Alternate Nuke Pusher Plate Shapes?

[sevenperforce]

1 hour ago, Spacescifi said:

Twin bell shaped nozzles at the rear, capable of thrust vectoring by pivoting up or down, which also allows for pitch and roll in atmosphere only using twin main engines.

Also, use air intakes and a ramjet to use when the rocket gets the ship up to speed, so it can fly for free almost flying around.

Intake design is nontrivial. Unlike in KSP, you can't just slap an intake on the front and expect the air to get through to the back. The air needs a flow-through path. Moreover, at high-supersonic speeds, you need forebody compression. Finally, you can't balance the engines in the middle of the craft like Skylon or the exhaust will torch the back end of your ship. The intake is going to need to be integrated into the shape of the overall ship.

1 hour ago, Spacescifi said:

Getting to orbit definitely will require propellant though.

Well yes.

Even cruising around will require propellant. You need a way to add energy to the air -- more energy than it already has, mind you, which is A LOT at hypersonic speeds.

Your best bet, presuming total antimatter confinement, is to use a dense cryogenic propellant that does double duty as open-cycle coolant and working mass. Pump the propellant around the combustion chamber, warming it, and then pump it into the chamber along with a small amount of antimatter. It annihilates and does what rocket exhaust does. Make sure it's throttleable. Then you can use this engine on the low-throttle setting to spray superheated exhaust into the airstream, which will heat it up and give you tons of thrust. Once out of the atmosphere, throttle up and use it in pure-rocket mode.

[Spacescifi]

42 minutes ago, sevenperforce said:

Intake design is nontrivial. Unlike in KSP, you can't just slap an intake on the front and expect the air to get through to the back. The air needs a flow-through path. Moreover, at high-supersonic speeds, you need forebody compression. Finally, you can't balance the engines in the middle of the craft like Skylon or the exhaust will torch the back end of your ship. The intake is going to need to be integrated into the shape of the overall.

 

Indeed... too bad KSP does not mod for that... unless it has been done.

 

The intake design is actually a complex subject.

At first I was thinking to just do this:

 

Yet then I read this: This design works fine while traveling at subsonic speed, go supersonic and you flameout, which I presume (I am guessing here) means the rushing air literally blows out the fire of your exhaust and you stall and fall until you go subsonic sgain. If your engine still works at all.

Therefore the solution was shock cones, which make the air subsonic even while going supersonic.

The reason why fighters look like this nowadays?

 

They like to put radar equipment in the nose.

 

Now realistically, to cut down on drag it would be wise to put a shockcone for the nose of my ship, letting the intake run the ship's length until it reaches the engines at the back.

 

So crew and cargo and what not will be around surround the intake line, which is like the hollow spine of the ship.

 

Afterall I have more places to stick radar than the tiny fighter does.

Edited March 25, 2020 by Spacescifi

[sevenperforce]

20 hours ago, Spacescifi said:

Now realistically, to cut down on drag it would be wise to put a shockcone for the nose of my ship, letting the intake run the ship's length until it reaches the engines at the back.

 

So crew and cargo and what not will be around surround the intake line, which is like the hollow spine of the ship.

 

Afterall I have more places to stick radar than the tiny fighter does.

Yeah,, there is a very good possibility that in order to make it work, you'd need to basically make your entire ship the intake. Consider Bucknell's NTTR SSTO, where the entire forebody provides compression:

Also the old LACES (liquid air cycle) design:

Or the X-30 Aerospaceplane:

Here's one where the conical forebody compression is really obvious:

There's another airbreathing SSTO design that used a concave conical forebody and slush hydrogen with payload bay at the rear but I can't find a picture.

One thing for you to keep in mind is that if you're using antimatter, your available dry mass is much higher than these designs, and so you can afford to play around with the physical structure a little -- so you could have a saucer shape with the intakes on the sides, for example.

[Spacescifi]

4 hours ago, sevenperforce said:

 

One thing for you to keep in mind is that if you're using antimatter, your available dry mass is much higher than these designs, and so you can afford to play around with the physical structure a little -- so you could have a saucer shape with the intakes on the sides, for example.

 

Even so the ship is still going to have pointy shock cones sticking out of it, and trying to put nacelles on wings is a bad idea due to shear wind force ripping them off.

 

Honestly... I think to make ANY shape fly we need a type of field control to suck enough air into the engine that the mass flow rate is on par with chemical rocketry.

Not possible I know, but it may be via EM shenanigans or something else one day.

This won't be a NTTR per se, it would need to be something more, as mere fans probably cannoy handle that.

Shock cone still might come in handy. I dunno.

Nonethless, if one really could suck and blow out that much air, anything nearby overhead would get sucked toward the engine.

Think vacuum cleaner on steroids.

The thrust would be dramatic to say the least... rocket like, only with air, likely a plume effect due to compression.

Edited March 26, 2020 by Spacescifi

[sevenperforce]

2 hours ago, Spacescifi said:

Honestly... I think to make ANY shape fly we need a type of field control to suck enough air into the engine that the mass flow rate is on par with chemical rocketry.

Not possible I know, but it may be via EM shenanigans or something else one day.

This won't be a NTTR per se, it would need to be something more, as mere fans probably cannoy handle that.

In order to "suck in" air, you need to lower pressure at your inlet. You can do that with a big-ass turbofan/turbocompressor, or you can use the Coanda effect or laminar flow.

The important thing is that you only need that high mass flow for a very brief period of time. Once you have velocity, the ram effect will do compression for you. So if you have an engine design that can vastly boost thrust for a short period of time without increased dry mass (maybe with lower specific impulse), you just boost hard during the first 30-60 seconds of flight and then you're good.

2 hours ago, Spacescifi said:

Shock cone still might come in handy. I dunno.

You need the entire forebody of the spaceship to act as a shock cone intake for forebody compression.

[Spacescifi]

56 minutes ago, sevenperforce said:

In order to "suck in" air, you need to lower pressure at your inlet. You can do that with a big-ass turbofan/turbocompressor, or you can use the Coanda effect or laminar flow.

 

There is also magnetohydrodynamics.

Ion-propulsion within the atmopshere essentially, plus other ways too.

Not sure if it is the same principle (doubt it), but there are a variety of ways to fly big stuff...  really good MHD will unlock flight in ways that should exceed mechanical turbines.

 

This is weak... but we should get better later on.

http://news.mit.edu/2018/first-ionic-wind-plane-no-moving-parts-1121

https://www.google.com/amp/s/www.theverge.com/platform/amp/2013/4/3/4178708/ionic-thrusters-more-efficient-than-jet-engines-says-MIT-study

Once we scale it up... fun times.

 

Just need power on scifi scales.

Which I have... in scifi.

 

Edited March 27, 2020 by Spacescifi

[kerbiloid]

4 hours ago, Spacescifi said:

http://news.mit.edu/2018/first-ionic-wind-plane-no-moving-parts-1121

A plane with antimatter-powered ion engines and a pusher-plate kick-starter. That's the way I like!

[sevenperforce]

13 hours ago, Spacescifi said:

There is also magnetohydrodynamics.

Ion-propulsion within the atmopshere essentially, plus other ways too.

Not sure if it is the same principle (doubt it), but there are a variety of ways to fly big stuff...  really good MHD will unlock flight in ways that should exceed mechanical turbines.

 

This is weak... but we should get better later on.

http://news.mit.edu/2018/first-ionic-wind-plane-no-moving-parts-1121

https://www.google.com/amp/s/www.theverge.com/platform/amp/2013/4/3/4178708/ionic-thrusters-more-efficient-than-jet-engines-says-MIT-study

Once we scale it up... fun times

With MHD you are still limited by intake area.

It's always going to be better to just use an initial propellant dump to get up to speed. Either that or a rolling start.

[Spacescifi]

10 hours ago, sevenperforce said:

With MHD you are still limited by intake area.

It's always going to be better to just use an initial propellant dump to get up to speed. Either that or a rolling start.

 

Well... that narrows things down quite a bit... does'nt it?

 

Instead of a plethora of scifi SSTO shapes like this...

this...

 

and this,

 

we get something that actually is designed to be an SSTO rather than look like a scifi derivative trope.

 

This:

 

Only with a cone that was sharper and more oblong and with a more convex bottom.

 

That is the optimal SSTO shape with a shock cone intake.

Thank you for helping me find it.

Edited March 28, 2020 by Spacescifi

[farmerben]

Ok question time.  A ramjet and a scramjet constrict airflow to create subsonic zones allowing fuel to mix with air and combustion to occur.  Correct?

A bypass duct compresses air and dumps heat into it through a radiator or duct.  Correct?  Compression is necessary to create a work cycle, but subsonic compression is not required because we are not mixing two fluids to ignite them.  

 

So what do you call an engine that uses intake air at supersonic speeds (with very little compression), and dumps heat into the airflow using supersonic nozzles of another gas?

I think this design gives up a well defined ignition and combustion region.   But still creates power, with possibly far less drag.  

[sevenperforce]

17 minutes ago, farmerben said:

Ok question time.  A ramjet and a scramjet constrict airflow to create subsonic zones allowing fuel to mix with air and combustion to occur.  Correct?

A bypass duct compresses air and dumps heat into it through a radiator or duct.  Correct?  Compression is necessary to create a work cycle, but subsonic compression is not required because we are not mixing two fluids to ignite them.  

So what do you call an engine that uses intake air at supersonic speeds (with very little compression), and dumps heat into the airflow using supersonic nozzles of another gas?

I think this design gives up a well defined ignition and combustion region.   But still creates power, with possibly far less drag.  

You are describing what is colloquially described as a scramrocket or more properly a supersonic-bypass ejector rocket.

Minor correction: a scramjet constricts airflow, but not enough to cause a normal shock which renders the flow subsonic. The combustion takes place within the supersonic airflow -- hence "Supersonic Combusting Ramjet" or SCRamjet. 

On 3/27/2020 at 8:29 PM, Spacescifi said:

we get something that actually is designed to be an SSTO rather than look like a scifi derivative trope.

This:

Only with a cone that was sharper and more oblong and with a more convex bottom.

That is the optimal SSTO shape with a shock cone intake.

Thank you for helping me find it.

This is not the image I was looking for before, but I love this one:

 

[sevenperforce]

55 minutes ago, farmerben said:

A ramjet and a scramjet constrict airflow to create subsonic zones allowing fuel to mix with air and combustion to occur.  Correct?

Helpful terminology...

• Jet. Any engine which uses the expansion of a working fluid from a nozzle to directly produce thrust via Newton's Third Law.
• Combustion Pulsejet. A jet engine which uses a simple inlet to mix air with fuel to create repeated explosions for pulses of thrust.
• Combustion Turbojet. A jet engine which uses an axial turbocompressor to compress and mix air with fuel to burn and create continuous thrust.
• Turboprop. A turbojet engine which gears its axial turbocompressor to a propeller to create secondary thrust at low-subsonic airspeeds.
• Bypass Turbofan. A turbojet engine which gears its axial turbocompressor to a large ducted fan to create secondary thrust at high subsonic airspeeds.
• Combustion Ramjet. A jet engine which uses shock cone intake geometry to trade inlet air's speed for compression to combust at subsonic speeds.
• Supersonic Combustion Ramjet or scramjet. A ramjet which uses a wider shock cone intake geometry to allow compressed combustion at supersonic speeds.
• Ejector jet or ducted rocket. A rocket with an air inlet and duct. Atmospheric air is entrained by the exhaust's low static pressure, then compressed and heated by its high dynamic pressure to expand against the duct as additional working fluid.
• Turborocket. An ejector jet which uses an axial turbocompressor to compress air at the inlet before mixing with the rocket exhaust.
• Ramrocket. An ejector jet with shock cone intake geometry to compress the air to subsonic flow speed before mixing with the rocket exhaust.
• Scramrocket. An ejector jet with wider shock cone intake geometry that compresses the air, but not so far that it reaches subsonic flow speed.
• Rocket-Based Combined-Cycle (RBCC) Engine. Any engine which operates in different modes (ejector jet, ramjet, turborocket, etc.) at different speeds and altitudes.

Also, I love this design:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.526.7376&rep=rep1&type=pdf

Uses jelled aluminum in liquid methane to create a high-density, high-energy propellant. Sled-launched RBCC SSTO that operates as an ejector jet, a ramjet, a scramjet, a scramrocket, and a pure rocket.

Edited March 31, 2020 by sevenperforce

[Spacescifi]

23 hours ago, sevenperforce said:

Helpful terminology...

• Jet. Any engine which uses the expansion of a working fluid from a nozzle to directly produce thrust via Newton's Third Law.
• Combustion Pulsejet. A jet engine which uses a simple inlet to mix air with fuel to create repeated explosions for pulses of thrust.
• Combustion Turbojet. A jet engine which uses an axial turbocompressor to compress and mix air with fuel to burn and create continuous thrust.
• Turboprop. A turbojet engine which gears its axial turbocompressor to a propeller to create secondary thrust at low-subsonic airspeeds.
• Bypass Turbofan. A turbojet engine which gears its axial turbocompressor to a large ducted fan to create secondary thrust at high subsonic airspeeds.
• Combustion Ramjet. A jet engine which uses shock cone intake geometry to trade inlet air's speed for compression to combust at subsonic speeds.
• Supersonic Combustion Ramjet or scramjet. A ramjet which uses a wider shock cone intake geometry to allow compressed combustion at supersonic speeds.
• Ejector jet or ducted rocket. A rocket with an air inlet and duct. Atmospheric air is entrained by the exhaust's low static pressure, then compressed and heated by its high dynamic pressure to expand against the duct as additional working fluid.
• Turborocket. An ejector jet which uses an axial turbocompressor to compress air at the inlet before mixing with the rocket exhaust.
• Ramrocket. An ejector jet with shock cone intake geometry to compress the air to subsonic flow speed before mixing with the rocket exhaust.
• Scramrocket. An ejector jet with wider shock cone intake geometry that compresses the air, but not so far that it reaches subsonic flow speed.
• Rocket-Based Combined-Cycle (RBCC) Engine. Any engine which operates in different modes (ejector jet, ramjet, turborocket, etc.) at different speeds and altitudes.

Also, I love this design:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.526.7376&rep=rep1&type=pdf

Uses jelled aluminum in liquid methane to create a high-density, high-energy propellant. Sled-launched RBCC SSTO that operates as an ejector jet, a ramjet, a scramjet, a scramrocket, and a pure rocket.

 

I read some of the PDF... fascinating.

 

Just curious, what design changes would you make to the craft if Gov let you stick in as many nuclear reactors into it as you like but addes one requirement:

The SSTO must have a crew capacity of 15 and a cargo payliad capacity of 40 tons.

Right away I am thinking the craft woud need to be bigger and heavier.

 

Also, if you take the original design and intergrate nuclear thermal does that enhance psrformance at all?

 

[sevenperforce]

1 hour ago, Spacescifi said:

Just curious, what design changes would you make to the craft if Gov let you stick in as many nuclear reactors into it as you like but addes one requirement:

The SSTO must have a crew capacity of 15 and a cargo payliad capacity of 40 tons.

Right away I am thinking the craft woud need to be bigger and heavier.

Rail launch is not great for human cargo. As a rule, an airbreathing lifting-body SSTO is a poor choice for crew to begin with because there's no good abort mode when you're pointed face-first into what is nearly a re-entry environment.

The original design uses high-energy-density fuel, with liquid methane and aluminum gellant. If you're swapping in nukes you no longer need high energy density. What I'd do, if the government gave me a bunch of nukes to roll in, would be to replace the LOX tanks with water tanks and feed the nuclear-thermal engine with a mixture of water and regular liquid methane in varying mixture ratio so I could get high thrust (with water) at the beginning and high specific impulse (with methane) at the end, varying as needed. You'd need multiple injectors because of temperature issues but otherwise it works very well.

And yes, much bigger. More like the shuttle layout -- maybe with the crew in the nose having canards and being an independent re-entry vehicle.

[Spacescifi]

22 hours ago, sevenperforce said:

Rail launch is not great for human cargo. As a rule, an airbreathing lifting-body SSTO is a poor choice for crew to begin with because there's no good abort mode when you're pointed face-first into what is nearly a re-entry environment.

The original design uses high-energy-density fuel, with liquid methane and aluminum gellant. If you're swapping in nukes you no longer need high energy density. What I'd do, if the government gave me a bunch of nukes to roll in, would be to replace the LOX tanks with water tanks and feed the nuclear-thermal engine with a mixture of water and regular liquid methane in varying mixture ratio so I could get high thrust (with water) at the beginning and high specific impulse (with methane) at the end, varying as needed. You'd need multiple injectors because of temperature issues but otherwise it works very well.

And yes, much bigger. More like the shuttle layout -- maybe with the crew in the nose having canards and being an independent re-entry vehicle.

 

I see.

So the only way using IRL known tech to make large cargo/passenger SSTO will be to do it in pairs.

Ship one gets to orbit. Ship two is full of propellant and refuels ship one for a future landing somewhere.

The more full tank ships you have the more landings and launches you can do. There will or should always be tankers on the ground and in orbit for refueling to refuel the passenger spaceship as needed.

This also means that fuel tankers are... well... disposable.

So in a way... we never stopped staging. It's just with fuel tank ships.

 

Right now I see a proper SSTO as a hybrid of pusher plate and airbreathing turborocket technology.

 

An initial propellant lift off and then the bombs do the rest. Refuel with tanker in orbit go (or warp scifi style) where you wanns go and rinse and repeat.

 

EDIT: For maximum reuse I suggest a few tankers with ISRU machinery.

Essentially SSTO's that can go down, make fuel, reload a grounded ship, reload itself, and get back to orbit.

 

A tall order? Yeah... buy it is also necessary.

Edited April 2, 2020 by Spacescifi

[farmerben]

How about a pusher plate combined with an air hockey table.  

Pop out sprinklers cover the pusher plate and all its' pores with soap and oil.

Then the air hockey system bubbles out hydrogen gas.   So 1mm of oily soap is like 10 x 1cm bubbles, when you nuke it.  

 

Also make the plate resemble the head of a nail.  The more massive the spine attached to the pusher plate the less jerky the whole thing is.  And the entire spine could be a giant ferromagnet.  Tubular coils supporting toroidal payload structures would resist relative motion, without being subject to parts wear as would springs and pneumatic shocks.    

 

Edited April 2, 2020 by farmerben