pulse-ram-scram jet single stage to orbit ?

Nasa is looking for single stage to orbit system which would benefit from an air breathing engine able to use atmospheric air (while available) and save on some of oxygen mass. I think they worked out that latter stage should be a scramjet. My suggestion is to build engine that operates as pulse jet at 0-0.8M, ramjet up to 2M and scramjet above that. Once high enough inlet needs to be closed and internal oxygen provided in stead. Difference between ram and scram jets lies mostly in geometry profile. Pulse jet (used by V1 bombs in WW2) closes inlet with a layer of one way chokes breathing air in between explosion pulses. This layer can be jettison when no longer needed.

Nasa, are you there, any response ?

 

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X-43a

 

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recently scientists managed to make macroscopic nano tubes with a tensile strenghth of 20 gpa while individual strands can reach 63 gpa scientists believe they would need a tensile strenght of 120 GPA in best case to make a space elevator, so nowhere near enough as of yet but it has far superior fundings because of ground apllications and recent developmends are measered in months.
Also the development of rockets is extremly costly and air breathing rockets would be smaller in mass but the increase in technology would not necesairly make them cheaper and have the obvious drawback of more parts that can fail.

 

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This brings up an interesting question (at least for me).

If a vehicle could be made to withstand the incredible heat of friction, is there any theoretical reason that the right type of engine could accelerate the vehicle to greater-than-orbital speed (> 17,500mph) while still in the atmosphere, and then vector off and achieve LEO using almost no on-board fuel or oxidizer?

 

I'm getting some second hand information from Nasa managers commenting on this new venture. They tentatively assign it a code name X-43a ('a' most likely stand from inventor initials ael65). First wave of criticism is directed at project additional complication and possibility of cost overruns, particularly danger because they threaten further postponement of top priority 120GPA space elevator scheduled to be operational in next few decades just pending some fundamental physical breakthroughs. (The cynics like to point out that auto industry is using the same coy to plea against decreasing emission limits for automobiles arguing that there is this marvelous fuel cell technology right behind the corner being developed that will be delayed if funds are directed else ware). Also, because of public funding nature it would be desirable if some crossbreed technology can be developed that would benefit not only space but Earth as well.

In response to this immediate pressures and also having in view a superluminal long horizon I would propose slight modification: just get rid with old clunky pulse jet (Werner von Braun is no longer available to help) and replace it with electromagnetic sled system capable of accelerating 6g (human comfort limit) over 3km to get to initial speed of 0.5M. From there on ram and scram should be able to take over. As an additional benefit such a venture located close to Florida theme parks can count of untold number of tourists willing to try this shorten version of a zero gravity space-ride. For unmanned probes there is still option considered to accelerate at 1000g and reach LEO speed at the end of a runway.

-al

 

-al

x-43a

is this beast

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and what you propose is unattainable as it combines many untested design systems at once. In addition to engineering problems exhibited from magnetic sled...

 

That is typical Nasa thinking: make a laundry list of problems and then expect a poor inventor to solve them all. What happened to faster, cheaper, better ?

Of course it can be done (in a few years):

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With conventional notation for distance traveled during constant acceleration, S, we have: S = (gT^2)/2 and the average speed for constant accleration from 0 to 0.5M is 0.25M = V. Thus, the duration of the acceleration, T, is S/V.

If we take g=32 Feet/ sec squared and M = 1000 ft/sec then the above equation becomes: S = 16 (S/250)^2, which in std quadratic equation form is:

0 = S^2 - 3906S = S(S - 3906) This is very easy to solve as there is no constant term, usually called "C."

I did replace correct 3906.25 with a whole number as my value for M is not exact (could not be as speed of sound depends on temperature of the air) and only interested in quick easy estimates. The S=0 solution is just the pre ignition solution (has not gone any where yet) Thus the length of the acceleration ramp is ~3906 or more like 4km, not your 3km or almost 2.5 miles.

I presume it is an essentially horizontal 2.5 miles. Perhaps in some dry salt flat not far from the equator? Do not want any "bumps" as already at the limit of human accelerations and could come off the rails (or more energy loss with wheels both above and below the rails to hold it on) Now that it has be given considerable kinetic energy without the need to accerate the fuel required for that, how does it get turned more nearly up? Is it slowing down quickly or does some on board rocket fire up just before coming off the end of the ramp?

Instead of being in the thin air 2.5 miles high it is dense surface air. I am not sure there is any advantage, and what there is, if any, is mainly a saving in some vertical launch fuel. The capital cost (that is a continuous cost* - I am not refering to the capital but the interest lost every day) of the magnetic linear accelerators is much higher than that fuel savings. Also surely you do not want a lot of iron mass on the craft you are sending into orbit, just for the accelerating dynamic (lot of energy loss with a dynamic B field near electrical conductors) magnetic field to "grab hold of," so I presume the space craft is attached to a sturdy iron sled (must crash into a sand pile or water lake for economical re use).

This sled is also accelerated to 0.5M and separates at the end of the ramp from the space craft. When the energy required to accelerate this sled is considered, I seriously doubt if any fuel is saved, compared to the standard vertical launch. Note that in the vertical launch much (perhaps more than half of the fuel is burned quickly, so you will have at the surface approximately the same fuel mass traveling at 0.5M as the standard vertical launch has when it is also traveling at 0.5 M, but in much thinner air at an elevated atmosphere.

SUMMARY: I see no advantage to the system you are suggesting. In above it seems to be both more costly and use essentially the same energy, if not more. I may be wrong, but you need to do some realistic analysis, not just rely on your hunches and intuition.
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*Just the copper in the many electro-magnets closed spaced for 2.5 miles is huge static investment, that could be earning interest or more profitably invested, but that copper is only a small part of making and installing a 2.5 mile long linear accelerator and its electrical system (Perhaps powered by a dynamic flywheel generator so as not to also require huge brief power capacity of the electric company's investment, which used less than a minute each month!)

PS I agree that "it could be done." My doubt is based on the high probably that it cost much more and is less efficient than the conventional vertical launch.

 

Just send them up with conventional rockets just like Russia is doing and

NASA will be doing soon. It is much much cheaper to use conventional

rockets than any other type of lifting system that has been designed to

date.

 

Yet another maglev thread! Good debunking of this one Billy, they come up every now and again, here's one I debunked previously;

http://www.sciforums.com/showthread.php?t=64600

The linked article was a bit vague, and didn't mention any numbers, so in my debunking I took it to accelerate to escape velocity, which proved an impossible task. I may have screwed up the numbers a few times too, but all of my calculations came up with such scary numbers it was hard to match them to a guesstimate!

 

Did my highschool physics got rusted ?

S = a*t^2/2 = V^2/2a = 600^2/(2*6*9.81) m/s = 3058 m/s.

OK, I see I took 600 instead of 344/2=172 m/s ( I confused 1200 km/h with 1200 m/s). With that correction S = 251m. Quite a short ramp. (OK, 6g might be too much, I belive that SS is using 3g - then 502m)

Equator would be better, but because of entertaintment value I suggested Florida, just a parallel track beside space shuttle landing strip at JFK space center.

Ramp should be essentionally flat with the last part rising up, let say up to 30 deg (calculation pending). This will initiate the turn, but it is going to be essentially completed by the aerodynamic forces (wings) of the craft.

I would like to get vertical but I'm also afraid of the costs (I was a proponent at some time of setting a 2 vertical cables hanged from 10Km high baloons and let craft use electric tracks to propell through the air. This invention was shot down though). The real advantage here is to get initial speed allowing ram/scram jet to take over. This kind of engine is very simple but doesn't work at low speeds. That is why my initial guess was to use also something simple pulse-jet as initial stage. Remember, em-sled is a substitude solution, after I was force to fend off criticism.

Energy wise em sled will be cheeper per launch (you pay only for 'action' force, not 'action' and 'reaction' as per rocket drives). Then economics comes to how often you want to sent something up.

Think advance sled. Active system instead of iron and with a little wings on top, all remotly (autonomously ?) controlled. It will come off the ramp together with space craft, aid the aerodynamic turning and then gently land at the end of a mission.

Billy T, sorry I can offer only hunch on such a short notice, but I expect that Nasa must have done detail analysis that is out there somewhare, if you are interested enough to look for it. Because it is multidimensional problem: safty-economics-capability-reliability-.... outcome can be very different then initial inkling. However, every man made adventure started with hunches and intuition ....

-al

 

ael65 ... Billy T is right, if you want to take this seriously than do calculate all the physics behind this and the economical foundations... you can approximate the MAGLEV train tracks' cost as a base.

 

What are you crazy ? Do you want me to do 100 man years jobs and mail you 1000 page report ? And after all that you still will be able to point additional 100 aspects of endevour that had not been considered (e.g: impact of tight a launch schedule on a breeding cycle of pink flamingos nesting within down wind trajectory, particularly at the second fool moon of the breading season taking into accont daily moisture accomulation with special attention paid to ....).

 

Yes I am crazy.

If you really believe in something, commit to it fully.

 

I will burn atmosphere in an instant and die...after all my life destiny to go to Mars. After each second spent to conquest that goal. Or...or...I will succeed. That thought that I can succeed, that I can bypass all troubles...all problems begone...to reach my dream of being space. That one thought is enough for me to live and to strive for it, knowing that I may die on the path to it.

So do it...if you truly believe in it.

Do it Ael65!

No age is limit, no words of anyone should stop you, believe in it will your heart and mind...and live for it!

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Wow, that is a one cool picture ? dragon, where can I got more of those. I want to change my screen saver and the galaxy I'm looking at is nowhere to compare with that piece. (seriously)

As to "believe being able to move mountains", well I wished I was not brought up at the end of 20th century: with all the rationalization, critical thinking, responsibility for your action, tolerance to others and all that learned ability to coexist seamlessly within a large population. You measure your goals according to your learned abilities, not other way around. Beside I have other projects to commit: like to save world from crisis and invent perpetum mobile of the second kind.

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-al

 

No. your method is OK, but like me, you made some errors in the intital application.I will switch to your MKS units and after correcting my errors agree the craft comes off the end of a 251m ramp at 172m/s.

If it has wings for turning upwards, they add both weight and more drag (especially later when supersonics if large enough for making the turn up at low speeds earlier). These wings must be strong to survive transit thru the speed of sound shock waves higher up in the air.

Rather than send these wings into orbit, etc, why not simply avoid all the high cost of the magnetic accelerator and get your ram jet up to operational speed with space craft "piggy backed" on top of a more conventional airplane*? Not too hard to get in going half the speed of sound essentially straigth up and a airplane is much cheaper than the magnetic accelerator that can achive v= 172m/s in 251meters.

IMHO, you are not adequately considering the power levels required from the electric system that drives those dynamic magnets. - A hell of big fixed, seldom used, capital cost, I am almost sure. Most attempts to hold a plasma in fusion experiments for even a second store the energy for the magnetic field in a flywheel generator they can charge up slowly - the Princton "stellarator" did I know as I visited it years ago. In our work on the fusion problem, a much smaller effort, at APL/JHU paid for by the US Navy, we had two large motor generators (Lots of rotation energy stored) that came off an scrapped navy mine sweeper.You need to accelerate the space craft to V=172m/sec in t = S/(V/2) = 502/172 = 2.9 seconds That is a high power requirement even if 100% efficiency were possible.

In contrast, the air that the airplane flys thru is free (in contrast to the magnetic ramp) and it can take 1000 times longer to get the space craft upwards headed at 172m/s if that is what the ram jet requires. I.e. operate at hundreds of times lower power levels. High electric power capacity is always very costly. (I doubt, however, if there is any advantage to using an airplane for this compared to simple strap on / drop off solid state "booster rockets" as NASA, The Russian, and everybody else uses.)

Also I think steady burning rockets are more efficient than intermittent pulses of a ram jet. Certainly they place less stress on the space craft, but than may not be too important as it must survive going thru the sound barier's shocks anyway.

SUMMARY: after we got the values correct, I admit the magnetic rail acclerator is not as costly as I initially thought, but still more expensive that a lifting "mother air plane" which could take much longer (lower peak power capacity required) to get the space craft up to ram jet speed and headed upwards. Also a great advantage is that it could carry the space craft up to 30,000 feet into thin air, but then the ram jet probably would not work well. I.e.it still seems to me that your suggestion is quite inferior to what is being done, especailly if you want to stick to the magnetic accelerator and a ground level launch of a ram jet motor. Again you need some real analysis, not just guessing and opinions. Certainly, most good ideas do start that way, but they go nowhere without some analysis that then supports them.
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*Even the huge space shuttle rides on top of an airplane when it moves for one landing field to another.

This does not make much sense to me because you always have both - that is Newton's 3d law. I think what you mean is that most of the rocket's energy is going into the exhaust gas initially (at least from POV of frame at rest with respect to the Earth) Later, when they exhaust velocity is the same as the rocket speed, none is. Kinetic energy is frame dependent. You can always find a frame, POV, in which it is zero. Considering the magnetic coil loss (or thermal losses if superconducting magnets but hard concept for dynamic magnets of an accelerator) and eddy currents induced in nearby conductors, I do not know which would put energy into the KE of the space craft more efficiently. If magnets are powered by big flywheel generator that is spun up for half a day prior to launch there is also energy loss there. In general I think that chemical rockets can deliver huge power levels and get the losses over very quickly and certainly the pulsing ram jet is lower efficieny that a steady burning rocket for accelerating any mass. I think the Germans used them in WWII as ram jet motors are cheap, not for any other reason.

 

They just carry them on belly of huge airplanes...them ramjets. And let em' go at high altitudes.

 

OK, so either way we have carrier plane piggy backing the orbiter. With em-sled this plane gets a kick from accelerator track. In a more traditional design you propose it is going to be more like a regular plane. The carrier plane needs wings, ram-scram engine and should last till let say 20km up. The payload is a regular rocket, no doubt there. At the end we hope it will travel vertically at acceleration 3g supersonically M 7??, where the orbiter will be able to take over. The question is what makes more sense: build a em-tracks with all their complexity or equip carrier plane with standard jet engines that are going to be used till M 2.0 and then need to be retracted and hauled as a dead weight upward in a supersonic regime. (unless this should be 3 tier approach: jetplane + scramjet + rocket). em-sleds are very reliable; they are being used in amusement parks as roller coasters loaded with public on a regular basis.

This is a part I didn't considered. However, total amount of energy in either case is going to be the same (assuming same efficiency). Em sled requires large electric buffer, and flywheels sounds adequate. Perhaps stack of fuel cells can be used since they can provide large current.

That seems to be the case with direction Nasa is taking with Orion

Check latest Scientific American. There is a suggestion there to use pulsed detonation chamber borrowed from the pulse jets as a middle section of a jet engine. Hope to be 5% more efficient.

I admit analysis almost none here. Should I come back to pulse-jet as an initial stage ?

As you pointed out, a rocket engine efficiency at launch approaches 0% and then grows up till maximum when exhaust speed matches vehicle, and then slides down again as speed increases. At start you are just loosing all the energy propelling gas backward. This should be yet another argument to consider em-sleds as the initiator. Jet engine is better matched to the lower speeds then rocket, so jet plane would do already an efficiency improvement.

My bet would be that linear accelerator w/o moving parts, properly designed would be more efficient then any kind of rocket on any day. If you include prolonged electrical energy storage, then I'm less certain.

 

I must be going mad, because Dragon has said something I agree with! ;-)