Gluhareff Pressure Jet

[farmerben]

 

Describe what you could do with these engines....

 

The inventor built helicopters with the engines on the rotor tips and intakes along the blades.

 

My plan is to rail launch out of the Andes at mach 5.  Use ramjets to accelerate across the Atlantic, and detach to land the stage near Kilamanjaro.  Launch a final stage into orbit on oxidizing engines.

 

 

https://en.wikipedia.org/wiki/Gluhareff_Pressure_Jet

 

[Zeiss Ikon]

You're going to be very disappointed.  First, they're approximately as loud as a pulsejet, because they are a form of pulsejet -- resonant pressure waves in the three stage intake act as the "valves", operation is generally similar to a valveless pulsejet like a Thermojet or Lockwood type.  The supersonic nozzle that injects the fuel just acts as the impeller to allow a static start (with correctly tuned intakes), exactly similar to a well tuned Lockwood pulsejet.  The inventor built a helicopter, but hardly anyone has seen it fly -- in SIXTY YEARS.

Second, like any pulsjet, they won't work at supersonic speeds -- front intake pulsejets will either destroy the reed/flapper valve, or lose too much flow due to intake choking; rear intake types (like most valveless designs) will simply die of air starvation.  In neither case is the exhaust supersonic, and an air breathing jet can't exceed its own exhaust velocity in still air.

The Gluhareff jet, like other pulsejets, is impractical for tip-jet helicopters for most of the same reasons ramjets don't work well for this: because specific fuel consumption is too high, it's hard to get both jets ignited simultaneous, and they're too noisy (even compared to a conventional helicopter).  For the same reasons, neither pulsejets nor pressure jets are practical for any other kind of propulsion, unless budget is an extreme driving factor -- because the one advantage valveless pulsejets have is that they're cheap to fabricate (Colin Furze made one by welding two flat pieces of sheet together and using a pressure washer to blow up the resulting part into a tubular shape).  the Gluhareff lacks even that advantage, because it's complex and finicky to build and tune.

[YNM]

Looks just like a pulsejet.

 

Definitely useful for some stunts though.

 

[farmerben]

New engine:

 

A small circular aerospike engine is surrounded by an extra pulse jet nozzle.  The outer nozzle is just far away enough to stay out of direct flame of the aerospike.  Aerospike thrust will keep air moving in the tube so its not a true pulsejet.  Extendable length air intakes can adjust the position of shock cones so intake air has a max compression shock at a precise location just below the truncation of the aerospike.  Hydrocarbon fuel is dumped in at the truncation of the aerospike,  it combusts and exerts extra pressure against the flat of the spike and the outer nozzle.  Functions to some degree at high altitude, because atmospheric oxygen is not required to maintain combustion temp.  

 

... This engine probably stays fixed to the aerospike, no staging.  

[sevenperforce]

14 hours ago, farmerben said:

New engine:

A small circular aerospike engine is surrounded by an extra pulse jet nozzle.  The outer nozzle is just far away enough to stay out of direct flame of the aerospike.  Aerospike thrust will keep air moving in the tube so its not a true pulsejet.  Extendable length air intakes can adjust the position of shock cones so intake air has a max compression shock at a precise location just below the truncation of the aerospike.  Hydrocarbon fuel is dumped in at the truncation of the aerospike,  it combusts and exerts extra pressure against the flat of the spike and the outer nozzle.  Functions to some degree at high altitude, because atmospheric oxygen is not required to maintain combustion temp.  

... This engine probably stays fixed to the aerospike, no staging.  

Congrats, you've invented a partially-airbreathing air-augmented rocket.

[farmerben]

Looks like the Gnom was a solid fuel booster which went from Isp = 180s to Isp =550.  Doesn't say if they make the air fuel rich for afterburner, probably not.

 

NASA thinks they need massive air intakes... they must be doing it wrong.  The key is to use atmospheric oxygen without depending on it to maintain a primary combustion point.

[farmerben]

The saying that fuel is cheap but staging is expensive is less true with a rail launch system.  

The problem with rail launch on Earth is that atmospheric drag kills you.  We need something that can cruise at a steady hyper-sonic speed while gaining elevation.  Save that precious dV for when the atmospheric drag is minimal.   

[Zeiss Ikon]

If you can get something with the aerodynamics of a sounding rocket (i.e. long and slender, with a long pointed nose cone and tiny fins for stability) up to Mach 10 or so, and launch from Colombia at a suitable upward angle, it would climb out of the atmosphere before losing too much speed or burning off the fins, then ought to come close to coasting to the African coast before reentering -- and which time, it's likely to either burn up or break up.  Of course, if you're trying for orbit, you'd start the rocket engine a little before apogee.  Starting from, say, Mach 6 (after aero losses climbing through the atmosphere), a high performance sounding rocket equivalent could just about make a very low, short-term (before it decays) orbit.

Of course, building the rail only makes sense if you plan to launch these on a near-daily basis, which itself only makes sense if you have some pressing need for very short-lived (on the order of weeks, barring electric ramjets to keep them up) low-altitude satellites.

[Gargamel]

11 hours ago, farmerben said:

NASA thinks they need [insert anything aeronautics related]... they must be doing it wrong

If anybody is doing it right, it's probably NASA.    They might be a government organization, but when it comes things that leave the ground, I put my money on them everytime. 

[farmerben]

The USAF has demonstrated that steel tracks and wheels perform just fine at nearly Mach 8.

There is a moment at 12:27 in this video (F III ejection module test) worth watching.  A stubby aircraft detaches from the sled and uses off axis engines to climb.  

A track ramped vertically is better than a horizontal one except when it comes to runway length.  I think we can get a 10 degree angle straight track in the Andes about 30km long capable of accelerating humans to Mach 5.  (conservative estimates, more is possible). 

A tunnel launch system with electric magnetic and gas pressure propulsion is obviously awesome.  But it appears that a completely ordinary railroad on the surface can handle this job, provided it is tuned to precise tolerances.  The capital cost of the latter is fairly trivial.

 

 

 

[wumpus]

5 hours ago, Gargamel said:

If anybody is doing it right, it's probably NASA.    They might be a government organization, but when it comes things that leave the ground, I put my money on them everytime. 

Everytime?  For high visibility projects such as the Shuttle and SLS, many of the decisions come from Congress and outside of NASA which leads to decision that have very little with "doing it right".  Googling "NASA SSTO" gives 60k+ hits.  While many of them have nothing to do with NASA, there are pockets in NASA that simply won't give up on an obviously broken plan.

On the other hand, the converse, that there exists an obvious solution that NASA is ignoring is almost certainly wrong.  I'd go so far as to say the exceptions prove the rule, such as Spacex's example that saving the first stage booster is key (reusing the orbiter might be gravy, but the first stage is key) is *hard* and provably non-obvious.  There was also pushback from NASA on using more advanced gravity tricks than "slingshots" as they wanted to stay "in the big rocket business" (this is harder to justify, and shows that NASA isn't a simple monolithic supply of excellence.  This might also be pushing all those stupid SSTO plans).

[YNM]

2 minutes ago, wumpus said:

Everytime?  For high visibility projects such as the Shuttle and SLS, many of the decisions come from Congress and outside of NASA which leads to decision that have very little with "doing it right".  Googling "NASA SSTO" gives 60k+ hits.

Well, better than a man sitting in front of a terminal sifting through stuff that he sees interesting. And with a copy of KSP.

[magnemoe]

27 minutes ago, wumpus said:

Everytime?  For high visibility projects such as the Shuttle and SLS, many of the decisions come from Congress and outside of NASA which leads to decision that have very little with "doing it right".  Googling "NASA SSTO" gives 60k+ hits.  While many of them have nothing to do with NASA, there are pockets in NASA that simply won't give up on an obviously broken plan.

On the other hand, the converse, that there exists an obvious solution that NASA is ignoring is almost certainly wrong.  I'd go so far as to say the exceptions prove the rule, such as Spacex's example that saving the first stage booster is key (reusing the orbiter might be gravy, but the first stage is key) is *hard* and provably non-obvious.  There was also pushback from NASA on using more advanced gravity tricks than "slingshots" as they wanted to stay "in the big rocket business" (this is harder to justify, and shows that NASA isn't a simple monolithic supply of excellence.  This might also be pushing all those stupid SSTO plans).

Falcon 9 solution is obvious in hindsight and has lots of benefits, an emergency reserve if you get problems like loosing an engine and get to low twr you can use the return fuel to save payload. An option to launch discardable if you need an oversize payload.

The Darpa plan with an winged first stage on the other hand is pretty obvious and has been disused a lot even back in the 50s, back then it would be manned. 
More expensive but its no reason why it should not work. 

SSTO on the other hand is not practical with rocket engines. 

[wumpus]

2 minutes ago, magnemoe said:

Falcon 9 solution is obvious in hindsight and has lots of benefits, an emergency reserve if you get problems like loosing an engine and get to low twr you can use the return fuel to save payload. An option to launch discardable if you need an oversize payload.

The Darpa plan with an winged first stage on the other hand is pretty obvious and has been disused a lot even back in the 50s, back then it would be manned. 
More expensive but its no reason why it should not work. 

SSTO on the other hand is not practical with rocket engines. 

Early shuttle plans assumed landing the primary booster as a Shuttle itself, but this still has a ton of problems involving mounting (and compounds all the shuttle problems of side mounts with multiple side mounts) and staging.  Had spacex tried to recover the booster (starting with parachutes) even in the 1990s, I'd be surprised if they could succeed with a hoverslam.  My point is that typically where NASA appears "wrong", it is typically merely that such a plan is risky and likely exorbitantly expensive if done on NASA cost schedules.  It took 4 landing failures and 4 more "no attempts" during that time before Spacex finally landed a booster, I'd assume that any NASA plan would be canceled long before such success.  The more I look at all the constraints the Shuttle had to fulfill, the more I think it was a miracle of engineering to cover all those points.  I really don't think a "flyable first stage" would have worked as well as the end result (assuming all the rest of the requirements still need to be met).

The other example (fancy gravity tricks) showed NASA being wrong in much the same ways the "NASA is ignoring my brilliant plan that works in KSP" conspiracy theorists insist it is wrong: sometimes it happens, but don't expect to come up with many more examples.

[Gargamel]

17 hours ago, wumpus said:

Everytime?

OK, not everytime.   But the vast majority of the time.  Anything aero related, I'll go with NASA until proven otherwise.