Why do you aerospace engineers have such a hard time making spacecraft?

[Oomair]

isnt possible to make cost efficient spacecraft by putting multiple types of rockets on a ship which can then alternate rocket engine at different levels of the atmosphere and eventually escape into space?

 

[russ_watters]

Lots of engines? Sounds expensive...

 

[FredGarvin]

isnt possible to make cost efficient spacecraft by putting multiple types of rockets on a ship which can then alternate rocket engine at different levels of the atmosphere and eventually escape into space?

Let's start with the easiest question for you...Are you referring to manned or non-manned space flight?

Every engine that gets put on an aircraft has to get certified (expensive). Every engine has to have its associated components (weight). Every engine costs money to make (again, expense). The more engines you have the more complicated the control system is (cost)...There are a whole lot of tradeoffs to consider other than an engine's Isp in a vehicle design.

 

[Janus]

Lots of engines? Sounds expensive...

It also sounds inefficient, as the rocket engines not in use at a given time just become extra dead weight that the engine in use has to lift

 

[D H]

isnt possible to make cost efficient spacecraft by putting multiple types of rockets on a ship which can then alternate rocket engine at different levels of the atmosphere and eventually escape into space?

This is exactly what we do right now. We do not use a single-stage-to-orbit. The systems that carry vehicles from the Earth's surface to space comprise a number of rockets. Multiple stages are needed because a single-stage-to-orbit vehicle would need to carry its entire empty structure all the way to orbit. With present fuel technologies, doing so be very expensive.

 

[Danger]

There is a compromise approach, but it's still not as good as dropping dead stages. Variable-geometry nozzles such as the (still experimental?) linear aerospike can operate at peak efficiency throughout the climb. That doesn't resolve the issue of all the dead weight, but jettisonable fuel tanks would help.

 

[gaming_addict]

The most efficient I'm thinking right now at the moment is the strategy made by Scaled Composites for the X-Prize competition. Have an aircraft carry the spacecraft from high altitudes and launch it from there. I think the Antonov An-225 could do just that for heavier manned orbital flights.

But maybe in the future, an aircraft could be made just for that and could cruise above 70,000 ft and still carry very heavy payloads, that makes a good launching platform. Instinctively, this craft would be BWB or possibly a high aspect ratio flying wing with extended booms for elevator pitch control, that makes for a high L/D craft with high altitude capability with excellent structural integrity for carrying heavy payloads.

 

[FredGarvin]

There is a compromise approach, but it's still not as good as dropping dead stages. Variable-geometry nozzles such as the (still experimental?) linear aerospike can operate at peak efficiency throughout the climb. That doesn't resolve the issue of all the dead weight, but jettisonable fuel tanks would help.

There is no aerospike that has flown to my knowledge. There are engines that have movable skirts to help compensate for altitude, but not to the extent of the spike.

 

[D H]

The most efficient I'm thinking right now at the moment is the strategy made by Scaled Composites for the X-Prize competition. Have an aircraft carry the spacecraft from high altitudes and launch it from there. I think the Antonov An-225 could do just that for heavier manned orbital flights.

Launching a vehicle from an aircraft worked for SpaceShipOne precisely because it was only a suborbital vehicle. SpaceShipOne had a maximum specific energy of about 1 megajoule. Compare this to a vehicle in low Earth orbit, which has a specific energy of 32 megajoules or more. Launching a vehicle from an aircraft doesn't buy much capability in terms of getting a spacecraft into orbit. The first stage would still be needed. Much better is to make the various stages completely reusable (Rocketplane-Kistler K1, Space-X Falcon-9).

 

[Oomair]

what I am trying to say is that, why doesn't NASA develop manned vehicles with multiple types of engines, for example, the ship uses let's say engine A to get to one point of the atmosphere,

then engine A is shut off but not broken off the ship, then you activate engine B, C, and eventually escape into space

that way the engines are saved so NASA doesn't have to waste money to make new ones

 

[Brinx]

Oomair, many reasons why it's not done like that were already given in the previous answers you got...

 

[D H]

what I am trying to say is that, why doesn't NASA develop manned vehicles with multiple types of engines, for example, the ship uses let's say engine A to get to one point of the atmosphere,

then engine A is shut off but not broken off the ship, then you activate engine B, C, and eventually escape into space

that way the engines are saved so NASA doesn't have to waste money to make new ones

The crucial phrase here is "but not broken off the ship". If the vehicle doesn't discard spent stages it has to haul all that dead weight into orbit. The http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation" says this is cannot be done. It would be better to have a single-stage-to-orbit vehicle (which we can't do yet) than a multi-stage-to-orbit that doesn't discard spent stages. Moreover, returning this dead weight to Earth will be a considerable challenge. The return vehicle will have to be a lot heftier to be able to keep that awkward weight under control when it hits the atmosphere at Mach 25. That's even more dead weight that has to be hauled into orbit.

 

[Danger]

Oomair, you might be getting misled by some ideas that have been kicking around for atmospheric machines, such as taking off with turbojets and switching to scramjets when supersonic. Those things are not intended to go orbital, and they don't have to carry an oxydizer.

 

[gaming_addict]

Oomair, you might be getting misled by some ideas that have been kicking around for atmospheric machines, such as taking off with turbojets and switching to scramjets when supersonic. Those things are not intended to go orbital, and they don't have to carry an oxydizer.

Oomair may have a point, but not literally with multiple engines. I've read about some 'single stage' concepts put forth by reputable aircraft companies. One of them actually envisioned a turbojet that 'morphed' and doubled as rocket engine. The turbojet seemed to close it's inlet, compressor and combustion area, and used the nozzle section as the rocket engine.

I was thinking that turbojets are rather complex and heavy. So I might propose a ramjet instead that morphs to scramjet, and finally morphing to rocket engine to reach orbit. Scramjet are indeed not intended to go orbital and that's when the rocket engine or 'rocket mode' takes over.

The idea understandably, makes the vehicle carry much less oxidizer needed than would a pure-rocket design, that enormous fuel weight saved could directly translate to greater payloads carried and of course, much improved economy of space flights. The challenge now is designing a morphing engine that is efficient in wide range of flight regimes as well as light in weight.

There has been real plans to use the the scramjet for use with single stage orbital vehicles, but scramjet technology and hypersonic flight is still relatively early as of now. There's not even one manned flight conducted to date.

@D H, the energy comparison, is very enlightening to know, thanks, so that would make aerial launches very much insignificant gain in energy

 

[Cyrus]

Hypersonic research has been going on since the 60's gaming_addict. The problem has been finding materials that will survive the high viscous heating.

 

[Oomair]

ok one thing i want to get straight in my head here is that does a space shuttle that is returning to orbit just dive into orbit at a high speed and makes a landing like a plane or does it stay in a suborbital area for a few hours by slowly coming down each atmospheric level so that the heat doesn't dissolve it?

 

[gaming_addict]

ok one thing i want to get straight in my head here is that does a space shuttle that is returning to orbit just dive into orbit at a high speed and makes a landing like a plane or does it stay in a suborbital area for a few hours by slowly coming down each atmospheric level so that the heat doesn't dissolve it?

It takes a little over an hour to start from deceleration burn to landing. And yes, you are right with your 2nd statement.

-It starts by deceleration burn
-Skips over the upper atmosphere, much like a skipping stone thrown over the surface of a lake
-By maintaining high angle of attack, you create a 'lot of drag' and the glide path steepens <-do that if you think you might overshoot your target landing area, conversely, you reduce angle of attack if you feel like coming short.
-You could also do a series of 'S-Turns' or steep break turns left and right to bleed more speed if you think you might overshoot
^^All of the above maneuvers are done above 200,000 ft traveling at hypersonic velocities.

When you have gone below hypersonic at lower altitudes, the glide bath then becomes more steep.

So to summarize, glide path during high altitude hypersonic phase is relatively shallow, done at high angle of attack(to expose the more heat resistant bottom tiles) and to experience the least heating possible(least aerodynamic pressures) but at a longer period of time. Once the craft have gone supersonic, lower altitude, and nearing the landing area, that's when the glide path becomes very steep, to have good speed for landing, and of course to make up for the space shuttle's very poor aerodynamic efficiency :)

 

[FredGarvin]

Oomair may have a point, but not literally with multiple engines. I've read about some 'single stage' concepts put forth by reputable aircraft companies. One of them actually envisioned a turbojet that 'morphed' and doubled as rocket engine. The turbojet seemed to close it's inlet, compressor and combustion area, and used the nozzle section as the rocket engine.

I was thinking that turbojets are rather complex and heavy. So I might propose a ramjet instead that morphs to scramjet, and finally morphing to rocket engine to reach orbit. Scramjet are indeed not intended to go orbital and that's when the rocket engine or 'rocket mode' takes over.

You really should be careful with the words you choose. I have been on a couple of programs that looked into hybridization between air breathing and rocket propulsion systems. That's exactly what they are, hybrids. The whole "morphing" thing, other than sounding cool, is a pipe dream brought about, mostly, by people looking for government research funding. I can imagine my Chevy Blazer morphing into a Ferrari when I want to go into "race car" mode. You're saying the same thing.

I would challenge you to look at the weight of a turbojet versus the combined weight of a thruster package and the associated turbo pumps and delivery systems.

The idea understandably, makes the vehicle carry much less oxidizer needed than would a pure-rocket design, that enormous fuel weight saved could directly translate to greater payloads carried and of course, much improved economy of space flights. The challenge now is designing a morphing engine that is efficient in wide range of flight regimes as well as light in weight.

Oh yeah...those pesky details we have to think about I guess. Morphing...light...efficient over a wide operating range...That's not a challenge. That's unrealistic dreaming.

There has been real plans to use the the scramjet for use with single stage orbital vehicles, but scramjet technology and hypersonic flight is still relatively early as of now. There's not even one manned flight conducted to date.

Considering that the first real scramjet model research craft testing was in 2002 and then 2004, it may be a bit of a stretch to say "we haven't even had a manned flight yet." There's at least a couple of decades of research and development before we see anything close to a manned flight.

 

[gaming_addict]

Yep, that 'hybrid' term didn't come to mind so I used 'morph' instead. When I meant the 'morphing' thing, here's what I meant:

http://en.wikipedia.org/wiki/Pratt_&_Whitney_J58

That's a real example of an engine that 'morphed' into another, from a turbojet into ramjet. So 'hybrid' it is! Sorry I'm not a native speaker so I could get lost with words :)

I would challenge you to look at the weight of a turbojet versus the combined weight of a thruster package and the associated turbo pumps and delivery systems.

I know one of them will be heavier(the turbojet will be the lighter in weight, I assume), and I presume you'd say it won't matter if I used ramjets or turbojets. But I prefer using the ramjet because, it will be used from high subsonic to mach 4 in which, a ramjet will by far outperform a turbojet in thrust levels. Turbojets can only match a ramjet in reheat but it becomes so inefficient

But you're right, these things, ramjet to scramjet, then rocket, is still decades away.

My best bet at present would still be a BWB because it can be stiffened so easily and made very strong. Thus a very light body and yet strong could be made, making single stage flight possible and reentries safer.

 

[D H]

-It starts by deceleration burn
-Skips over the upper atmosphere, much like a skipping stone thrown over the surface of a lake ...

This is all wrong. The Shuttle has only done a skip reentry in simulations. It has never done one in reality. Skip reentry has a very low Technology Readiness Level (TRL 3, to be precise). It is one of the many technologies that need to be beefed up considerably before we even consider sending people to Mars.

 

[FredGarvin]

Yep, that 'hybrid' term didn't come to mind so I used 'morph' instead. When I meant the 'morphing' thing, here's what I meant:

http://en.wikipedia.org/wiki/Pratt_&_Whitney_J58

That's a real example of an engine that 'morphed' into another, from a turbojet into ramjet. So 'hybrid' it is! Sorry I'm not a native speaker so I could get lost with words :)

The thing about the J58 is that it "morphs" into a different version of the same class of engine, i.e. air breathing. It's a big difference from trying to go between air breathing and non-air breathing. The technical difficulties that immediately come to mind to marry the two is pretty substantial.

 

[Danger]

I don't know how practical it would be, but my approach would be to use an air-breathing rocket with a variable geometry nozzle and something like a APU turbine to run the compressor. At ram speed, the compressor could be bypassed, then cut in the oxydizer pumps when the air runs out.
Plausible, Fred?

 

[FredGarvin]

I don't know how practical it would be, but my approach would be to use an air-breathing rocket with a variable geometry nozzle and something like a APU turbine to run the compressor. At ram speed, the compressor could be bypassed, then cut in the oxydizer pumps when the air runs out.
Plausible, Fred?

If I understand you correctly, the first two issues would be

1) Exhaust gas temps from the rocket would be waaay too high for any known made turbine to date. You would have to make some pretty big leaps in materials to do that. The existing rocket chambers are made of pretty exotic stuff like Columbium (Niobium) and Rhenium. Very tough stuff to manufacture parts with let alone complex geometries like a turbine.

2) Getting the variable nozzle to be effective over a wider altitude range (that is a very realistic goal to shoot for).

 

[Danger]

Thanks for the response, Fred. You did apparently misunderstand about item #1, though. The rocket would be just a rocket, with no turbine or compressor inherent to its design. The compressor would be a separate structure which could be ducted into the system with a bypass circuit to force-feed the engine at low speed. With ram speed attained, the diverter valve would be flipped to 'straight-through' from the intake to the rocket. I was thinking of an aircraft APU or electric motor to power it, rather than tapping into the rocket.

 

[gaming_addict]

This is all wrong. The Shuttle has only done a skip reentry in simulations. It has never done one in reality. Skip reentry has a very low Technology Readiness Level (TRL 3, to be precise). It is one of the many technologies that need to be beefed up considerably before we even consider sending people to Mars.

Nice to know. I only experienced the skipping portion in X-plane shuttle simulation, it has way too much speed to start with(perhaps, very little fuel for reentry rocket burn).. I followed everything you read in books with success but it never mentioned the skipping part.. In x-plane you have to hand fly all the reentry phase up to touchdown, and I have a success rate of 3 of 10 attempts. I either crashed or went too short or overshot Edwards AFB :)

Thanks for the response, Fred. You did apparently misunderstand about item #1, though. The rocket would be just a rocket, with no turbine or compressor inherent to its design.

Same here, one air-breathing hybrid(ramjet/scramjet) but my rocket would be an entirely separate unit located in the rear. The rocket nozzles when not in use will be covered by disposable/detachable aerodynamic fairings. Even the ramjet/scramjet can be discarded and reused. But like it is, the technological hurdle is the hybrid ramjet/scramjet. For now, very light weight BWB(with excellent fuel fraction) and aerospike nozzles are within reach.

But I have to ask this time, maybe we are thinking of fuel economy of space flights, but do they contribute significantly to cost of space flights or is the maintenance/manufacture of space vehicles or other things?

 

[FredGarvin]

Thanks for the response, Fred. You did apparently misunderstand about item #1, though. The rocket would be just a rocket, with no turbine or compressor inherent to its design. The compressor would be a separate structure which could be ducted into the system with a bypass circuit to force-feed the engine at low speed. With ram speed attained, the diverter valve would be flipped to 'straight-through' from the intake to the rocket. I was thinking of an aircraft APU or electric motor to power it, rather than tapping into the rocket.

I got you now. I can't say it's unfeasible technically. It may tough to match an APU big enough to drive a reasonable sized compressor and not go through the roof on weight.

I would have to figure out the entire cycle though and where you would insert the compressor to help the rocket at low speeds. I'm just not seeing that being any help. Do a sketch...those are always a huge help.

 

[Danger]

Will do. It'll take a while, though, because I'll be using Illustrator. That entails filtering it through Photoshop in order to get a format that Imageshack will accept. I did that crappy little turbine sketch in Paint, but I hate that program.

 

[Astronuc]

http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=14589
The plume physics behind aerospike nozzle altitude compensation and slipstream effect

J. H. Ruf and P. K. McConaughey (NASA, Marshall Space Flight Center, Huntsville, AL)
AIAA-1997-3218
AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 33rd, Seattle, WA, July 6-9, 1997

http://www.aerospaceweb.org/design/aerospike/losses.shtml

Test flight of aerospike engine - see figures 5 & 6
http://www.maecourses.ucsd.edu/mae155a/nlv.pdf

I am not sure that aerospikes can be scaled up for large rocket motors though. There comes a point where storage of cryogenic hydrogen becomes in issue, which is why Saturn V was based on kerosene/LOX.

Back in the days of large thermonuclear devices, the Pentagon embarked on a program for nuclear propulsion to launch them. Then the guys at the Livermore and other labs got innovative and the size of the TN's got smaller such that conventional rockets could launch them. Then nuclear propulsion was realigned to interplanetary travel - which then died in the early 1970's.

As for power, many systems use a power head or bleed and feed system.

http://shuttle.msfc.nasa.gov/SSME.cfm

http://www.engineeringatboeing.com/dataresources/SpaceShuttleMainEngineThirtyYearsOfInnovation.doc

See also - http://www.space.com/businesstechnology/technology/sli_cobra_020904.html

 

[Danger]

Hey, Fred... I finally got a chance to do that sketch up. As you can see, I didn't go into any detail; it's just an overview of what I have in mind. I didn't bother drawing the 3rd configuration, which seals the combustion chamber from atmosphere for straight rocket operation.
"[IMG[/URL]

 

[FredGarvin]

Nice drawings Danger. You even included the preheat/cooling coils on the nozzle.

I think the idea is feasible. There would be a couple of tricky spots to it if it ever got off the ground (pardon the pun):

- You would have an aerodynamic flowpath into the top of the rocket chamber. That flow would be pretty tough to have behave. It would take some doing but not impossible.

- The typical smaller rocket engine chamber pressure is around 150 psia (from what I have seen). That would mean you would either have to size the compressor to have the same final pressure rise or increase the wall thickness on the chamber which would usually mean huge dollars.

- The compressor section would have to decouple some how from the chamber. Typical rocket chamber temps are wicked hot*. The thermal soakback would be tremendous. Thermal management in general would be tough.

* Technical engineering term for high temperature.[/size]

- The only other thing I can think of off the top of my head is how would this thing run when in the air breathing mode? I don't think it would be easy to get the equivalent burn out of the air breathing side versus the rocket side simply because the air is a different oxidizer. Would you get the same burning characteristics out of the same fuel using two very different oxidizers? I don't know.

Still, I don't think it would be beyond anyone to try this configuration. I think the toughest part would be to sell someone to fund it!

 

[gaming_addict]

I agree with some points by FredGarvin. Modern rockets must generate incredible chamber pressures to attain the desired efficiency and higher exhaust speeds. In order to 'practically' hybridize a rocket, some compromise has to be made and it's not going to be good on rocket efficiency. The compromise in efficiency may not justify the weight savings, complexities or even potential reliability issues with the design

For what it's worth, jet engines are not massive engines. I would keep the air breathing engines completely separate from rocket engines.

I might even improve on it that the turbojet/ramjet/scramjet package, hybrid or not, will be slung beneath the launch vehicle with it's own set of wings blending with the underside to not add to drag, it will detach once for example, mach 20 is reached and will glide back to Earth and land on a runway.

For convenience, launch site will be relocated to Guam or Hawaii. So by the time the vehicle is over US mainland, it should've reached mach 20(hopefully) so the jet package glider can land in an airport, refueled, and flown on it's own power to east coast, then transported(by sea or air) back to the launch site again.

 

[Danger]

* Technical engineering term for high temperature.[/size]

Thanks for the thorough analysis, Fred. Some of those things never crossed my mind at all.

(I should explain at this point that I 'invented' this thing about 30 years ago to power a mach 8 fighter/bomber that I also 'invented' for an SF novel which will never see daylight. It was intended to operate at 28,000° C, so could actually plasmacize ram air for thrust rather than relying upon the onboard hydrogen supply. The whole thing, of course, depended upon a fictional amorphous al/ti/polyurothane alloy with a failure temperature of 30,000°.
There was no combustion chamber; rather it used a 'thrust block' of the same material perforated like the core of a NERVA, heated by a 10MW neutral hydrogen accelerator, through which the propellant flowed.
The compressor was to be driven by a hugely powerful electric motor drawing from a pair of SNAP generators, later replaced by a 20MW cobalt 60 beta-source generator. It didn't feed to the engine, but to a gas separation system that pulled the hydrogen out and sent it to the fuel storage. The engine turbopump drew from that. There was no oxydizer, because it worked by pure thermal expansion.
All that I'm trying to do now is 'downgrade' the idea to see if it could be done with actual technology.)

I'm concerned about the aerodynamics of the intake ducting, since it can't be properly efficient for both configurations. I figure to maximize it for ram mode, since the compressor can compensate somewhat for bad flow in turbo mode.
The thermal soakback never crossed my mind, and I haven't a clue what to do about it other than either routing the fuel or other coolant around the compressor, or just putting it a lot farther away from the combustion chamber.
The different operating characteristics with different oxydizers also didn't occur to me. I'd have a pretty good idea of how to deal with it in an IC engine, by fiddling with the mixture and timing, but I really don't know nearly enough about rockets or jets to have clue in this case.
I just noticed while referring back to your post that Gaming Addict has weighed in while I was composing this. I'll just go ahead and post this, then read that one.

 

[Danger]

Good points, GA. I particularly like the 'gliding booster' idea. The only problem point that I can immediately think of, which is probably quite surmountable, is that the recess into which the booster fits for 'blending into the underside' could give pretty nasty aerodynamics for the re-entry phase. Perhaps a top-mount design would be more appropriate?

 

[gaming_addict]

The 'gliding booster' will have a perfectly 'flat top' design so the launch vehicle's (LV) underside, need not be specially shaped to maintain aerodynamic efficiency. It only has to have a flat bottom to have a smooth mating of the LV and glider.

The 'flat top' is actually a common design for hypersonic designs nowadays. In addition, the glider's wings with a span that is wider than the LV will also serve as additional lift source for the whole booster/launch package. When the glider has detached from the LV, the LV's main lift source will be from it's lifting body design and it's small wings that will be used to control the LV in reentry and landing.

The glider will be physically larger than the LV, but nearly all it's fuel will come from the LV, with a little jet fuel left for landing.

Nice idea for a fully reusable, fuel efficient launch package, but think that for a manned launch package, the glider, will be a large craft, may be larger than XB-70 bomber and has to fly at hypersonic speeds. You may even think of it as the mothership, instead of the LV! Given that we are no longer in a Cold War era, it may take decades to become practical :)

So yeah, maybe that answers the title of this thread, why not? Because the threat of a space-based war is no longer a possibility, at least for now.. The space program naturally won't be the highest of priorities.

 

[Danger]

Hmmm... sounds like a few minutes of work have gone into planning this.
I misunderstood about the mating surfaces; I thought you meant that the booster's bottom blended into the lines of the payload.

 

[FredGarvin]

I might even improve on it that the turbojet/ramjet/scramjet package, hybrid or not, will be slung beneath the launch vehicle with it's own set of wings blending with the underside to not add to drag, it will detach once for example, mach 20 is reached and will glide back to Earth and land on a runway.

No offense, but you're getting silly now. Theoretically it's fun to say we'd like to do something, but there is no way, currently, that one would ever get an engine with a rotating group to survive anywhere near M20. We're having a tough enough time at M4.

Let's not get too carried away with wet dreams and stick to what is plausible. This forum is not meant to be a sounding platform for sci-fi ideas and the like.

 

[gaming_addict]

No offense, but you're getting silly now. Theoretically it's fun to say we'd like to do something, but there is no way, currently, that one would ever get an engine with a rotating group to survive anywhere near M20. We're having a tough enough time at M4.

Let's not get too carried away with wet dreams and stick to what is plausible. This forum is not meant to be a sounding platform for sci-fi ideas and the like.

Read below! You really offended me by making me sound stupid without first reading my whole idea and opinion!

I DISPROVED MY OWN IDEA! BACKTRACK TO POST #34, 4TH PARAGRAPH!

Nice idea for a fully reusable, fuel efficient launch package, but think that for a manned launch package, the glider, will be a large craft, may be larger than XB-70 bomber and has to fly at hypersonic speeds. You may even think of it as the mothership, instead of the LV! Given that we are no longer in a Cold War era, it may take decades to become practical :)

And here's another by yours trully:

One of them actually envisioned a turbojet that 'morphed' and doubled as rocket engine. The turbojet seemed to close it's inlet

and that answers his rantings about:

..but there is no way, currently, that one would ever get an engine with a rotating group to survive anywhere near M20. We're having a tough enough time at M4.

Whoever in his right mind would expose a helpless turbine engine in the ferocious speeds of mach 20? And don't you think closing an inlet is impossible, the Concorde engines does it during emergencies without drag penalty.. :zzz:

We do have an engine that goes from full stop to mach 4, the J-58 turbojet/ramjet hybrid used by SR-71, unfortunately, the SR-71 cannot take the heat from mach 4 flight.

Please don't try to sound smart by replying at warp factor 9.999.. Read carefully, understand, maybe research first... ok? Otherwise, you could sound quite the opposite of what you think you are

 

[FredGarvin]

Read below! You really offended me by making me sound stupid without first reading my whole idea and opinion!

I DISPROVED MY OWN IDEA! BACKTRACK TO POST #34, 4TH PARAGRAPH!



And here's another by yours trully:



and that answers his rantings about:



Whoever in his right mind would expose a helpless turbine engine in the ferocious speeds of mach 20? And don't you think closing an inlet is impossible, the Concorde engines does it during emergencies without drag penalty.. :zzz:

We do have an engine that goes from full stop to mach 4, the J-58 turbojet/ramjet hybrid used by SR-71, unfortunately, the SR-71 cannot take the heat from mach 4 flight.

Please don't try to sound smart by replying at warp factor 9.999.. Read carefully, understand, maybe research first... ok? Otherwise, you could sound quite the opposite of what you think you are

You are the one that is throwing out fanciful "ideas" that have no premise in current capabilities. My comment was in regard to the fact that we like to try to keep this board on a professional level. Having little "I think it would be cool to do this" conversations with no earthly technical clue as to what you are talking about is not a discussion. It's a circle jerk. Most of the stuff you are spouting off about belong in the skepticism and debunking forum. I really don't care if I offended you or not.

Any time you want to put up your video game playing experience versus my actual experience, I'll be more than happy to oblige.

 

[berkeman]

Please don't try to sound smart by replying at warp factor 9.999.. Read carefully, understand, maybe research first... ok? Otherwise, you could sound quite the opposite of what you think you are

gaming_addict,

You need to mellow your tone. You are out of line when you are telling Fred to "maybe research first".

Please confine your posts here in the technical forums of the PF to well-grounded scientific ideas and questions.

 

[gaming_addict]

You are the one that is throwing out fanciful "ideas"

So I am, and I admit it. But I've also let everyone know on post 34 paragraph 4 that my idea is fanciful. I thought you would agree, I bet you would!

Anyway, I hope it ends here, I don't want to go much off topic and waste time. I apologize to all for wasting some of your time.


<< post edited a bit by berkeman to keep the discussion on-topic >>

 

[gaming_addict]

Hmmm... sounds like a few minutes of work have gone into planning this.
I misunderstood about the mating surfaces; I thought you meant that the booster's bottom blended into the lines of the payload.

The 'orbital' stage would resemble the X-33(SSTO), while the jet booster stage would resemble the X-43(Hypersonic craft propelled by scramjet), but larger than X-33. The X-33 with flat bottom would be on top, while the X-43 with flat top would be below. The flat surfaces will meet together.

http://en.wikipedia.org/wiki/Boeing_X-43
http://en.wikipedia.org/wiki/Lockheed_Martin_X-33

But whether a hypersonic vehicle is capable of taking something as X-33 or even a very lean version without huge performance penalty is still largely unknown. We still have to await the any future scramjet tests, especially if they are capable of piggybacking aerodynamic payloads like a scaled down X-33 for example...

I thought my idea is original but when I read that they are planning to use scramjets as booster stages. They might use the 'glider booster' idea too. :)

 

[Sojourner01]

How about this? http://www.reactionengines.co.uk/sabre.html

They seem to be doing pretty well on this project - though I do wonder why they haven't flown a prototype yet because they've been operational for some time.

 

[FredGarvin]

Where on the website does it say that that engine is operational?

 

[russ_watters]

Eeek - looking at the company website, it looks like the kind of boondoggle that drives me bonkers. They were able to get people to invest in the company and now they are fiddling-around with R&D that may or may not turn into any real product. They are certainly nowhere close to building their engine - the talk only about building and testing a heat exchanger!

 

[joema]

The 'orbital' stage would resemble the X-33(SSTO), while the jet booster stage would resemble the X-43(Hypersonic craft propelled by scramjet), but larger than X-33. The X-33 with flat bottom would be on top, while the X-43 with flat top would be below. The flat surfaces will meet together...I thought my idea is original but when I read that they are planning to use scramjets as booster stages. They might use the 'glider booster' idea too. :)

The concept of a HTHL SSTO with scramjet lower stage has been studied since the 1960s: http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld016.htm

In the mid-60s artist's depictions of a "Siamese" delta-winged TSTO with a scramjet lower stage were published in various popular-level books and magazines. The lower stage had a flat top and the upper stage a flat bottom.

"Winging into space" has always had a romantic appeal. However the cold hard facts are scramjet TSTO or SSTO is incredibly expensive and technically challenging. Indeed, it's been called "getting to space the hard way": http://en.wikipedia.org/wiki/Scramjet

Unlike the casino game of craps, you don't get extra payoff for getting to orbit "the hard way". Rather you want to get there the easiest, simplest way possible.

Given current technology, that's probably some kind of a rocket.

A scramjet TSTO or SSTO would save some money on propellant, as it uses oxygen from the atmosphere. However the liquid oxygen burned by a large rocket booster is almost free. E.g, the gigantic space external tank holds 553,000 liters of LOX, which costs only about $12,000.

 

[gaming_addict]

A scramjet TSTO or SSTO would save some money on propellant, as it uses oxygen from the atmosphere. However the liquid oxygen burned by a large rocket booster is almost free. E.g, the gigantic space external tank holds 553,000 liters of LOX, which costs only about $12,000.

Actually, an SSTO may or may not use air breathing engines. But it was proven even with scramjet equipped types, won't have the payload carrying capacity of multistage rockets.

I'm familiar with the cost of LOX, it's cheap but carrying the weight of LOX will incur a larger amount of fuel burned. The air in the atmosphere is free and doesn't need to be carried around for scramjet.

Anyway, I've realized that if we use TSTO and mix air breathing engines with it. We might get better fuel economy. But due to the complexity of technology used, the operational costs might exceed the cost of fuel used. It might not be practical in the end.

 

[laurelelizabeth]

Oomair, you might be getting misled by some ideas that have been kicking around for atmospheric machines, such as taking off with turbojets and switching to scramjets when supersonic. Those things are not intended to go orbital, and they don't have to carry an oxydizer.

Haha spoken like a true rocket scientist :) that just went over my head, (then proceeded to accelerate towards the ground at -9.8m/s^2)

 

[laurelelizabeth]

What if they made one at a higher altitude, where there would be slightly less air and very slightly less gravity? Or maybe that would be too unpractical if you had to make it in cold conditions...

 

[Danger]

Haha spoken like a true rocket scientist :)

I'm not, but I consider that error a compliment.
Your second post needs clarification. What if they made what at a higher altitude?

 

[russ_watters]

The primary obstacle for a spacecraft to overcome in reaching orbit isn't altitude it is speed.