Hybrid propulsion system Q&A

[Robotbeat]

It's all the basic physics of the concept. Hypergols don't need an igniter. If they are in contact with each other in the combustion chamber, your engine is firing, simple as that. For a pressure-fed design (i.e. no turbine to spin-up...  no pump on any of the abort designs we've seen for CCDev, of course), it's very simple and can be very fast.

Is Falcon less reliable or bad from a physics perspective because it is not hypergolic, needs an ignitor and not pressure fed? 

Bad? No, just different. Less reliable from an ignition standpoint? Yes. And also less reliable than a pressure fed because it has a turbopump and other complicated plumbing? Yes, as you saw on the recent launch scrub/abort.

Merlins would make poor abort motors. Apparently they take the better part of a second to get to full thrust.

So, it's just different.  Different does not have to mean bad.  You are seemingly fixated on aborts.  The engines themselves are more than abort motors.  If they had engines/motors dedicated only to aborts I have the feeling you would be suggesting it is waste and cost driver. 
...

Putting words in my mouth. It all depends on the details, doesn't it? I just don't think hybrids are a very good fit for aborts. I don't think they're terribly good for orbital maneuvering thrusters, either. But that's less important, since you can make the argument that operational cost reduction is more important (I'd still say ethanol may be better... like the old Shuttle concept). I suppose ignition reliability is also pretty important for things like deorbit burns and the like.

As far as thrust traces... I've never built and test-fired two identical-class abort thrusters, one hybrid and one hypergolic bipropellant. Fact. But I fail to see why that means we can't talk about it conceptually. Can you explain why (physically) a hybrid can be expected to be as fast as a hypergolic bipropellant pressure-fed abort motor (what Boeing and SpaceX are using)?

[Chris Bergin]

fsfsd

[Jorge]

fsfsd

asdfasdfasdf

Copy and concur.

[yg1968]

But anyway, I am not going to be bullied away from my opinion of the technical merits of the situation by you claiming I'm denigrating some engineers by having such an opinion! But this is getting far off topic, now. I think this is essentially an update thread (if not explicitly), and this is a conversation more appropriate to a side thread.

I am not "bullying you away from your opinion".  Instead I am asking for substantiated facts and how this "opinion" holds any merit when it is based on subjecture and the central argument is that it is not "proven", something I believe your post history would not support with respect to SpaceX.  Therefore I am simply looking for the apples-to-apples comparison.

So I will end it with this.

1.  Have you ever designed or worked on spacecraft and/or their systems, including design cycles and operations?

2.  Have you ever worked on hybrid systems?

3.  Have you ever worked on hypergolic systems?

And, just so you know, the answer for me is yes to all 3. 

Welcome back OV-106...

[QuantumG]

Dear industry experts. If your argument is "I'm an expert, so I know" then you lose the argument. If you know, then you should have no problem convincing the guy who doesn't. If you can't, then you don't know.

Appeals to authority, especially your own authority, are intellectually lazy. Chastise yourself and make a convincing argument.

[Jason1701]

But anyway, I am not going to be bullied away from my opinion of the technical merits of the situation by you claiming I'm denigrating some engineers by having such an opinion! But this is getting far off topic, now. I think this is essentially an update thread (if not explicitly), and this is a conversation more appropriate to a side thread.

I am not "bullying you away from your opinion".  Instead I am asking for substantiated facts and how this "opinion" holds any merit when it is based on subjecture and the central argument is that it is not "proven", something I believe your post history would not support with respect to SpaceX.  Therefore I am simply looking for the apples-to-apples comparison.

So I will end it with this.

1.  Have you ever designed or worked on spacecraft and/or their systems, including design cycles and operations?

2.  Have you ever worked on hybrid systems?

3.  Have you ever worked on hypergolic systems?

And, just so you know, the answer for me is yes to all 3. 

Welcome back OV-106...

I thought the exact same thing

[gin455res]

Interesting talk about hybrids, viscosity of the melting surface and it consequences on regression and the use of nytrox.

!

[gin455res]

oh, and the use of paraffin/aluminium fuels

[Vahe231991]

We know that the unbuilt X-30/NASP, British HOTOL, Sanger II, and Tu-2000 were intended to use a hybrid scramjet/rocket propulsion system, with the scramjet to be used for most of the flight to orbit and the rocket to be activated for the final kick into orbit. However, what would be the advantages and disadvantages of the hybrid scramjet/rocket propulsion system for a spaceplane compared to the hybrid propellant rocket propulsion system pioneered for SpaceShipOne and now being used for SpaceShipTwo and SpaceShipThree?

[edzieba]

We know that the unbuilt X-30/NASP, British HOTOL, Sanger II, and Tu-2000 were intended to use a hybrid scramjet/rocket propulsion system, with the scramjet to be used for most of the flight to orbit and the rocket to be activated for the final kick into orbit. However, what would be the advantages and disadvantages of the hybrid scramjet/rocket propulsion system for a spaceplane compared to the hybrid propellant rocket propulsion system pioneered for SpaceShipOne and now being used for SpaceShipTwo and SpaceShipThree?

Apart from having the word 'hybrid' in the name, those two concepts are unrelated.

'Hybrid rockets' are rocket engines where you mix a solid fuel and a liquid oxidiser (or theoretically a liquid fuel and a solid oxidiser).

Hybrid systems are vehicles where you have multiple different types of propulsion (e.g. rocket and jet turbine, ramjet and scramjet, jet turbine and propeller, etc) on the same vehicle.

[Vahe231991]

We know that the unbuilt X-30/NASP, British HOTOL, Sanger II, and Tu-2000 were intended to use a hybrid scramjet/rocket propulsion system, with the scramjet to be used for most of the flight to orbit and the rocket to be activated for the final kick into orbit. However, what would be the advantages and disadvantages of the hybrid scramjet/rocket propulsion system for a spaceplane compared to the hybrid propellant rocket propulsion system pioneered for SpaceShipOne and now being used for SpaceShipTwo and SpaceShipThree?

'Hybrid rockets' are rocket engines where you mix a solid fuel and a liquid oxidiser (or theoretically a liquid fuel and a solid oxidiser).

Hybrid systems are vehicles where you have multiple different types of propulsion (e.g. rocket and jet turbine, ramjet and scramjet, jet turbine and propeller, etc) on the same vehicle.

Does a hybrid scramjet/rocket propulsion system for a single-stage-to-orbit aerospaceplane design have a higher specific impulse than a hybrid propellant rocket propulsion system?

[Redclaws]

We know that the unbuilt X-30/NASP, British HOTOL, Sanger II, and Tu-2000 were intended to use a hybrid scramjet/rocket propulsion system, with the scramjet to be used for most of the flight to orbit and the rocket to be activated for the final kick into orbit. However, what would be the advantages and disadvantages of the hybrid scramjet/rocket propulsion system for a spaceplane compared to the hybrid propellant rocket propulsion system pioneered for SpaceShipOne and now being used for SpaceShipTwo and SpaceShipThree?

'Hybrid rockets' are rocket engines where you mix a solid fuel and a liquid oxidiser (or theoretically a liquid fuel and a solid oxidiser).

Hybrid systems are vehicles where you have multiple different types of propulsion (e.g. rocket and jet turbine, ramjet and scramjet, jet turbine and propeller, etc) on the same vehicle.

Does a hybrid scramjet/rocket propulsion system for a single-stage-to-orbit aerospaceplane design have a higher specific impulse than a hybrid propellant rocket propulsion system?

Hugely.  The ISP on air breathing engines of any kind is extremely high because they don’t carry their own reaction mass.  Ie they can push/pull their way using the medium they’re traveling in rather than relying on purely equal and opposite reactions by throwing mass out the back like rockets.

[Jim]

We know that the unbuilt X-30/NASP, British HOTOL, Sanger II, and Tu-2000 were intended to use a hybrid scramjet/rocket propulsion system, with the scramjet to be used for most of the flight to orbit and the rocket to be activated for the final kick into orbit. However, what would be the advantages and disadvantages of the hybrid scramjet/rocket propulsion system for a spaceplane compared to the hybrid propellant rocket propulsion system pioneered for SpaceShipOne and now being used for SpaceShipTwo and SpaceShipThree?

'Hybrid rockets' are rocket engines where you mix a solid fuel and a liquid oxidiser (or theoretically a liquid fuel and a solid oxidiser).

Hybrid systems are vehicles where you have multiple different types of propulsion (e.g. rocket and jet turbine, ramjet and scramjet, jet turbine and propeller, etc) on the same vehicle.

Does a hybrid scramjet/rocket propulsion system for a single-stage-to-orbit aerospaceplane design have a higher specific impulse than a hybrid propellant rocket propulsion system?

Other than pure solid rocket motors, anything else has higher ISP than hybrid motors.

Also, SSTO aerospace plane has nothing to do with the matter.