Author Topic: The Reaction Engines Skylon Master Thread (1)  (Read 708796 times)

Offline Hempsell

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Re: Skylon
« Reply #140 on: 05/13/2011 08:00 am »

Makes sense! One other idea-what about another heat exchanger, from the hot He from the precooler directly to the GH2 from the first heat exchanger it passes through? Might cut the amount of LH2 needed significantly, at the expense of very high temperature hydrogen heat exchangers being needed (but doesn't the preburner already need that)?


I am not quite sure I understand this one.  The precooler (which is staged so is HX1 and HX2) is followed by HX3 in the preburner to further heat the Helium up so it has the power (100ís megawatts) to drive the turbines and pumps, we do not want to do any cooling of the Helium until it has done its work.  It is a classic thermodynamic cycle using the temperature difference between the heating end (HXs 1 to 3) and the cooling end HX 4 and we want to maximise the temperature difference.

Offline MickQ

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Re: Skylon
« Reply #141 on: 05/13/2011 08:43 am »
What about combining the seaplane and trolley ideas with SKYLON riding on a high speed catamaran hull.  As speed increases the hull lifts out of the water on hydrofoil vanes to reduce water drag.  SKYLON lifts off the hull at the appropriate speed, completes the flight and lands normally on a standard runway.  The cat is recovered and re-used.

Ready.  Aim.    ?

Mick.

Offline Carreidas 160

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Re: Skylon
« Reply #142 on: 05/13/2011 09:52 am »
Back a bit; Seaplane SKYLON...
(That would actually be quite a "cute" way to go as I recall seeing a nicely done Brit movie where they were testing a supersonic, stratospheric seaplane. Had a spy screwing things up the but the ending was classic. Still shot of a model of the seaplane on a "flight-stand" with an open Observatory slot and a it aimed at the stars.... Loved that :)

...

Still, the "ekranoplane" concept has possibilites given the work the Soviets did on a similar concept. I still keep coming back to the engine location though...

Randy

Remember the name of the movie? Would like to see that.

By the way, some of the images of the Soviet ekranoplan prototypes you can find on the net actually look a little like Skylon (similar wing placement, canards). On the engine location, couldn't you use them in rocket mode for the take-off run? With the inlets closed the water splashes shouldn't matter that much. Or is the thrust too low in rocket mode to use them like that?

Some facts: the biggest ekranoplan ("the Caspian Sea Monster") weighed 540 tons and got to a top speed of 297 knots... If I wanted launch-assist for Skylon I'd go for one of these.


Offline Joris

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Re: Skylon
« Reply #143 on: 05/13/2011 10:32 am »
Some facts: the biggest ekranoplan ("the Caspian Sea Monster") weighed 540 tons and got to a top speed of 297 knots... If I wanted launch-assist for Skylon I'd go for one of these.



I believe that had a payload of over 400mt, which is more than what Skylon would weigh.

It is currently rusting in a dry-dock, so you may have to rebuild it.
JIMO would have been the first proper spaceship.

Offline Cinder

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Re: Skylon
« Reply #144 on: 05/13/2011 12:56 pm »
What about the water stillness constraints?  And would the ekranoplan carrier really amount to a savings versus classic runway operations?
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Offline tnphysics

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Re: Skylon
« Reply #145 on: 05/13/2011 09:51 pm »

Makes sense! One other idea-what about another heat exchanger, from the hot He from the precooler directly to the GH2 from the first heat exchanger it passes through? Might cut the amount of LH2 needed significantly, at the expense of very high temperature hydrogen heat exchangers being needed (but doesn't the preburner already need that)?


I am not quite sure I understand this one.  The precooler (which is staged so is HX1 and HX2) is followed by HX3 in the preburner to further heat the Helium up so it has the power (100ís megawatts) to drive the turbines and pumps, we do not want to do any cooling of the Helium until it has done its work.  It is a classic thermodynamic cycle using the temperature difference between the heating end (HXs 1 to 3) and the cooling end HX 4 and we want to maximise the temperature difference.

This would be a separate heat exchanger that would operate in parallel (not series) to HX1 and HX2 and their associated turbomachinery. It would do no work, but it would cool air, allowing lower H2 flows-and thus greater airbreathing Isp.

My understanding of it is that there is an abundance of power at these high airspeeds.

Offline Carreidas 160

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Re: Skylon
« Reply #146 on: 05/13/2011 10:42 pm »
What about the water stillness constraints?  And would the ekranoplan carrier really amount to a savings versus classic runway operations?

The awesomeness would negate any cost overruns.

Offline Joris

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Re: Skylon
« Reply #147 on: 05/13/2011 10:46 pm »
What about the water stillness constraints?  And would the ekranoplan carrier really amount to a savings versus classic runway operations?

It would save just 150m/s DeltaV and no height advantage.
This is 150m/s that would be done by a very efficient form of propulsion (~3km/s^2, I think).
So no, not really.
JIMO would have been the first proper spaceship.

Offline lkm

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Re: Skylon
« Reply #148 on: 05/14/2011 03:10 pm »
Looking at the Project Troy vehicles and Nautilus-X they would seem to be quite similar in nature and a good basis for an international consensus on a future architecture. They seem to share modular in orbit construction supported by a mix of HLV and MLV launches, ripe for internationalisation, and Skylon.
At what point of the  Skylon development program does its future existence become an acceptable, or necessary, assumption to make in conducting these sorts of studies, or rather what milestones need to be passed before this thread moves from advanced concepts to commercial space flight?

Offline jee_c2

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Re: Skylon
« Reply #149 on: 05/14/2011 07:24 pm »
What about the water stillness constraints?  And would the ekranoplan carrier really amount to a savings versus classic runway operations?

It would save just 150m/s DeltaV and no height advantage.
This is 150m/s that would be done by a very efficient form of propulsion (~3km/s^2, I think).
So no, not really.
The ekranoplane was not suggested because of the added velocity, but rather instead of the runway (so Skylon could be operated from the sea (lkake) also.

Hmm, perhaps one more aspect: could take off from the equator. (see Sea Launch, same benefit).
And because it would have the biggest world wide runway,(so could start from several locations, not bound to a specific air(space)port.

Offline mlorrey

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Re: Skylon
« Reply #150 on: 05/14/2011 07:38 pm »
Back a bit; Seaplane SKYLON...
(That would actually be quite a "cute" way to go as I recall seeing a nicely done Brit movie where they were testing a supersonic, stratospheric seaplane. Had a spy screwing things up the but the ending was classic. Still shot of a model of the seaplane on a "flight-stand" with an open Observatory slot and a it aimed at the stars.... Loved that :)

...

Still, the "ekranoplane" concept has possibilites given the work the Soviets did on a similar concept. I still keep coming back to the engine location though...

Randy

Remember the name of the movie? Would like to see that.

By the way, some of the images of the Soviet ekranoplan prototypes you can find on the net actually look a little like Skylon (similar wing placement, canards). On the engine location, couldn't you use them in rocket mode for the take-off run? With the inlets closed the water splashes shouldn't matter that much. Or is the thrust too low in rocket mode to use them like that?

Seaplanes and launch vehicles don't mix well. Takeoffs and landing from water are extremely brutalizing to a fuselage, seaplane hulls are extremely ruggedized and experience accelerated materials fatigue even then, and most of all, are significantly heavier. A vehicle that puts mass fraction above all can't afford a seaplane hull.
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Offline Cinder

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Re: Skylon
« Reply #151 on: 05/14/2011 07:43 pm »
Not only that, but are there really that many places where the water is reliably still enough, often enough to make it an advantageous formula over classic runways?  I've got a vague memory of the Ekranoplan being fairly restricted due to this.  Vague memory of it being basically restricted to that one inland lake/sea.
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Offline 93143

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Re: Skylon
« Reply #152 on: 05/14/2011 07:48 pm »
The ekranoplane was not suggested because of the added velocity, but rather instead of the runway (so Skylon could be operated from the sea (lkake) also.

So you want to buy and operate/maintain a giant ground-effect aircraft, deal with the adverse effects of the marine environment on both vehicles, and accept the headaches of having to load the orbiter on top of the carrier at a seaside dock every time, all to avoid building a runway?

There are plenty of good spots for runways near the equator.  Also remember that in a pinch, Skylon can self-ferry...

It may also be worth noting that the maximum speed quoted earlier for the Ekranoplan was 40 km/h less than Skylon's rotation speed.  Without knowing what the limiting factor was, it's difficult to tell if simply firing Skylon's engines would solve this issue...

Offline jee_c2

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Re: Skylon
« Reply #153 on: 05/15/2011 08:54 pm »
No, I don't really think, that using an ekranoplan like carrier is surely a good idea for launching the Skylon.

Earlier conversation in the thread was touched the problem of a landing gear (needed too much, thus adding too much weight) for such a big and heavy airplane like the Skylon. Mostly that led to the seaplane idea, not the runway problem.


It may also be worth noting that the maximum speed quoted earlier for the Ekranoplan was 40 km/h less than Skylon's rotation speed.  Without knowing what the limiting factor was, it's difficult to tell if simply firing Skylon's engines would solve this issue...

Probably you mistyped 40 km/h (instead of 400 km/h). This is, what I've found for the biggest ekranoplan on Wiki:
"... This led to the development of the "Caspian Sea Monster", a 550-ton military ekranoplan.[3] Although it was designed to travel a maximum of 3 m (9.8 ft) above the sea, it was found to be most efficient at 20 m (66 ft), reaching a top speed of 300 kn (350 mph; 560 km/h) (400 kn (460 mph; 740 km/h) in research flight)."
http://en.wikipedia.org/wiki/Ground_effect_vehicle

About the wave height restrictions: I've read 5m height was ok for take off and landing on water for that "monster". (now I don't find the page to link, sorry).

Anyway, what do you think: the landing gear mass is also an item to minimize (to get better LEO capacity). So what could be the best solution?

Offline 93143

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Re: Skylon
« Reply #154 on: 05/16/2011 01:14 am »
Probably you mistyped 40 km/h (instead of 400 km/h).

Nope.  From previous posts:

our rotation speed is around 590 km/hr
Some facts: the biggest ekranoplan ("the Caspian Sea Monster") weighed 540 tons and got to a top speed of 297 knots...

297*1.852 = 550 km/h

Skylon rotation speed = 590 km/h

590 - 550 = 40 km/h.

They've already gotten the undercarriage to a reasonable weight.  Adding a whole other vehicle, with the extra headaches I mentioned previously, probably won't help.

Offline MarkZero

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Re: Skylon
« Reply #155 on: 05/16/2011 08:23 am »
Ok, so to sum this up a bit.

A simple floating seaplane-Skylon would not work because you cannot go fast enough on water to get to rotation speed and even if you could, it would require ruggedization of the fuselage to withstand the stresses from the water, which would add too much weight. An ekranoplan-Skylon could be able to get to rotation speed but would also require the same weight adding ruggedness and also modifications to aerodynamics that would probably make it less efficient at altitude, and more difficult to make it survive re-entry.

An ekranoplan "launch sled" might be doable, but would add quite a bit of cost & complexity compared to landing gear & runway, and would not have very much benefit. It would also be very weather sensitive to operate. And in my opinion as with any launch sled it would not be as awesome as the current design because it would no longer be truly single stage.

So yeah, let's let this seaplane-Skylon idea (of mine, unless there was a post earlier that I missed) sink.

Offline Hempsell

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Re: Skylon
« Reply #156 on: 05/16/2011 09:11 am »

Makes sense! One other idea-what about another heat exchanger, from the hot He from the precooler directly to the GH2 from the first heat exchanger it passes through? Might cut the amount of LH2 needed significantly, at the expense of very high temperature hydrogen heat exchangers being needed (but doesn't the preburner already need that)?


I am not quite sure I understand this one.  The precooler (which is staged so is HX1 and HX2) is followed by HX3 in the preburner to further heat the Helium up so it has the power (100ís megawatts) to drive the turbines and pumps, we do not want to do any cooling of the Helium until it has done its work.  It is a classic thermodynamic cycle using the temperature difference between the heating end (HXs 1 to 3) and the cooling end HX 4 and we want to maximise the temperature difference.

This would be a separate heat exchanger that would operate in parallel (not series) to HX1 and HX2 and their associated turbomachinery. It would do no work, but it would cool air, allowing lower H2 flows-and thus greater airbreathing Isp.

My understanding of it is that there is an abundance of power at these high airspeeds.

OK I see what you mean now. The problem is that it would reduce the energy from the airflow into the Helium which is where we need it and nowhere to we have too much power HX3 is always doing some top up. Also the "excess" hydrogen is not wasted as it produces propulsion in the ramjet and even when just venting, being hot hydrogen, it can be made to produce significant thrust so there is little drive to minimise it from its current level.

Offline jee_c2

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Re: Skylon
« Reply #157 on: 05/17/2011 07:22 pm »
590 - 550 = 40 km/h.
I see, sorry, I misuinderstood that earlier post of yours. Although it is also written higher maximum speed (740 km/h for research flight), but I'm almost absolutely convinced, that the sea-spaceplane concept is not good.

Anyway, about this landing gear weight issue - is there any good solution, any good idea about it?

Offline Joris

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Re: Skylon
« Reply #158 on: 05/17/2011 07:28 pm »
Anyway, about this landing gear weight issue - is there any good solution, any good idea about it?

Maybe something that the U-2 spy-plane used?
Two of the four wheels dropped after take-off.
Would allow you to have a quite heavy landing gear capable of emergency landings right after take-off, and you don't need to carry them all the way to orbit.
JIMO would have been the first proper spaceship.

Offline RanulfC

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Re: Skylon
« Reply #159 on: 05/17/2011 07:59 pm »
Back a bit; Seaplane SKYLON...
(That would actually be quite a "cute" way to go as I recall seeing a nicely done Brit movie where they were testing a supersonic, stratospheric seaplane. Had a spy screwing things up the but the ending was classic. Still shot of a model of the seaplane on a "flight-stand" with an open Observatory slot and a it aimed at the stars.... Loved that :)

Randy

Remember the name of the movie? Would like to see that.
Not a clue... Came in half-way through and never saw it again wish I had or someone has with a memory :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

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