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This topic is offered for those who may wish to develop the concept as an alternative to vertical launch assistance.
The topic is inspired by a proposal by Calliban, in the Vertical Launch Assist topic:
I think it is sensible to redefine the concept as 'launch assist' rather than 'vertical launch assist'. I initially favoured vertical launch, because this is how Starship is designed to launch. But as SSTO is a new concept designed from scratch, there is no need to be constrained by engineering legacy. Additionally, it appears that horizontal launch, or at least launch along an incline, is more optimal from the viewpoint of reducing gravity losses. This seems counter intuitive, until you realise that the Earth surface is curved. Even an entirely horizontal launch, still has a vertical velocity vector w.r.t Earth's gravitational equipotential lines.
It is much cheaper to build a horizontal launch assist and it isn't constrained by topography. It allows for a higher velocity launch assist at more modest acceleration. It is therefore better. To avoid centifugal acceleration, the horizontal launch track will need a slight slope away from Earth surface, because the Earth curves beneath it.
The baseline concept is for a 50m/s2 constant acceleration, providing a 300m/s launch assist. This requires a track length of 900m, or 2925'. The propulsion method is open at this point.
*************************A steam rocket perhaps? Assuming we heat water close to its critical point 372°C and assuming a 30% conversion of heat into kinetic energy, exhaust velocity will be ~1km/s. This is quite a simple device. A steel pressure vessel full of hot water at 370°C. Upon opening a valve, hot water expands into a DeLavelle nozzle, where it flashes to steam. Due to the mass of the steel vessel, this design has a limited final velocity, no more than 0.5km/s. But should be entirely capable of reaching a velocity of 300m/s. As the tank empties, the pressure declines. The temperature declines as part of the energy within the remaining hot water flashes to steam to fill the empty tank space. The valve will need to throttle open as the tank opens to maintain flowrate and thrust.
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Last edited by tahanson43206 (2024-06-04 06:15:02)
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This post is reserved for an index to posts that may be contributed by NewMars members over time.
The topic necessarily requires identification of a location on Earth where the facility is to be built.
In addition, the topic necessarily requires identification of shock wave mitigation measures that will be required if humans are within audible range of the launch.
It should be noted that the forum archive contains posts that consider this question in some detail.
In particular, an initiative by kbd512 explored the feasibility of a purely horizontal launch, with the feature that Calliban has identified... the curvature of the Earth insures that a vehicle launched with sufficient impulse along a tangent to the surface of the Earth will eventually reach LEO and eventually escape velocity.
The energy absorbed by the atmosphere along the path of the proposed vehicle will translate into sound energy.
The vehicle will be designed to tolerate the heating of the exterior that can be expected due to the high rate of travel through the dense lower atmosphere.
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Last edited by tahanson43206 (2024-06-04 06:22:06)
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tahanson43206,
I don't think a pure vertical or horizontal launch will be very practical. My thought about this was that the launcher was going to be some kind of inclined ramp which "soft launches" the vehicle after the engines spool up to full power, which then accelerates the vehicle to 5g (1.5g provided by the engines, 3.5g provided by the catapult), whereupon the vehicle is flung off the ramp with a vertical and horizontal velocity component to it. I don't know what the exact optimum launch angle should be, probably somewhere between 30 and 45 degrees.
This is a fairly aerodynamic lifting body vehicle, relative to a Space Shuttle or any orbital class rocket, so the idea was to get the vehicle moving downrange as fast as possible, as soon as possible, rather than thrusting straight up the way a conventional TSTO does, where most of the booster propellant is translated into altitude gain for reduced aerodynamic drag, but also a pure gravity loss over that entire vertical thrusting period of 2 to 3 minutes. The "vertical thrusting period" associated with a prototypical TSTO accounts for around 1km/s of the average 1.5km/s total gravity losses, which is significant for a TSTO but huge for a SSTO. A TSTO's booster causes it to pick up quite a bit of velocity, yes, but not perpendicular to the surface of the Earth, which is what you require to stay in orbit. That's why you don't see TSTO vehicles move very far downrange during the boost phase of ascent, which is why high Isp in the upper stage is such an enabler- it allows the upper stage to pour on the speed over a greater period of time, out of the sensible atmosphere. This SSTO vehicle will still be ascending quite rapidly, but not a pure vertical ascent like a traditional TSTO. It has a real TPS covering the entire vehicle, and aerodynamic heating won't be nearly as bad as reentry. It has the excess thrust to accelerate very rapidly, so it takes about half as long to ascend to orbit as a traditional TSTO like the Space Shuttle.
Space Shuttle ascent to orbit is nominally a 520s flight duration. There's some room for them to tweak ascent profile, but not much, because it doesn't have the thrust. My SSTO will achieve orbital velocity (not "be in a circularized orbit", obviously), after less than 250s of flight time. That makes very different flight profiles "more optimal" for my SSTO.
That small 300m/s initial starting velocity is enough of a boost to either significantly reduce propellant volume or increase payload. Since our composite airframe structures, engine thrust-to-weight and reliability, as well as TPS are all "on point" for this application, my preference is to reduce the propellant load by about 150t. If it turns out that we get an even greater reduction in gravity losses that are not offset by corresponding aerodynamic drag, then we further reduce the propellant load. This has the effect of making the vehicle meaningfully smaller, less costly, more aerodynamic, etc. It's a virtuous circle.
As to your idea behind using a nuclear reactor, I don't think we need a reactor at all, nor would adding one be particularly helpful.
Let's consider what EMALS does:
135kWh of electricity accelerates a 45,000kg aircraft to 240km/hr in 2 to 3 seconds.
Let's translate that for our purposes:
We want 1,080km/hr (300m/s), 4.5X that of USS Ford's EMALS output.
607.5kWh to launch a 45t aircraft at 1,080km/hr.
300m/s directly translates to 150t less propellant, so let's assume a 1,950t launch weight.
(1,950t / 45t) * 607.5kWh = 26,325kWh or 26.325MWh.
These figures are what the launcher would require to provide 100% of the launch acceleration force, so it's an upper limit as to what would be required. In reality, the engines aboard the launch vehicle are supplying approximately 30% of the total launch energy.
Let's be realistic about launch rate. Say we want to launch twice per day from a single launch rail. This involves propellant loading, passenger loading, last-minute vehicle checks, inspection of all launch equipment, etc. That means our daily power consumption is 52,650kWh.
EMALS stores energy in flywheels. If we charge those flywheels over a period of 4 hours, then our average power delivery rate is 6,581.25kWh per hour, for 4 hours. You don't need a nuclear reactor to supply that kind of power. You just don't. If you did include a reactor, it would be a micro-reactor, it would charge the flywheels up inside of 1 hour, and then you're waiting for propellant loading to complete for 2 to 3 additional hours. What are you doing with that very expensive reactor asset the rest of the time (because it has to be monitored 24/7)? That makes very little sense to me. You can charge up the flywheels while you're doing everything else, so then you don't have employees milling around while waiting for other tasks to be completed.
A pair of 3.5MWe natural gas powered Caterpillar G3616 diesel-electric generator can supply that kind of power for around $5M in total cost, while burning 8,555.625kg (195,594.75ft^3; $2,423.42 using avg Texas prices) of natural gas. These electric generator engines are suitable for the kinds of applications which we intend to use them for, they're actually used for industrial electric power generation, and available for relatively low cost compared to any nuclear reactor.
Those brand new / never installed government surplus engines are being sold for $1.8M each. Newer versions of that same engine, with more recent upgrades for emissions and fuel economy, are available for a minor additional cost. These engines are incredibly common for pumping natural gas or supplying backup electrical power to hospitals and such, highly reliable (more run time between overhauls than the LM2500, on average), and widely available for reasonable cost.
LOX loading is at least 2 hours to account for gradual cool-down of the composite tank, followed by 1 hour of fuel loading. I expect careful / methodical passenger loading to take 1 hour. That's at least 4 hours of launch prep time per launch. There might be ways to speed that process up, but none of them are particularly advisable courses of action. LOX, RP1, passengers, in that order. That's been proven to work.
For a single 8 hour work day or morning shift, we can realistically execute two launches per shift. The evening shift handles landing and vehicle inspection. The night shift oversees vehicle maintenance and repair. That is a realistic flight schedule for an airline service with 2 launch vehicles. If you want to add flights per day, then you procure 2 additional generators, 2 flywheel storage systems, 2 vehicles, 2 additional propellant storage tanks, and another launch track. If you think you want additional capacity from the outset, then you procure a LM2500+G5 marine and industrial gas turbine electric generators, which deliver up to 40MWe.
If you will only launch twice per day, then the LM2500 is an expensive extravagance, and these gas turbines don't really appreciate being started up and shut down on the daily. Diesels don't care about that nearly as much, which is why diesels make so much more sense for this intermittent power application. Fuel economy between the latest versions of the G3616 and LM2500 are about equal.
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EMALS it is. According to the wiki reference, steam catapults were reliable but had poor energy efficiency. They also subjected the airframe to heavy vibrational loads, which could cause damage. If that is a problem for a fighter jet, it will be an even bigger problem for a structurally slender SSTO. If all we need is 6.6MW, then we can draw power from the grid.
https://en.m.wikipedia.org/wiki/Electro … nch_System
Only 1 problem, not sure how big a problem it is. EMALS is a military system. SSTO launch is a civilian use. Is it possible to procure this for a non-military use?
Last edited by Calliban (2024-06-04 11:19:58)
"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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I think the problem with a sloped launch ramp, is that you must either find a mountain close to where you want to launch or build a very tall sloped platform. If we assume a launch ramp that is 1km long and we take the upward slope to be 30°, the ramp will be 500m off the ground at its end. That is as tall as some of the world's tallest buildings. It could be done, by mounting the ramp on cross-braced concrete pillars. But it will be expensive to build. One of the biggest building projects ever done. A horizontal (or close to) launch ramp is going to be a lot cheaper to build. We can deal with a slight incline using soil berms for the first part of the track with concrete supports as it ascends further from the ground.
I don't really know enough about how to cost civil engineering projects to be able to assess the likely capital cost of different concepts. But a 500m high launch ramp for a 2000te ship, looks like a lot of work to me. This sort of question would ordinarily be answered by cost-benefit analysis.
"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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It is an art to solve problems as now a location that fits the model with alteration.
It means a carrier sled with or without wheels.
Electrified with a tremendous level of power with each use in a short period of time.
It's one of the reasons that they stopped going towards the electrical due to component breakdown.
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For Calliban re #15
You probably have a good reason for the choices you offer your budding entrepreneur.
I can't read your mind, so must deduce there is a reason you've omitted excavation from your concept.
A ramp that is 500 meters deep will have provided the material for a ramp that is 500 meters high.
The Romans built such a ramp a while ago, when they slowly but surely captured Masada.
The material for that ramp had to come from somewhere.
Per Google:
The Romans, commanded by Lucius Silva, laid siege to Masada, building a circumvallation wall around the mountain. A blockade would have been lengthy, however, because the defenders had plentiful food and water supplies. So the Romans also set about building a massive earth ramp on the western side of the fortress.
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Last edited by tahanson43206 (2024-06-04 17:58:05)
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For Calliban re electromagnetic launch....
All the ideas for magnetic launch were discovered and published and (most likely) patented decades ago.
I'd be astonished if the US military (or any military) has any kind of hold on the technology whatsoever.
If you ever have an interest in the early history, look up Henry Kolm of MIT.
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Calliban,
We're going to launch from Cape Canaveral or Vandenberg. Both are US Air Force / US Space Force bases. Use of government furnished equipment from space ports is not a major issue here in America. Uncle Sam owns some of the equipment at every civil airport, for example, even if it's operated by civilian contractors. This is not frequently a major issue for us. Contractors run all of our government arsenals that make munitions, for example. The equipment is owned by the government, but operated by a rotating set of contractors for a number of years before bids are resubmitted. The contractor is allowed to make a modest profit, something small like 2% to 3%- quite a lot of money over the entirety of the contract, to supply or transport arms and munitions for our military. They typically hire veterans who already have expertise and security clearances, so we would hire US Navy veterans who were involved in EMALS operations and maintenance. They have a civilian job to go to after their military service where their expertise is directly and uniquely applicable.
To be perfectly frank, you get a background investigation, security clearance, and data protection methods dictated to you whenever you start designing, building, and operating launch vehicles. Typically, the US Air Force funds your project with seed money, and then you're beholden to the government for national security reasons, in exchange for all the technical assistance (software design tools, NASA technical experts, materials tech databases, etc), test facilities access (engine test stands, launch facilities), development funding, and other perks provided. I suppose someone could do all of this without any government funding, and then their project is not subject to ITAR or national security restrictions, but in actual practice that is always what happens. You could view it as "golden handcuffs", but this is not something I'd ever give to Russia or China, so I don't personally view it as a major imposition on the project, merely the cost of doing business.
The catapult system is dual-use equipment, so ITAR applies, but China already has EMALS. Russia has never had a major ship-based naval aviation institution to my knowledge. Lots of shore-based patrol assets, but mostly helicopters aboard ship. That's congruent with their fighting doctrine. America, China, France, Italy, Japan, and the United Kingdom all operate aircraft carriers, in keeping with their fighting doctrine. Nobody else has the resources to construct a CATOBAR aircraft carrier, except for allied nations. If they do, then they'd negotiate for and outright purchase the equipment from the US Navy's prime contractor, the same way the French purchased their steam catapults. We actually paid some South American military forces to maintain and operate aircraft carriers during the Cold War, which they did, but they couldn't justify the costs and either returned the hardware or purchased land-based jets to avoid the hassle and expenses associated with naval aviation. Aircraft carriers are expensive military assets, as the British are well aware.
You cannot readily take / steal / adapt this launch system to an aircraft carrier, if that's what you're thinking. It's a bespoke solution for which the equipment must be designed and fabricated, but the US Navy / General Atomics EMALS makes it an engineering exercise at this point, rather than a science project, which is what the US Navy started with.
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It looks like dual use isn't going to be a problem. I don't think anyone would want to sell this tech to geopolitical rivals anyway, so this isn't going to be an imposition.
The idea of building part of the launch ramp in a tunnel seems sensible to me. It is likely to be cheaper than elevating the ramp to hundreds of metres above the ground.
This project accords well with the Permanence principle. Once the device is built, we can continue to use it for centuries with proper maintenance. This is one reason to avoid putting the ramp on reinforced concrete legs that explode after 40 years when the weather gets to them. The walls of a tunnel are compressive structures.
The ship will sit on a sled, which transfers load to manganese steel rails, via sliding shoes. Upon releasing the SSTO, the sled will rapidly decelerate. Any thoughts on the best option for doing that?
Building the majority of the ramp underground, allows the SSTO to be lifted by EOT crane onto the sled, which then both slide down the tunnel.
Last edited by Calliban (2024-06-05 15:13:24)
"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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Calliban,
If this launch device was built into the side of a low mountain range on the East or West Coast, then excavating a tunnel is not required. It requires industrial natural gas powered diesel-electric generators commonly used in oilfield or mining operations, some rock quarrying to cut the launch track into the side of the mountain, and EMALS-like technology, none of which are major technical or cost challenges. So long as the blast pit is a gravel or rock pit below the start of the launch track, it requires no water sound suppression system. Taken together, that reduces the major cost elements of this project to EMALS design and construction.
The Most Famous Energy Storage Project In History
Based on the cost of the Stephentown flywheel energy storage facility in New York State, present construction cost should be somewhere between $40M and $50M.
Let's say $50M for this bespoke project to use CFRP flywheels storing about 25kWh of power each, with total capacity around 50MWh, or 211 such devices, very similar to the 200 flywheels installed at Stephenstown for $43M in 2020.
Now we need to guess at what the EMALS track will cost based upon a scale-up of the existing tech used aboard Ford class aircraft carriers.
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We need to do everything we can to contain cost and complexity.
Building a "Bond Villain" lair underground, while super-cool and exciting, is also super-expensive and complex.
Q: Why use inclined ramp catapult-assisted launches to begin with?
A: A 300m/s initial velocity increment reduces propellant mass by 150,000kg. Alternatively, EMALS increases payload or vehicle dry mass allowance by 14,000kg for the same 2,000,000kg propellant load, which allows us to construct a very robust launch vehicle, relative to any existing rocket, regardless of how many stages it has.
Q: Why natural-gas fed G36 series Caterpillar industrial / marine diesel-electric generators?
A: G36 series machines have no issues with the duty cycle being demanded of them, they are low-cost relative to gas turbines, easy to maintain according to their maintainers, pervasively used for providing off-grid industrial power, natural gas is plentiful in the US, and these engines are mass manufactured in the US. No additional grid load is being demanded from our grid, so flight operations are not contingent upon the grid's available capacity. We should still do a trade study on photovoltaics and wind turbines to see which option is actually cheaper. Lowest cost with reasonably good availability wins. If we get a sweetheart deal from a local wind farm, then we take it, because power generation equipment is then one less thing we have to buy and maintain. Intermittency is far less of an issue in this application. If there's a week or three out of the entire year where we can't launch because the grid needs power, then that is not a major problem. Space flight is a voluntary human activity only undertaken in ideal conditions.
Q: Why use LOX as the oxidizer?
A: LOX is the most performant non-toxic oxidizer available, only moderately cryogenic, denser than water, very cheap to procure, and storable for the brief periods of time that we need to store it over. LOX is not inherently dangerous and toxic the way high concentration H2O2 or NTO or other room temperature storable oxidizers are. No other oxidizer has that mix of desirable properties. Composite materials with appropriate resins or propellant tank coatings are proven to be LOX compatible. The other oxidizers are not known to be composites compatible, because there's little to no available test data, let alone long term tests, thus no resins developed to be compatible with them.
Q: Why use RP1 as the fuel?
A: It results in the most compact and lowest dry weight launch vehicle for a given payload, for a SSTO. Engines that use LOX/RP1 produce the most thrust for the lowest weight. Modern engines burn it cleanly, without creating internal soot deposits or external soot plumes that people find objectionable- the aesthetically pleasing "pale blue flame" characteristic of LOX/LH2 and LOX/LCH4 combustion, which indicates complete combustion. On top of that, we can get RP1 in the quantities required, it's simple and easy to handle and store when compared to any cryogen or toxic Hydrazine family fuel, the airline industry knows how to handle JP / RP fuels, and it requires no exotic materials or special techniques to use. Kerosene is compatible with composite materials, as evidenced by all the wet wing jet airliners and military aircraft using composite skins and structural wing or fuselage members also serving as fuel tanks. The incredible thrust provided by RP1 engines means you're in space inside of 2 minutes, rather than 8 minutes using LOX/LH2 and solid rocket boosters. That's about as fast as we can reasonably accelerate without endangering human health.
Q: Why EMALS as the catapult launch technology?
A: EMALS allows for a "soft launch" in a way that most other types of catapults do not, and is a scalable system that is highly efficient at transmitting acceleration force to the aircraft or spacecraft being catapulted. It works acceptably well at the launch rate required, and maintenance is not a problem for a shore-based facility that launches twice per day, relative to an aircraft carrier catapult that might launch a dozen times per hour.
Q: Why use flywheels to power EMALS?
A: EMALS is powered by flywheels aboard aircraft carrier, and flywheels are a good match for the duty cycle and discharge rates demanded of them. Super capacitors would be ideal, but incredibly expensive. Motor-generators and flywheels are simple machines that work well when no weight or size constraints apply.
Q: Why use the side of a mountain on the East or West Coast?
A: It will launch the vehicle with enough speed to clear the coastline and ascend to orbit over the water, which the FAA takes no issue with. Building the tunnel into a channel running up the side of the mountain means no complex water deluge sound suppression system is required, the vehicle or channel doesn't get sprayed with water, thus nothing to corrode the working components of the EMALS. We're launching twice per day from a reasonably remote area, thus the noise won't be overly-objectionable.
Design and operational decisions need to be very shrewd and business-like, with no consideration given to beliefs. Whatever is lowest cost, simplest, and reliable for the intended purpose will take precedence over more ambitious but expensive alternatives unless clearly definable business objectives would be met by developing or using those alternatives.
The overarching business goal is to operate a reliable passenger airline-like service to LEO, for delivery of crews to colonization ships bound for other worlds or various space stations. The entire reason civil business development of space is so scant, is that there simply aren't very many people living and working in space. No people equals limited business opportunity, apart from communications or remote sensing. This venture aims to change that by providing reliable Earth-to-orbit mass transport using aircraft-like vehicles that ascend to orbit using a single engine burn and then landing the way gliders land. It eschews expensive and exotic propellants or propulsion systems, requires minimal infrastructure development, and makes use of the latest composites, thermal protection systems, and efficient staged combustion kerosene-fueled rocket engines, minimizing per-passenger aerospace vehicle mass and propellant burn.
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For all ... it is definitely encouraging to see this topic developing in a robust manner!
The scale of the project is greater than any EMALS design attempted by humans, but on the face of it (at the 30,000 foot level) it does not appear that anything new has to be invented.
The benefit to the region that hosts this system would be economic. No one else is likely to attempt anything on this scale.
The risk for the developer is to overcome fears of the population near the facility. The ideal location for a facility like this is near the equator, but on the other hand, there may be locations inside the US where it would work in a technical sense, and where the population would be willing to support it.
Once set into concrete, this facility will dictate the orbital plane where on-orbit activity will occur
Some thought needs to go into site selection.
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According to this document from Sandia National Labs, the design lifetime throughput of each flywheel energy storage system installed at Stephentown, New York, is 4,375MWh.
20 MW Flywheel Energy Storage Plant
If each flywheel charges and then discharges 25kWh worth of energy, or enough design service life to execute 175,000 launches. At 500 passengers per flight, that equates to launching 87,500,000 people into space. Per passenger cost, if the complete system such as the one at Stephentown, which cost $43M, is $2.03. 52,650Wh worth of electricity is required per launch. At $0.15/kWh, that adds $7.90 to the cost of each ticket. Each passenger is paying for 4,000kg of propellant, which includes 1,471kg of RP1 and 2,529kg of LOX. The LOX is around $1.00/kg for an onsite LOX plant, so $2,529 for the oxidizer. If RP1 is $3/kg, then $4,413 for the fuel. All together, our energy costs are $6,951.93. This is near the upper end of a business class ticket from LAX to Tokyo.
If we consider the cost of our engines, at around $200,000 per engine (based upon costs for SpaceX Raptor), and we need 12 engines of the same thrust class, so that's $2.4M. If the engines are used for 100 flights before being replaced, that adds $48 to the cost of each ticket to purchase the engines.
We need to evaluate the expected airframe and thermal protection system costs and anticipated service life based upon similar Space Shuttle TPS components and service life. The goal is that the airframe lasts for 1,000 missions, TPS for 100 missions prior to complete replacement over those 100 missions, with tile replacement occurring as tiles are damaged or judged unfit for service. LH2 tanks have been tested to and survived 100 pressurization cycles, 3g acceleration loads, compression loads, etc. High pressure CFRP H2 tanks used in fuel cell cars are rated to somewhere between 20,000 and 25,000 pressurization cycles before replacement is required.
GW says we need to take X-rays of the composite airframe / propellant tanks after fabrication, and then more X-rays any time someone drops a tool on the airframe, to assure that there is no fiber damage. Maybe there needs to be a rule that tools for tile repair are attached to a neck lanyard with handles wrapped in foam to avoid unintentional impacts, and repair techs need to wear socks while crawling over the airframe to inspect and repair the TPS, engines, and other systems. If a tool is dropped, invisible damage to the structure can occur, according to the NASA test documentation I have regarding filament-wound composite solid rocket motor casings. This document is applicable to all thin fiber-wrap propellant tank structures such as the airframe we intend to build. On that note, impacts from mating / latching the airframe to the catapult truck used to launch the vehicle cannot be tolerated. We need some sort of carriage system to move the orbiter through the repair facility without beating up the airframe.
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