass reduction benefits of electromagnetic catapult assisted launch would remain for uses here on Earth and on the moon or Mars.  Anyway, the beamed power system is "next 20 years" type stuff, whereas ramjets or SABRE is "next 5 years" type stuff.

SABRE is novel British jet / rocket engine that uses a special heat exchanger / pre-cooler to drop the incoming air temperature from 1000C at Mach 5.5 to -150C in 1/20th of a second.  DARPA provided the money to build the test facility for the heat exchanger core and construction of the test facility started in 2018.  Although testing is ongoing, the pre-cooler has already been proven through testing to actually work (drop the temperature from 1000C to -150C in 0.05 seconds, that is) and the heat is dumped into the LH2 fuel just before it's fed into the jet / rocket engine combustion chamber, where it contributes to the extreme pressure ratio that makes the engine so fuel efficient.  Most of that sea level / low speed efficiency is lost as speed increases and air density drops as altitude increases.

If you read that NTRS document I posted a link to, the ramjet booster mass reduction associated with Mach 4 vs Mach 10 propulsion is very limited and mostly speculative in nature since we don't have any working Mach 10 scramjets.  Even flying though the rarefied air of the upper stratosphere at hypersonic speeds for any significant period of time requires massive quantities of fuel, so the massive increase in thrust that a rocket engine can provide as compared to air breathing propulsion to overcome drag and gravity losses starts to win out.  However, it's equally obvious that rocket engines are absurdly inefficient for accelerating to prototypical booster burnout velocity.

Falcon 9's first stage booster burnout velocities range between Mach 4.85 and Mach 6.7, which is mostly within the realm of existing ramjet engines.  Ramjet efficiency starts to drop as you approach Mach 6.  Theoretically, scramjets could provide better efficiency up to Mach 10 or so.  However, their efficiency also starts to drop and the specific impulse looks a lot like NTR or beamed microwave propulsion at that point.

Perhaps some combination of ramjet and scramjet technology would ultimately win out over hybrid jet / rocket engines like SABRE.  If we push launch speeds to Mach 2, there may not be enough acceleration time to merit something as complicated as SABRE.  By Mach 3, there's not much that SABRE does that a ramjet couldn't do with greater simplicity and comparable efficiency.

Our own GW Johnson is the man I'd select for designing the booster since that's what he did for his entire career.  He has a good write-up on these technologies here:

An Ex Rocket Man's Take On It: December 2016

I'd say I need a ramjet booster to operate between Mach 2 and Mach 6 to completely replace the rocket booster following a Mach 2 liftoff from the catapult.  This is preferable since there are far fewer moving parts in a ramjet than a gas turbine / rocket engine like SABRE.  A LOX/LH2 upper stage would supply the rest of the dV increment required to achieve orbit.  If it's possible to electromagnetically accelerate to Mach 5 or Mach 6, there's probably no benefit at all to using a booster of any kind and we'd be much better off using conventional rocket propulsion.

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#8 2020-03-02 02:17:02

kbd512
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Re: electromagnetic launch with microwave propulsion

Also of note is how electromagnetic catapult assisted takeoff could allow airliners to operate from shorter runways:

Thermal Design of Linear Induction and Synchronous Motors for Electromagnetic Launch of Civil Aircraft

A technology that benefits military / naval aviation, civil aviation, and space launch would be highly desirable.

Here's my source for alternative fuel prices, not including Hydrogen, for which I used figures paid by NASA for their LH2:

US DoE - 2018 Clean Cities Alternative Fuel Price Report

As space travel becomes an increasing portion of our economy, we need to at least consider ways to minimize rocket fuel consumption and the benefits from burning cleaner but more energetic fuels such as LH2, if only to reduce the cost of space flight to something that the average person can afford.  The fuel consumption associated with catapult assisted launches should be half that of pure rocket propulsion and perhaps a quarter if the booster can be eliminated entirely.  The cost of the electricity doesn't even rise to the level of noise by way of comparison.  To "launch a thousand ships", as Elon Musk spoke of doing, we're talking about multiple billions of dollars in cost savings, especially if the upper stage is fueled with LH2.  That may only be pocket change to our federal government, but still real money in the realm of business and personal finance.

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#9 2020-03-02 07:13:20

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re #8 and topic

A feature of US Navy ship mounted electromagnetic catapult systems is the use of wheels on the aircraft to bear the weight of the aircraft.  In your vision of similar systems for civilian aircraft or for space bound vehicle combinations, you may well have had that feature in mind all along.  This post is offered as a reminder that not everyone has the same vision, so a clarification of your vision on that point would be helpful.

There are some alternate designs that involve the launcher bearing the full weight of the payload package, which would vastly increase the cost of the catapult system, which is already going to be massive and complex just to pull a wheeled vehicle to takeoff velocity.

Your suggestion of acceleration of a vehicle (wheeled aircraft bearing rocket as payload) to Mach 5 or 6 suggests (to me at least) building the launcher in a location that allows flight over a body of water, such as the Gulf of Mexico.  The sound effects to be expected from launch at those speeds will be significant, and performing that operation over water would seem reasonable.

Another advantage of launching over the Gulf of Mexico is that the aircraft can perform the fine tuning of matching the desired orbital plane before the rocket payload ignites its fuel and begins the second stage burn.  Thus, the facility can serve multiple customers with multiple launch requirements.

I brought up a small map of Texas and note there (may) be stretches of coast line suitable for construction and operation of a large scale catapult system.

Among other advantages of this potential siting is the possible availability of land for solar panels to collect energy for the rotating mass energy dump systems I am extrapolating from your description of the US Navy carrier catapult systems in use today.

It should be noted that if my theory of wheels bearing the total weight of a vehicle to be launched is correct, then the runway will necessarily be constructed to support that weight, which implies significant investment in that component of the complete system.

I presume the empty aircraft carrier vehicle can land anywhere, since it's mass would be reduced to just it's own airframe after releasing the rocket component.

(th)

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#10 2020-03-02 09:13:50

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

The electromagnets will have to bear the weight of the vehicle, no different than the various MAGLEV trains, which have already been proven to work at high subsonic and low supersonic speeds on test tracks.  There's no such thing as "raising the landing gear" at Mach 1, never mind Mach 6.  The launch vehicle would attain flying speed before leaving the track.  Electromagnetic locking mechanisms will secure the vehicle to the trolley and therefore track during the acceleration phase and then release it after final target velocity has been achieved, or keep it connected to the track and bring it to a halt if the target velocity hasn't been achieved.  The landing gear for the launch vehicle and booster (if still required) will be conventional gear, but would only be used for landing, no different than the various other winged lifting bodies of our space program.  No "wheel reinvention" will occur on this project.

In simple terms, a trolley with electromagnetically operated connection points is secured to pins built into the lifting body.  After launch velocity is achieved, those electromagnets release, the launch vehicle flies away from the track under power using its own rocket engines or ramjet booster, and the trolley is electromagnetically slowed to a halt.  This is not going to be some minor variant of an existing system.  It's going to be fairly big out of necessity, and yes, that will increase its cost.  The upside is that anyone with a compatible launch vehicle can use it and the force generated by the electromagnets is controllable so a wide range of payload tonnages can be accelerated appropriately.  The utility of the US Navy variant of this type of system is its ability to accelerate very light or very heavy aircraft with significantly less stress on the airframes than steam catapults produce on account of the much smoother acceleration curve.

The goal is prototypical booster burnout velocity, followed by pure second / upper stage acceleration to orbit using rocket propulsion.  If a ramjet booster is required, so be it, but then we have two different craft that need to land somewhere downrange.  I'm aiming for Mach 6.  There's no reason a single stage can't make it to orbit with a significant payload fraction at that point.  The 50t payload was an aspirational goal.  Perhaps 10t payloads are more realistic.  At the end of the day, I want a fleet of launch vehicles delivering consumables / raw materials / small finished parts / small satellites to orbit and leaving the station like clockwork aboard simplistic vehicles that deliver the payloads to LEO / de-orbit / land / nothing else.  It's like a shipping business with hundreds of small cargo trucks.

Edit:

Faster launch cycles / less turnaround time may favor even smaller payloads, such as 5t or so.  I'm not sure of what the right solution is, but I know that elimination of the booster is part of the answer to reducing flight costs.  As Elon Musk often points out, the booster represents at least 2/3rds of the cost of the entire rocket in terms of hardware and launch costs.  If you can get rid of that, then you really have something special.

Last edited by kbd512 (2020-03-02 09:19:26)

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#11 2020-03-02 12:15:59

Calliban
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Re: electromagnetic launch with microwave propulsion

Kbd, this is an excellent thread with some fascinating analysis and ideas.  Note, that a rocket sled currently holds the land speed record of Mach 8.5.  This bounds the Mach 6 take off speed that your concept aspires to.
https://en.m.wikipedia.org/wiki/Rocket_sled

This did not require maglev, just very straight rails and a coupling that held the vehicle onto the rails.  But maglev may be a requirement for what you have planned, as the amount of wear at Mach 6 could be excessive if heating leads to surface oxidation.  Maybe graphite grease would allow the use of ordinary rails?  I don't know.

If the plan is to accelerate the vehicle with only a slim angle w.r.t horizontal, then most of the track could be beneath ground.  A few scoping calcs for a 20km long track, with final velocity Mach 6 (2km/s).  Acceleration would be 10g -which is tolerable for human payloads.  Acceleration time would be 20 seconds.  Kinetic energy of vehicle would be 2MJ/kg.  The SpaceX Starship upper stage weighs 3500t, so total KE is 7000GJ.  Total end use power is 350GW.  If we assume that the motor is about 50% efficient, then power requirements are 700GW.  That exceeds the power generating capacity of the entire US.  But it could be delivered by large banks of open cycle gas turbines.

According to this site they have capital cost of about $400/kw.  The turbines could charge a set of fly wheels (this could be done electrically or by direct mechanical coupling I.e. fluid coupling).

Last edited by Calliban (2020-03-02 12:30:26)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#12 2020-03-02 12:54:54

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re topic ...

Please spend a moment or two thinking about location for the system you are proposing.

Calliban introduced a new element to the discussion, with the suggestion part of the track might be underground.

I suspect there are two different mental pictures at play here.  I'm thinking of a huge flying vehicle able to carry the mass of a fully loaded Starship second stage on its wings, with sufficient extra strength to bear the stress of curving the flightpath toward near vertical.

Please clarify your mental model of the proposed system.

***
Thanks for your clarification that your concept would place the entire mass of the vehicle and the Starship on magnetic lift.

FYI ... amusement parks provide a useful example of practical implementation of linear motors for transport of humans safely.

The example I have seen had strong metal wheels rolling on a heavy metal track.  Propulsion was provided by linear motors, as stated.

I have not checked maglev train technology as developed in Japan or China, but I'll bet that steel wheels are part of the package, to carry the mass at stations and in emergencies when the train has to stop mid-flight.

In order for this topic to persist much longer, it will be helpful to recruit people with the appropriate education, skills, experience and generosity of spirit to allow an Open Source initiative like this to persist beyond the initial vision stage.

There exists a new topic intended to provide a place for suggestions for text for outreach efforts.

(th)

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#13 2020-03-02 13:27:44

louis
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Re: electromagnetic launch with microwave propulsion

I think it's more realistic to think in terms of single person carrier/satellite launch craft. An SPC might weigh in at little more than 100 kgs. Your life support can be very basic while make the relatively short journey to orbit, where you might dock with a Mars or Moon-bound Starship. If there's a failure, a parachutre system deploys.

tahanson43206 wrote:

For kbd512 re topic ...

Please spend a moment or two thinking about location for the system you are proposing.

Calliban introduced a new element to the discussion, with the suggestion part of the track might be underground.

I suspect there are two different mental pictures at play here.  I'm thinking of a huge flying vehicle able to carry the mass of a fully loaded Starship second stage on its wings, with sufficient extra strength to bear the stress of curving the flightpath toward near vertical.

Please clarify your mental model of the proposed system.

***
Thanks for your clarification that your concept would place the entire mass of the vehicle and the Starship on magnetic lift.

FYI ... amusement parks provide a useful example of practical implementation of linear motors for transport of humans safely.

The example I have seen had strong metal wheels rolling on a heavy metal track.  Propulsion was provided by linear motors, as stated.

I have not checked maglev train technology as developed in Japan or China, but I'll bet that steel wheels are part of the package, to carry the mass at stations and in emergencies when the train has to stop mid-flight.

In order for this topic to persist much longer, it will be helpful to recruit people with the appropriate education, skills, experience and generosity of spirit to allow an Open Source initiative like this to persist beyond the initial vision stage.

There exists a new topic intended to provide a place for suggestions for text for outreach efforts.

(th)


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#14 2020-03-02 21:34:33

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

I was thinking of something similar in appearance to Orbital ATK's Pegasus booster (the delta wing lifting body portion of the launch vehicle; was also used as the booster for NASA's X-43A hypersonic test vehicle), but larger and using LOX/LH2 vs solid rocket propulsion to achieve orbit with a substantial mass fraction available for the payload.  It would be electromagnetically accelerated to Mach 6 using some type of MAGLEV type track and LIM or perhaps LSM technology.  In terms that more people might understand, the launch vehicle would look something like the USAF's now-retired Convair F-106 Delta Dart interceptor, but with a thinner wing profile of the hypersonic Pegasus booster and no air intakes, obviously, since we don't have any non-experimental Mach 6+ propulsion systems apart from rockets.  All indications are that the value-add for air breathing propulsion at that velocity is minimal and the thrust that rocket engines provide is more important than the marginally better fuel economy / specific impulse of a scramjet.

The delta wing is what ATK refers to as the "strong back" (the attachment point between Pegasus and its airborne launch vehicle).  In this ground-launched variant, the strong back would be facing downwards and connected to the MAGLEV trolley.  When it flies off the track it'll look much like a F-106 takeoff, apart from the fact that the landing gear would already be retracted and it's already moving more than twice as fast as the F-106's top speed.  During a launch, the tiny "wing" would have already developed more than enough lift to depart the track before it reaches the end of the track.  That's why an electromagnetic clamp or claw is required to release the vehicle.  The launch vehicle is trying to rip the trolley off the track (very little of the trolley is above the track, most of it being electromagnetically "centered" or "sandwiched", if you will, between a series of 4 powerful acceleration / guide electromagnets that surround the trolley on all four sides (note that numerous other electromagnet configurations are possible and again, I'm not married to some specific technology or idea about how this will work- whatever is most practical wins, period), with just the claw (four semi-circular hooks that rotate using electromagnetic force to engage / disengage from the launch vehicle to release it) connected to the launch vehicle above the track, much like a traditional aircraft carrier catapult), so quite a bit of force is required for positive separation / instant retraction of the "claw" that has ahold of the pins on the strong back (the belly of our little rocket plane).

Site Selection:

Some place that ends up in a large body of mostly uninhabited water, such as the Gulf of Mexico, would be ideal.  However, the aerodynamic forces involved with a Mach 6 sea level launch should act to quickly break apart the launch vehicle if it doesn't fly about as straight as a laser beam on its launch trajectory.  Apart from electromagnetic deceleration, this launch method is not inherently any "safer" than a conventional rocket launch, but there's a lot less propellant involved and the vehicle is a lot smaller, so we have that going for us.

We do need a straight shot, multiple kilometers in length, preferably sitting on very solid bedrock.  The launch track will be contained in a concrete revetment so that when a catastrophic failure occurs on the launch track, there's a good chance that the revetment will contain debris from the launch vehicle.

Calliban,

Apart from the trolley's connection to the launch vehicle's wing / strong back, nothing will make significant contact between the trolly and the electromagnet assemblies.  A series of spring-loaded guides will prevent the trolley from contacting the electromagnets, but the centering force will be provided by the electromagnets on all sides.  As previously stated, the launch track will be dug into the ground to protect the rest of the facility from failures, but would not be below ground / subterranean.

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#15 2020-03-02 22:32:40

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re #14

Thanks for clarifications and developments of your vision for this system.

And ** thanks ** for pinning down the Gulf of Mexico as a potential safe overflight surface for this vehicle.

The public use of that space will justify some thought about the sound signature of the package.

Your plan for a near horizontal trajectory, with a very small angle of attack, suggests a long run at high mach numbers that implies (to me at least) that you are planning to gain elevation due to the curvature of the Earth.

The previous work done exploring this launch method (as shown by links in earlier posts) anticipated high angle of attack for the track, including true vertical for some implementations.

I'm conflicted a bit over the launch angle.  The idea of following the surface of the Earth is appealing, for a number of reasons, but the very low angle of attack is unusual, so I'm looking forward to seeing your thought process as you work through the flight plan.

Some place that ends up in a large body of mostly uninhabited water, such as the Gulf of Mexico, would be ideal.  However, the aerodynamic forces involved with a Mach 6 sea level launch should act to quickly break apart the launch vehicle if it doesn't fly about as straight as a laser beam on its launch trajectory.

Is Texas a candidate location for this concept?

There is a bit of grumbling about Elon Musk building prototype Starships on the Texas coast, but so far there haven't been any takeoffs to shake the windows.

The electromagnetic launch system would make a racket as it exceeds the sound "barrier" at ground level.

(th)

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#16 2020-03-03 09:29:54

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

South Texas is definitely a candidate launch site, but so are several other places around the country.  If they wanted a site in California or Florida, for example, more launch sites is better, IMO.  One of my over-arching goals for this project is assuring America's access to space by maintaining a mix of critical space flight capabilities.  If such capabilities are lost, reason unimportant, we'll inevitably pay dearly to recapture them.  Flying the Space Shuttle as long as we did was ultimately a mistake, but losing the institutional knowledge and infrastructure for crewed space flight was a far greater mistake.  Hopefully, SpaceX and/or Boeing can help America recapture that critical capability this year.  I don't like the idea of paying the Russians for something we know or should know how to do for ourselves, though I do value our international partnerships where they help us achieve our space exploration goals.

Here's how I view our space technology tools:

StratoLaunch / Virgin Galactic Spaceship / RocketLabs Electron - Assured access to space for quick deployment of military satellites to any orbit at any time, air launch R&D work for airborne aircraft carriers and hypersonic propulsion, and suborbital or orbital tourism

ULA Atlas V & Vulcan / SpaceX Falcon 9 & Falcon 9 Heavy - Dependable workhorses for science missions and exploration class crew transfers

SpaceX Starship Super Heavy / Boeing SLS / Blue Origin New Glenn  - Super heavy lift exploration class vehicles for crewed exploration missions to the inner solar system, perhaps also colonization after we successfully demonstrate the required technologies

Boom Supersonic Business Jet / BAE Skylon & SABRE - Potentially economical supersonic or hypersonic civil aviation for intercontinental travel and pilot training for supersonic or hypersonic airliners

Electromagnetic Catapult Assisted Launch - Economical delivery of consumables, propellants, and raw materials to construct true interplanetary ships in orbit (maybe we could call this company "Wildcat Launch Systems", though it's just an idea and I haven't thought about forming a company all that much; our normal assortment of anti-humanists will be out in force to stop any human progress and the nay-sayers will do their best impression of horses, but I think the idea has merit on account of the enormous flight hardware and fuel cost savings achievable)

In short, we need to expand our mix of capabilities.  Electromagnetic launch is just another capability to add to our space launch technology portfolio.  It's not a higher priority than other capabilities, but I think on-orbit construction is required to send thousands of people tens of millions of miles across space with high confidence in their survivability both in deep space and at their target destination.

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#17 2020-03-03 09:53:39

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 ...

Thanks for adding to the possibility of considering Texas as a location for an electromagnet launch facility.  Of all the locations you listed, Texas is the ONLY location with the kinds of people who might tolerate the kind of intrusion on normal, quiet rural life you are proposing might exist, and THEY are armed (in large measure) and THEY will protect their rights to peace and quiet more vigorously than would a Californian.

It seems possible to me that you (YOU) might be able to convince your fellow Texans to trade the economic benefits of your proposal for the considerable inconvenience and downright distress that will come with it.

The place to start is with the Governor's office.  It will take political leadership at that level to get your proposal to first base with the legislature, let alone with the land owners who would be impacted by the proposal directly, as well as the population at large who would endure the sonic booms.

As you have pointed out on numerous occasions and in numerous topics, the physics and even the engineering have been solved numerous times and in numerous places.  The social aspect of the proposal is what remains to be solved, and of all places in the United States, Texas is the ** only ** state where it could happen at all.

I am allocating time in the near future to go back over your earlier posts to look for elements that might represent opportunities for members of this forum to help. Help from the forum will (of course) consist mainly of sage advice (when available), but it could include outreach if that would require investment of time and a little bit of thought.  It is the outreach that would have any chance at all of moving this proposal from conception to consideration.

(th)

Last edited by tahanson43206 (2020-03-03 09:54:39)

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#18 2020-03-03 10:14:59

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

I have numerous jets fly over my house every day, but I'd rather have the tourists and business men and women those jets bring any day over a slightly quieter lifestyle.  As someone involved in aviation, I can't ask for the benefits on one hand and then complain about the noise on the other.  Aircraft require raw power to move, plain and simple, and making that much power tends to generate quite a racket.  I'm not quite as pessimistic as you are about where we might set up such a launch facility, but I would just pass over any communities that don't want the better jobs, civil infrastructure, and residents with much improved IQ's and paychecks over the average American.  That said, I fully realize we'll have to drag many people kicking and screaming into the 21st century.  So be it.

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#19 2020-03-03 12:53:15

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re topic

Noting #18 ..

I was curious about your concept of a launch to orbit along a chord from the surface of the Earth to a point above the bulk of the atmosphere.

There are lots of calculator web sites.  The one I used today is:

https://planetcalc.com/
756 calculators in total.

Given the mean radius of the Earth at the equator (3963 miles)
Given the approximate height of the bulk of the atmosphere (20 miles)
I selected the online calculator for area of the sector defined by height of 20 on radius of 3963
The chord came out as 795 miles, and half that would be 398 miles.

From this source: https://www.britannica.com/place/Gulf-of-Mexico

We have:

The gulf’s greatest east-west and north-south extents are approximately 1,100 and 800 miles (1,800 and 1,300 km), respectively, and it covers an area of some 600,000 square miles (1,550,000 square km).

Thus, your idea of a flat launch seems feasible, assuming the drag exerted by the atmosphere is insufficient to cause the planned trajectory to fail.

To my surprise, a path only 400 miles long would put the vehicle above the greater part of the atmosphere.

The greater part of the flight path would be over open water and sonic boom effects would become less severe over that 400 miles

Verification of the results are expected and invited, and any corrections needed will be applied as soon as they are received.

Sonic boom effects would be MOST severe at the launch point, where air is most dense, and velocity would be greatest.

To give potential legislative supporters and potential neighbors a sense of what could be expected, a large aircraft capable of multiple mach numbers could be flown over the proposed launch site (with appropriate permissions of course).  The aircraft could even fly the trajectory you've proposed, so that the reach of the sonic boom could be evaluated around the entire Gulf region. 

(th)

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#20 2020-03-04 09:27:01

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For kbd512 re topicl, with focus on the microwave component

Having satisfied myself that your (to me surprising) suggestion of launching to LEO along a 400 mile trajectory is feasible (practical is for others to evaluate), I'm now focusing on the microwave part of your vision.

We have a chicken-egg problem to deal with.  The best possible source of microwave energy for a moving vehicle is a satellite in GEO.  Such a satellite could direct the energy beam to the receptive surface features on the top of the wing and fuselage of a vehicle designed and constructed to take advantage of the power efficiently.

We don't have such a satellite, and the costs of sending the necessary materials to GEO are currently too high for anyone to consider making the investment.

An electromagetically assisted launcher such as you have imagined could supply parts for an SPS much more economically than is possible with any existing technology, and it may even be competitive with Elon's concept if he could achieve total reusability.

In order to take advantage of microwaves from above, it would seem (to me at least) advantageous to design the flight vehicle with a large surface area of air foil, to contain the radio antenna needed to collect the microwaves, and under such a large wing there would be room for the electronics needed to convert the microwaves into whatever intermediate forms are needed to accelerate throw mass to continue driving the vehicle into LEO.

Such a large flat airfoil could be (and most likely would be) quite thin, to reduce as much as possible the cross section of the vehicle as it confronts the dense atmosphere in the lowest 20 miles of the climb.

There is an opportunity for someone with knowledge, experience and whatever else is needed to evaluate this proposal by kbd512.  I can't see any show stoppers other than social ones, but others may well see problems or challenges I'm not aware of.

The US Navy energy storage system kbd512 described sounds scalable to me.  There presently is a surplus of natural Gas in Texas, so that gas suppliers are having to pay to have the output shipped.  That is admittedly a temporary situation, but it does show that there would be a supply of natural gas to charge the rotating mass energy storage systems for a large scale launcher.

(th)

Last edited by tahanson43206 (2020-03-04 09:27:28)

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#21 2020-03-04 12:05:51

Calliban
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Re: electromagnetic launch with microwave propulsion

tahanson43206 wrote:

We have a chicken-egg problem to deal with.  The best possible source of microwave energy for a moving vehicle is a satellite in GEO.  Such a satellite could direct the energy beam to the receptive surface features on the top of the wing and fuselage of a vehicle designed and constructed to take advantage of the power efficiently.

(th)

A large number of geographically dispersed ground based microwave emitters might be a better option.  From GEO at 36,000km attenuation would be significant.  From a few hundred miles away it should be less of an issue.  A ground based emitter can be powered by the grid or a standalone gas turbine and mass is far less important.  You also need to think about single point failure.  If a microwave transmitter goes down for any reason, you would want enough redundancy to allow the vehicle to make it to orbit.

Here is a crazy thought: If we can propel a vehicle electromagnetically to a height of 200km, say, could we unleash an inflatable solar array and use solar electric to power some sort of scaled up arc jet?  Louis has spoken a lot about ultra thin film PV.  Without protective covering, space UV would rapidly degrade the cells.  But they would presumably only need to work for a matter of minutes to boost the vehicle to orbital velocity.

We would need some serious power to do this of course.  So a huge area of cells.

Last edited by Calliban (2020-03-04 12:12:21)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#22 2020-03-04 13:48:39

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For Calliban re #21

Thanks for your quite valid points about how much more effective microwave transmitters would be if they were BELOW the flight path of a vehicle launched from the coast of Texas over the Gulf of Mexico. 

The issue at hand is social, not technical.

kbd512 will have his hands full securing agreement of all the parties that would need to approve a proposal on the scale of this one, just for the launcher which would be installed on dry land.

My best guess is that the first iteration of his idea would involve ALL chemical second stage propulsion.  The microwave idea is certainly technically valid, but the social transformation seems (to me at least) beyond even the remarkable persuasive powers of kbd512.

If the launcher comes into being, and survives as a going commercial operation for a period of time sufficient to ease fears of investors, then addition of microwave transmission facilities on floating power stations offshore might look increasingly attractive.

If you're going for gold here, you can design the microwave pumping stations as floating nuclear reactors which do not depend upon the vagaries of gas supply from onshore, or fickle wind or solar power.

Meanwhile, I'm hoping kbd512 will develop the onshore launching track idea more fully, to the point it can be offered to the primary customers, whoever they may turn out to be.

(th)

Last edited by tahanson43206 (2020-03-04 13:49:37)

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#23 2020-03-04 17:22:39

SpaceNut
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Re: electromagnetic launch with microwave propulsion

I pulled up a map that had a scale on it for Texas to see whether there is open path for travel for a distance of 400 miles.
http://www.washingtonstatesearch.com/Un … s_map.html

This one shows the road which seem quite problematic for open area to build.
https://geology.com/cities-map/texas.shtml

That said runway ramp length would need to rise above the terrain conditions to allow winged launching like a pegasus rocket system would require.

https://infogalactic.com/info/Air_launch_to_orbit

https://phys.org/news/2012-03-maglev-tr … orbit.html

Maglev track could launch spacecraft into orbit proposal is to use scramjet engines after launching from a 2 mi long megLev track launch at around 600mph about what we see for air launch around 30,000 to 35,000 feet..

Pegasus launch profile

Upon reaching a predetermined staging time, location, and velocity vector the aircraft releases the Pegasus. After five seconds of free-fall, the first stage ignites and the vehicle pitches up.

40,000 feet (12,000 m) is only about 4% of a low earth orbital altitude, and the subsonic aircraft reaches only about 3% of orbital velocity, yet by delivering the launch vehicle to this speed and altitude, the reusable aircraft replaces a costly first-stage booster.

The 45-degree delta wing (of carbon composite construction and double-wedge airfoil) aids pitch-up and provides some lift. The tail fins provide steering for first-stage flight, as the Orion 50S motor does not have a thrust-vectoring nozzle.

Approximately 1 minute and 17 seconds later, the Orion 50S motor burns out. The vehicle is at over 200,000 feet (61 km) in altitude and hypersonic speed. The first stage falls away, taking the wing and tail surfaces, and the

second stage ignites. The Orion 50 burns for approximately 1 minute and 18 seconds. Attitude control is by thrust vectoring the Orion 50 motor around two axes, pitch and yaw; roll control is provided by nitrogen thrusters on the third stage.

480919main_ELHVrailtest226x.jpg


https://www.scientificamerican.com/arti … ace-plane/

conventional jets become impractical at velocities exceeding about Mach 2.7 (2.7 times the speed of sound); the inflowing air slows rapidly on entering the engine and generates more heat than most available materials can withstand.

Bond conceived the idea of using the ultracold liquid hydrogen fuel as a heat sink to take the excess heat out of the incoming air and use some of the hot air to support fuel combustion. At the fringes of space, the dual-mode power plant would switch to a conventional rocket engine, drawing on the liquid hydrogen and a small supply of liquid oxygen to propel the winged craft into orbit at a final speed of Mach 25.

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#24 2020-03-04 18:31:22

tahanson43206
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Re: electromagnetic launch with microwave propulsion

For SpaceNut re #23

First, thank you for supporting this interesting topic!

Second, to clarify something ... the 400 miles would be over the Gulf of Mexico.  kbd512's proposed length for the track would be MUCH shorter, and would need to extended only a short distance into the countryside next to the Gulf.

Landing is not part of the initial proposal (as I understand it).  The idea (again as I understand it) is to substitute electromagnetic launch for all or a large part of the first stage boost delivered by traditional chemical rockets.

What is novel and definitely interesting about kbd512's proposal is the idea of launching on a trajectory that is a tangent to the surface of the Earth.  This is a significant change from earlier visions of electromagnetic launch, and while (as with everything) there are trades on the down side, there are significant trades on the up side.

Hopefully kbd512 will be back shortly to explain his vision in greater detail.

Again, launch is over the Gulf of Mexico (a) and (b) it is a flat trajectory by design, to avoid creating excess stress on the wings of the vehicle.

(th)

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#25 2020-03-05 00:40:39

kbd512
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Re: electromagnetic launch with microwave propulsion

tahanson43206,

We don't need 400 miles of track to accelerate the vehicle to booster burnout velocity, nor anything close to that.  The vehicle is going to be accelerated up a launch ramp at a relatively shallow angle for some number of kilometers until it reaches somewhere between Mach 6 and Mach 8.  As soon as the vehicle leaves the launch rail, it's going to pitch up to gain altitude to reduce atmospheric drag, trading some velocity for altitude in the process, and ascend to orbit using its own onboard rocket engine.

Let's consider the case of the SpaceX Falcon 9 Block V to see where our vehicle mass and therefore cost savings may be found:

Total vehicle wet mass with max payload mass: 587t
First stage wet mass: 446t
First stage propellant mass: 418t
First stage empty mass: 27t
Second stage wet mass: 116t
Second stage propellant mass: 111.5t
Second stage empty mass: 4.5t

Max payload mass (to LEO): 22.8t
Max payload mass (to LEO) with booster recovery: 15.6t

So...  If we build a vehicle with a 5t payload, slightly higher initial velocity (substituting for booster burnout velocity) and similar structural mass fraction, we're looking at a 45t vehicle (roughly equivalent to launching an A-3D Skywarrior, a rather large naval aircraft from) to deliver a 5t payload.  Falcon 9 Block V is 25.75 pounds of total mass for each pound of mass delivered to LEO.  Our electromagnetically catapulted vehicle is about 9 pounds of total mass for each pound of mass delivered to LEO, which includes 4.09 pounds of propellant, assuming we just stick with LOX/RP-1.  That's about 2.86 times less mass for the same amount of payload mass.

To launch an equivalent tonnage of payload to LEO as Falcon 9 Block V, we're looking at burning around 205t of propellant a Merlin engine, or slightly less than half of the propellant mass of Falcon's booster or twice the propellant load of the upper stage.  Starship Super Heavy would need 9.9 million pounds of propellant to deliver 100t of payload to orbit.  That's 45 pounds of propellant per pound of payload delivered to LEO.  Our little rocket planes would need 1.98 million pounds of propellant to accomplish the same task using the same Merlin engines.

Put another way, if we allow both systems burn the same total amount of gas, the electromagnetically assisted system can deliver 500t (500,000kg) of payload vs 100t (100,000kg) of payload.  I do not care at all how cheap the gas is when that kind of efficiency is obtainable by supplying some of the power using electrons.

So, why are we bothering with this project?:

Let's say we launch a Starship into orbit, but then we want to refill its propellant tanks so it can actually go somewhere else and do something useful.  We'd need to burn an additional 49.5 million pounds of propellants using Starship tankers to fill it up in LEO.  My system can fill up 5 Starships for an equivalent fuel burn.  Why only send 1 Starship somewhere when you can send 5 of them for the same price?

Alternatively, we launch our Starship empty so it has extra gas left when it achieves orbit that it can then use for orbital maneuvering or reentry and landing if it needs to abort, and then we use our little birds to fill up the propellant tanks, water tanks, supply the consumables, and finally, deliver the crew in increments of 10 or so.  If something goes wrong, we haven't lost 100 trained astronauts or colonists and trash canned the entire mission in the process.  Since we have so many little birds flying around, we can also effect rescues of stranded vehicles or satellites.

Maybe we don't want to deliver straight LOX/LCH4 to orbit.  Maybe we want to deliver H2O and LCO2 and make the propellant in orbit using solar power, just before we leave.  Since there's no cryogenic explosives boiling off by the hour, we can afford to store water and carbon dioxide for quite some time and then convert them for use whenever we're ready.  Let's say we deliver our shiny new Starship to orbit, only to discover that one of the engines has a messed up component.  I guess we should just abort the mission, right?  Are you nuts?  It cost a fortune to get that thing up there and launch opportunities only come around every 2 years.  Send another little bird with a repair crew and replacement parts.

Now let's assume that we're serious about putting 1,000,000 people on Mars.  We're either building 1,000 ships and sending them over 20 years or we're going to build something far larger than Starship or even ITS.  If we build 10 true interplanetary transport ships that can ferry 10,000 people per ship, then we need to make 10 deliveries over 20 years.  That seems a lot less problematic than building / launching / refueling that many Starships and we can support space tourism and business travelers coming and going.  I also want to establish a cloud city on Venus, lunar mines, and asteroid mining.  We need a network of places to travel to in the inner solar system and a way to get out as far as Jupiter.  At present, I don't see much value in going past Jupiter, but Jupiter has Hydrogen coming out the wazoo and if we can figure out a way to obtain and store bulk metallic Hydrogen, that's a very good reason to go there (enabling conventional chemical rockets to obtain a specific impulse of around 1,700 seconds or so).

Anyway, those are just a few of the concepts we'd enable by drastically reducing the consumption and therefore cost associated with space flight.

Edit:
Burning 1.98 million pounds of propellant to deliver 100t to orbit is almost exactly like using the propellant mass associated with a single SLS solid rocket booster to deliver 100t of payload to orbit.  That's absolutely stellar performance compared to what we're using today.

Last edited by kbd512 (2020-03-05 00:44:48)

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