What's Your Definition of "Rocket" ?

[Geschosskopf]

My definition is that a rocket is a big bag full of money that you set on fire and catapult into the faces of the uncaring gods in hopes of smacking them in the nose.  Kinda like in the video linked  HERE (although you have to jump to about 1:45 for the relevant part).

Edited January 6, 2018 by Geschosskopf

[Ty Tan Tu]

I was going to say a self contained propulsion system that does not depend on outside resources, but any reference to Monty Python gets a rec from me.

I have been thinking that with the recent advances in steroids, we should revisit the Ralph Kramden delivery system , but it seems like vaporware. It i always 'one of the days, one of the days'.

 

[Starman4308]

My instinctive reaction is "something with a combustion chamber and a nozzle". I suppose that excludes some things like cold-gas thrusters that are, arguably, rockets.

[Tony805]

Maybe "Something can fly without wings and it can work on its own, no need to work rely on something outside like air."

[Jack5.exe]

a cylinder that flys with possible other cylinders

[Cadet_BNSF]

A device which uses pressure differentials to create a force that can propel an object, either through space or an atmosphere.

Very useful items, particularly when you want to get to space.

Or when you want to do this

 

[LordFerret]

2 hours ago, Ty Tan Tu said:

...

[ARS]

Purposely trying to contain and control a series of reaction that burns violently using chemical mixture inside a tube of steel and metal casing while trying to keep the resultant product pointed at the ground using a series of expensive equipment, needlessly complicated precautions and other shenanigans to prevent it goes kaboom

[John FX]

A slow bomb.

[NSEP]

A controlled explosive device mainly used in recreational purposes (fireworks), military (missles) and spaceflight (launch vehicles)

[Just Jim]

After playing this game way too long...

Rocket: Something that explodes more or less up off a launch pad
Spaceplane: Something that explodes more or less forward down a runway...

Edited January 6, 2018 by Just Jim

[KSK]

A happyfun tube of boom. Comes in various sizes, sometimes with a car on top.

[Rocket In My Pocket]

It ain't no rocket; if it don't fit in my pocket.

[Jeb, The Lonely Kerbonaut]

A thing with one (or more) giant metal cylinder with special fuel, with an complex engine that burns the fuel, making this thing goes up. Sometimes they have some metal cylinders with another special fuel and an engine that burns the fuel without stop (also called SRBs). Is very aerodynamic, and generally transports satellites, probes, station modules and supplies to space stations, rovers (cars, sometimes) and humans to space, the Moon, Mars and beyond.

Edited January 6, 2018 by Jeb, The Lonely Kerbonaut

[Starman4308]

Some good stuff in here, though it can be awfully hard to define a rocket.

13 hours ago, Tony805 said:

Maybe "Something can fly without wings and it can work on its own, no need to work rely on something outside like air."

Solar and/or laser sails would count under this definition.

12 hours ago, Cadet_BNSF said:

A device which uses pressure differentials to create a force that can propel an object, either through space or an atmosphere.

Very useful items, particularly when you want to get to space.

A bomb would count under this definition. Granted, if you added the modifiers "sustained" and "directed", that closes that loophole.

9 hours ago, ARS said:

Purposely trying to contain and control a series of reaction that burns violently using chemical mixture inside a tube of steel and metal casing while trying to keep the resultant product pointed at the ground using a series of expensive equipment, needlessly complicated precautions and other shenanigans to prevent it goes kaboom

Nuclear thermal rockets!

Also: https://www.rocketlabusa.com/electron/ ; even orbital launch vehicles don't have to be made out of metal (nevermind Estes rockets!).

6 hours ago, John FX said:

A slow bomb.

Stick a parachute on the bomb?

Overall, the best I can think of (poaching heavily from @Cadet_BNSF ) is a device using sustained*, directed pressure differentials to propel onboard reaction mass in a consistent direction as means of propulsion. While some varieties such as air-augmented rockets can benefit from external reaction mass, the rocket must be capable of operating in vacuum, with purely onboard reaction mass.

*Can be either fully sustained or pulsed. The second is a feature of Project "Let's go to space on nuclear bombs!"

 

This definition should include:

"Regular" rocket engines.

Pulsed rocket engines (such as Project Orion).

Various flavors of air-augmented rocket, so long as they are capable of vacuum operation.

Nuclear thermal engines.

Possibly ablative laser propulsion.

Guns used as a means of propulsion.

 

This definition should exclude:

Strictly air-breathing engines such as jet and piston engines.

Solar sails.

Pure photon drives.

Guns used as guns.

Non-gas-based mass accelerators such as railguns and trebuchets.

 

EDIT: And now I've realized the definition excludes ion engines, since for those, the method of acceleration is generally based on the electromagnetic force, not a pressure differential.

Edited January 6, 2018 by Starman4308
Defining rockets is a tricky and difficult business

[FrostedShoe]

6 hours ago, John FX said:

A slow bomb.

I would have thought a rocket was a fast bomb as a bomb just falls under gravity?

[Joseph Kerman]

A rocket is a torpedo-shaped object that can lift itself, some fuel, and payload off the ground an into space. Those Mammoth engine SSTO tugs aren't rockets to me, but is one from a simple perspective.

[fourfa]

I found this kind of interesting:

One of the more surprising words to come from Italian is rocket. In Italian, ‘rocca’ was originally the word for the part of a weaver’s loom that held the wool, and the diminutive form of this, ‘rocchetta’, came to be used for a self-propelling cylinder in various mechanical devices. In French, this became ‘roquette’, and the word finally entered English as ‘rocket’ in the 17th century.

[Urus28]

I would say a flying device relying more on its engine thrust than lift to fly.

[Cadet_BNSF]

7 hours ago, Starman4308 said:

EDIT: And now I've realized the definition excludes ion engines, since for those, the method of acceleration is generally based on the electromagnetic force, not a pressure differential

That occurred to me as well. I couldn't come up with a way to include those in my definition, so I left it as is.

 

7 hours ago, Starman4308 said:

a device using sustained*, directed pressure differentials to propel onboard reaction mass in a consistent direction as means of propulsion. While some varieties such as air-augmented rockets can benefit from external reaction mass, the rocket must be capable of operating in vacuum, with purely onboard reaction mass.

However, building off of your extension of my definition, a rocket is a device that, using some sustained or pulsed, on board force such as a pressure differential or electromagnetic field, propels onboard reaction mass in a consistent direction as a means of propulsion. While some varieties such as air-augmented rockets can benefit from external reaction mass, the rocket must be capable of operating in vacuum, with purely onboard reaction mass.

This should include 

chemical rocket engines

Project Orion-esque rockets

Ion engines, i.e. Hall effect thrusters

Ship mounted guns used as drives

Quote

"Alex, how much acceleration does a two-kilo slug travelling at five thousand meters per second give the ship?"

"Enough," Alex replied with a sly grin,"  that we're only supposed to fire it with the main drive on"

"Sounds like a thruster to me," Naomi said, grinning back at him

James S. A. Corey, Cibola Burn, The Expanse

Compressed gas thrusters such as an RCS system

Nuclear thermal engines

VASIMIR type engines

 

Won't include 

Ablative laser systems

Solar sails

mass drivers and the like

orbital rings and space elevators

[Ten Key]

Moved thread to the Lounge, as it is not about KSP and the "science and spaceflight" bits are somewhat tenuous.  

[wumpus]

Does it obey the rocket equation?  Is it spitting out mass&velocity in one direction and getting momentum in the other?  If so it is a rocket.

Note that this gets rather fuzzy where the line has to be drawn between:

High bypass turbofans [almost certainly not rockets]
Classic turbojets (what is typically used for supersonic flight) [not quite rockets]
Ramjets/Scramjets [getting to being a rocket]
SABRE [probably a rocket, but maybe not for models that can't fire in vacuum]
Air-augmented rocket [almost always considered a rocket]
Classical rockets (supply their own oxidizer) [always considered a rocket]

 

[John FX]

On 06/01/2018 at 4:35 PM, FrostedShoe said:

I would have thought a rocket was a fast bomb as a bomb just falls under gravity?

Trust me, bombs are a lot faster than rockets. Rockets explode very slowly. Except for when they turn into actual bombs and explode very quickly.

Even then, they are a lot slower than most bombs.

[cubinator]

An up goer that works in space.

[kerbiloid]

A rocket turns good things into wastes, drops them and runs away from that place as if nobody knows.