Author Topic: The case for rocket sled assisted launch on a mountain slope  (Read 131505 times)

Offline JohnFornaro

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... for example imagine that such guyed 2.8km high space tube in such special Triple mountain canyon could be build and it could replace 2 solid rocket boosters from Ariane 5 rocket...

Perhaps you could look into the price of that tall building they're constructing in Dubai as a starting point of comparing construction costs.  Your space tube would probably cost more than this building, even if the tube were hollow, because of the dead loads and live loads that it must bear.

You have chosen the wrong verb: "imagine", thus there can be no "proof" in your following arguments.  You could "imagine" that your system could replace 2 Ariane SRB's, and you could "imagine" a number of other things as well.
Sometimes I just flat out don't get it.

Offline Carreidas 160

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Personaly, I always like Burt's 8 GE90-115 engine sled that would release a 400 ton payload at 50,000'.

Now that I'd like to see... Do you have any source for that? Google turns up dry...

Offline Nomadd

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Personaly, I always like Burt's 8 GE90-115 engine sled that would release a 400 ton payload at 50,000'.

Now that I'd like to see... Do you have any source for that? Google turns up dry...

 Just a back of a cocktail napkin. He was speculating on how he might get to orbit back when SS1 was being built.
Those who danced were thought to be quite insane by those who couldn't hear the music.

Offline fatjohn1408

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I try to say that such launch assist system could be worth to explore deeper by higher number of experts, instead of saying that's too expensive, it won't work, but how do you know that ? there are no such design analysis if it exist put link to paper I will happy read and will drop that Idea.

Its non viability is the reason "experts" aren't looking at it.

It is not our job to show it doesn't work, the onus is on you to prove that it does work.

Working around launch systems is a reason that one might know that this wouldn't work

Experts have been looking at it, from Eugene Sanger with the silbervogel in the late 30's over Philip bono with Hyperion in the 60's and Maglifter in the 90's to eLaunch Hypersonics the last years at Nasa. Not to mention some design studies arround ARTS and Hopper in FESTIP.

The thing is governments don't have the guts to follow some out of the box thinking.

From some official simulations that I was fortunate to look into I've seen that at datapoints below 6km altitude, current launch vehicles do not or hardly even reach supersonic speeds and have already burned about 25 percent of their fuel. This due to the fact that more than half of their generated Delta-V goes into losses rather than flightpath speed.

So although its tempting to think about some more extreme concepts, even fairly low performance launch assists can decrease the dimensions of launch vehicles significantly or alternatively increase their payloads.

In addition I think that rocket sled propulsion would work better for this porpuse than for instance maglev propulsion or a mechanical catapult working with dyneema cables and pulleys (although I was really amazed by some napkin calculations, might be a real possibility when thinking about lunar mass drivers (free breaking length effectively multiplies with a factor of 6 due to low gravity, but that is another discussion)

The problem also might be that previous studies mentioned were only done by 'rocket scientists' and not in cooperation of civil engineers, at least the major attention mostly goes to the launch vehicles that are designed to utilise the launch assist.


Offline Jim

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Experts have been looking at it, from Eugene Sanger with the silbervogel in the late 30's over Philip bono with Hyperion in the 60's and Maglifter in the 90's to eLaunch Hypersonics the last years at Nasa. Not to mention some design studies arround ARTS and Hopper in FESTIP.

The thing is governments don't have the guts to follow some out of the box thinking.

From some official simulations that I was fortunate to look into I've seen that at datapoints below 6km altitude, current launch vehicles do not or hardly even reach supersonic speeds and have already burned about 25 percent of their fuel. This due to the fact that more than half of their generated Delta-V goes into losses rather than flightpath speed.

So although its tempting to think about some more extreme concepts, even fairly low performance launch assists can decrease the dimensions of launch vehicles significantly or alternatively increase their payloads.

In addition I think that rocket sled propulsion would work better for this porpuse than for instance maglev propulsion or a mechanical catapult working with dyneema cables and pulleys (although I was really amazed by some napkin calculations, might be a real possibility when thinking about lunar mass drivers (free breaking length effectively multiplies with a factor of 6 due to low gravity, but that is another discussion)

The problem also might be that previous studies mentioned were only done by 'rocket scientists' and not in cooperation of civil engineers, at least the major attention mostly goes to the launch vehicles that are designed to utilise the launch assist.


Those "experts" never bent metal.  Paper studies, like what you are posting, always work on paper. 

It has nothing to do with governments.   If it were that much of a benefit, then a commercial entity would door.

It has nothing to do with consulting civil engineer either.

Plain and simple, the concepts don't provide enough of benefit to be worth the effort, plus they are constrained.
« Last Edit: 05/03/2011 09:44 pm by Jim »

Offline QuantumG

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Human spaceflight is basically just LARPing now.

Offline fatjohn1408

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http://moonandback.com/2011/04/08/jesse-powell-in-a-t-minus-5-on-ultra-low-cost-launches/

http://www.startram.com/

$20B to start, good luck with that.



Yeah I knew about that one. I also think this one is far out there.
But even though on the surface it might look that the performance benefits are minor compared to constraint and cost disadvantages.
But, there is always a but, if this relatively small performance upgrade tears open the realm of reusable single stage to orbit systems then it is worth a shot. Because no matter how you twist and turn full rocket SSTO is and will never be a viable concept.

Offline Epis

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you cant ignore Laws of physics, and laws of nature that says that in the end most energy efficient way of doing things will survive fare competition in market. look at cars, computers, its all about energy efficiency cheapest staff is staff that was manufactured with less energy. and in rocket world it will be the same, its only mater of time. there is rocket engine propulsion energy efficiency chart:
http://upload.wikimedia.org/wikipedia/commons/5/5f/PropulsiveEfficiency.svg

what do you see in that chart ??
its equation were speed is divided by exhaust velocity so when rocket lights its 1 stage engine its total efficiency is 0 %   ???
and I am thinking isn't that insane ? building rocket whose starting efficiency is 0%.
its no no-brainer to see why it needs so much propellant to move its weight off the ground, because its total waste of energy.
now compare that rocket 1 stage Total energy wasting cycle with launch assist, like Maglev, and cannon style tunnel launch all those are Max energy efficient at first micro Second of operation >50% total efficiency.
This is the answer why my primitive tower launch calculations show >10x energy efficiency, for each kg of payload put in LEO, because rocket engines are high efficiency engines only at high speeds thousands of Km/h but at low speeds its total waste of power, so I replace its power wasting 1 stage LEO cycle with high efficiency tube launch assist and got 10X immediate improvement in cost per payload because rocket cost in $ is actually real energy value that is needed to make that rocket, including fuel, fuel is just a fraction of energy that needs to build rocket, so it all summs up to Total rocket cost, and if second rocket stage is 1/3-1/4 of total cost then it is 3-4 times energy efficient by nature and delivers >3x payload to LEO by its payload/weight ration so total is ~10x energy efficiency gain based on all rocket cost estimation. and rocket cost is real energy efficiency estimation number, because as i sayd fuel it self is just a small portion of rocket cost, so does energy required to make all rocket and by removing first rocket most inefficient stage we will have huge energy savings.

Launch infrastructure will be just few % of total launch cost, it is like Airplanes where you buy one for enormous price and ticket price don't cost you miljon $$ instead largest cost % is for fuel which could be seen as energy, so one you build launch high efficiency 50%+ launch assist system it will pay for itself and will be always more than 10x cheaper than conventional rocket, no mater how cheap they will get, how fart advance 10x will stay because same technology will follow launch assist rockets but they will be >10x more energy efficient so 10x cheaper no mater what.

based on this simple energy efficiency assumption first stage NTR engine would be 3x more waste energy than SRBs stage and 30x more energy waste than Launch assist, but if using NTR engines for second rocket stage it would be OK like LH2/LOX engines, because at that altitude and speed its energy efficient way of LEO rocket launch Cycle.
« Last Edit: 05/04/2011 09:24 am by Epis »

Offline Epis

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IF I was Usa president obama knowing this 1 stage rocket energy efficiency I would issue statement of cancellation all rocket programs and finances  to systems which energy efficiency in first 10 seconds of operation is below 10% Total efficiency, and direct money to new systems that's energy efficiency are higher than 30% in first second of operation till 1 minute of operation, and launch assist systems must be built for 1000+ launches opening new age of high efficient space tech LEO launch systems.

Offline Jim

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Yeah I knew about that one. I also think this one is far out there.
But even though on the surface it might look that the performance benefits are minor compared to constraint and cost disadvantages.
But, there is always a but, if this relatively small performance upgrade tears open the realm of reusable single stage to orbit systems then it is worth a shot.

No, there is no "buts".  The constraints make it unusable.

Offline Jim

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IF I was Usa president obama knowing this 1 stage rocket energy efficiency

The efficiency doesn't exist.  There is no place in the USA for such a system.


Offline Jim

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you cant ignore Laws of physics, and laws of nature that says that in the end most energy efficient way of doing things will survive fare competition in market.

wrong, it is the cheapest.  Also, you still haven't proven that this will work.  You are ignoring engineering
« Last Edit: 05/04/2011 12:38 pm by Jim »

Offline fatjohn1408

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Yeah I knew about that one. I also think this one is far out there.
But even though on the surface it might look that the performance benefits are minor compared to constraint and cost disadvantages.
But, there is always a but, if this relatively small performance upgrade tears open the realm of reusable single stage to orbit systems then it is worth a shot.

No, there is no "buts".  The constraints make it unusable.

Unusable? Its not like you only have one specific orbit that you can target. The majority of delta-V should still be provided by the launch vehicle which can be done in any direction one wants. With the use of lifting surfaces the orbit inclination can even be shifted significantly without serious losses (providing a good L/D) after leaving the rail.

Granted that the advantage of a rail parallel to the equator won't provide much advantage for missions to polar orbits.

But that is not where most payloads go. Unusable? I don't think so.

Offline Jim

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1.  Unusable? Its not like you only have one specific orbit that you can target. The majority of delta-V should still be provided by the launch vehicle which can be done in any direction one wants.

2.With the use of lifting surfaces the orbit inclination can even be shifted significantly without serious losses (providing a good L/D) after leaving the rail.

Granted that the advantage of a rail parallel to the equator won't provide much advantage for missions to polar orbits.

3.  But that is not where most payloads go. Unusable? I don't think so.


1.  The turn to the proper azimuth will incur losses

2. enough to negate the savings

3.  most payloads don't go to equatorial either, hence "unusable" because it doesn't provide savings since other sites are required.
« Last Edit: 05/04/2011 12:33 pm by Jim »

Offline fatjohn1408

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1.  The turn to the proper azimuth will incur losses

2. enough to negate the savings

3.  most payloads don't go to equatorial either, hence "unusable" because it doesn't provide savings since other sites are required.

1. For a large range of azimuths it won't be enough losses to negate savings

2. Not true for all azimuths, gains are provided of lift effectively transfering the vehicles momentum in the right direction. The losses are drag. Drag is easily smaller then lift.

3. If that is true, why does everyone bother with launching from the equator? Launching with an assist is just like launching with a higher earth rotational velocity, which is widely believed to be an advantage for the majority of launches, except the few to polar orbits.
« Last Edit: 05/04/2011 01:34 pm by fatjohn1408 »

Offline Jim

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1. For a large range of azimuths it won't be enough losses to negate savings

2. Not true for all azimuths, gains are provided of lift effectively transfering the vehicles momentum in the right direction. The losses are drag. Drag is easily smaller then lift.

3. If that is true, why does everyone bother with launching from the equator? Launching with an assist is just like launching with a higher earth rotational velocity, which is widely believed to be an advantage for the majority of launches, except the few to polar orbits.

1.  You don't know that.  Dog legs do reduce payload capability.

2.  No, there is drag due to lift and the weight of the aerosurfaces.

3.  It is true.  Since 2009, 17 of 21 US launches were non-equatorial.

Also, nobody launches from the equator, not even ESA.

Launch "with an assist"  has not been proven engineering wise and economics wise.  It is all paper exercise and nothing more.  It can't be translated into reality.  Additionally, there are no locals in the US that can serve this idea.



Offline D_Dom

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Also, nobody launches from the equator, not even ESA.

Not trying to defend this launch assist theory but commercial launch services are sending payloads to orbit from the equator.
http://forum.nasaspaceflight.com/index.php?topic=8862.msg723894#new
« Last Edit: 05/04/2011 03:23 pm by cygnusX1 »
Space is not merely a matter of life or death, it is considerably more important than that!

Offline Jim

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Also, nobody launches from the equator, not even ESA.



Not trying to defend this launch assist theory but commercial launch services are placing payloads to orbit from the equator.
http://forum.nasaspaceflight.com/index.php?topic=8862.msg723894#new

you got me on that one. I forgot.

Offline Epis

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if tall space towers are too since-fiction for you then lets go to traditional mountain side Maglev in vacuum tube 5-6km long,  or cannon style 5-6km tube attached to mountain side. these system have well known technology. Price of building isn't low (couple of billions $) but main problem as I understand are mountain availability so here are few examples of Most extreme mountains that could be used in theory for mountain slope rocket launch assist.
first is Peru volcano mountain (this is my favorite) it has very long mountain slope 6km long and elevation is also quite good 2.9km Top altitude is 5780m so its very good height with favorable atmosphere pressure and density for very high Mach speed rocket exit.  as you can see mountain has +- straight slope it would need little digging and it won't cost much to smooth it and then straight launch tube could be placed.
using such mountain slope rockets could be accelerated with 15G and exit speed could be 4829 km/h (Mach 4) and rocket could reach altitude 90km so accelerating rocket with 15G for 6km would give rocket same amount of delta V as conventional first rocket stage, so it would be  direct first rocket stage competitor.
bad thing about that mountain is that it is facing south with few tens degrees east. but its not so bad there are 2 options: first it could be possible to dig launch tube deeper in mountain to make larger launch angle then it would be easier to correct flight direction and more orbits could be taken, second way would be build tube on west mountain side, but it is much longer, and lower degree so orbit will be more fixed equatorial, so less flexibility and I don't like such fixed orbit launch track idea.
second picture is Coolest maintain cliff in the world its drop is 3500km deep angle or all drop is about 50 degrees and 5km long launch track could be placed there, top altitude would be incredible 8568m above see level, in theory higher launch speeds could be possible maybe Mach 5-6 exit speeds. disadvantage is its location in pakistan, and hard to reach place with no infrastructure + at the bottom there is glacier so no hard surface to construct any launch platforms.
in the USA there are no such super high mountain slopes, I think that's main reason for that type of Idea rejections.

Offline Jim

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15g is too much,

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