For Questions That Don't Merit Their Own Thread

[kerbiloid]

A missile as a purpose, a rocket as a physical principle of propulsion.

[ARS]

45 minutes ago, kerbiloid said:

A missile as a purpose, a rocket as a physical principle of propulsion.

Isn't that applies on every rockets and missiles? I thought the missile definition generally means it's guided, while a rocket is the 'less guided' (or unguided) term. People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

[kerbiloid]

29 minutes ago, ARS said:

Isn't that applies on every rockets and missiles? I thought the missile definition generally means it's guided, while a rocket is the 'less guided' (or unguided) term. People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

As I can get from the English Q&As, the missile is not necessary "guided", but "intentionally aimed at".

Edited December 10, 2021 by kerbiloid

[DDE]

36 minutes ago, ARS said:

Isn't that applies on every rockets and missiles? I thought the missile definition generally means it's guided, while a rocket is the 'less guided' (or unguided) term. People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

Primarily because this was before the rather artificial rocket-missile distinction (in fact, before the adoption of the term "rocket" in certain languages).

[ARS]

49 minutes ago, DDE said:

Primarily because this was before the rather artificial rocket-missile distinction (in fact, before the adoption of the term "rocket" in certain languages).

Ah I see, so that's before the era of guided missiles when people start to distinguish between the guided/ unguided distinction

[magnemoe]

3 hours ago, ARS said:

Isn't that applies on every rockets and missiles? I thought the missile definition generally means it's guided, while a rocket is the 'less guided' (or unguided) term. People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

Think its multiple terms here, an rocket is everything from firework to Saturn 5. 
An missile is an weapon aimed at an target and does not need to be rocket powered, cruise missiles are jet powered, same are some anti ship and some anti air missiles has used ramjets. 

However small rockets like the 70 mm ripple fired from pods on helicopters or ground attack planes are rockets, now if they get upgraded to be smart I think they would still be rockets  

 

[sevenperforce]

4 hours ago, ARS said:

People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

The V-2 was not a cruise missile; the V-2 was the first ballistic missile.

The V-1 was a cruise missile. Cruise missiles are designed to fly on non-ballistic, powered trajectories, usually (but not always) using airbreathing engines. For the V-1, it was a pulsejet engine. It is possible to build an unguided cruise missile, although in practice it isn’t typically done; even the V-1 had a crude guidance system.

A “missile” is anything with a physical target. In the era of seige warfare, the projectiles launched by ballistae and catapults were referred to as missiles. Even rocks and bricks thrown by an angry mob used to be referred to as a “hail of missiles” because a missile was anything thrown, launched, or propelled toward a target.

A rocket, on the other hand, refers to a vehicle with a particular type of propulsion. Technically, a rocket is a subset of reaction engine, where a reaction engine is any engine which produces thrust by the expansion of a fluid from a high-pressure to a low-pressure region. Rockets usually add thermal energy to their working fluid while it is compressed, though they don’t necessarily need to (e.g., cold gas thrusters and water rockets). The term “rocket” is usually used to refer to a reaction engine which contains its working fluid within itself, as distinguished from reaction engines which compress and release ambient fluid (e.g. turbojet, pulsejet, ramjet, or a hydrojet).

So a missile is something with a target; a rocket is something with a particular type of propulsion.

[JoeSchmuckatelli]

6 hours ago, ARS said:

Isn't that applies on every rockets and missiles? I thought the missile definition generally means it's guided, while a rocket is the 'less guided' (or unguided) term. People called the V2 as 'rocket' even though by definition it's a cruise 'missile'

That is correct but only in the context of military weapons.  "Guided Missile" has its own internal or wire/other intput method for the operator or its own programming to adjust flight after launch to hit the target.  Rockets are generally aimed by the firing agency (helicopter, katyusha, etc) and then go, hopefully, where aimed - but once launched don't make intentional changes to adjust for movement or refinement of the target.

In the context of larger systems - like ballistic, orbital or sub-orbital systems, from what I gather the only difference between terminology is the purpose.  "Missiles" are weapons with a purpose of destruction.  "Rockets" are peaceful, scientific or commercial lifters (that can lift defensive or information-gathering military payloads) but don't have the immediate purpose of hostile action or destruction of a target.  That said, there's likely little to differentiate the two; they both have guidance systems - both onboard and ground/satellite based.

EDIT: this is what makes MAD really exciting.  No one knows the purpose of the rocket when launched... 

Edited December 10, 2021 by JoeSchmuckatelli

[JoeSchmuckatelli]

https://www.google.com/amp/s/www.newsweek.com/galaxies-killed-spectacular-violent-external-forces-alma-gas-stripping-virgo-cluster-vertico-1645405%3famp=1

Virgo Cluster does not look like a fun neighborhood. 

Speaking of hostile environments:

https://www.nbcnews.com/science/science-news/massive-planet-10-bigger-jupiter-discovered-orbiting-pair-giant-stars-rcna8085

Edited December 10, 2021 by JoeSchmuckatelli

[kerbiloid]

7 hours ago, JoeSchmuckatelli said:

https://www.google.com/amp/s/www.newsweek.com/galaxies-killed-spectacular-violent-external-forces-alma-gas-stripping-virgo-cluster-vertico-1645405%3famp=1

Out of gas.

Spoiler

 

[JoeSchmuckatelli]

1 hour ago, kerbiloid said:

Out of gas

 

[kerbiloid]

What if the Earth is not actually flat, but just has a close to infinity radius?

How would it affect the spaceflights and science?

[ARS]

54 minutes ago, kerbiloid said:

What if the Earth is not actually flat, but just has a close to infinity radius?

How would it affect the spaceflights and science?

A circle with infinite radius is a line, close to infinity means slightly curved line

Edited December 11, 2021 by ARS

[tater]

"Missile" used to just be a projectile in English.

Slings, bows, and flintlocks all sent "missiles" down range.

In modern use (least in the US), for weapon systems, "missile" implies guidance to me, rockets are unguided.

Rockets are what we think of as rockets for launch vehicles, lol.

English is not rational.

Edited December 12, 2021 by tater

[JoeSchmuckatelli]

For those who want to believe:

https://astronomy.com/news/2021/12/technosignature-from-proxima-centauri--and-why-astronomers-rejected-it

[kerbiloid]

They should concentrate on the most popular internet content, the extraterrestrial Phub and kittens (whatever they call "kitten" among their local lifeforms).

[ARS]

Does this statement correct?

"The solid-fuel rocket provides massive thrust at cheaper price than liquid-fuel rocket, at the cost of its inability to be throttled and turned off once ignited and short operating time. With high thrust to weight ratio, a strap-on solid rocket booster is always a good choice to be added for an extra thrust during the liftoff"

Mainly on this part: "...a strap-on solid rocket booster is always a good choice to be added for an extra thrust..."

Since SRB usually have high TWR (more than enough to lift it's own mass to pretty high altitude before running out of fuel), strapping them on larger rocket seems like a good idea for "free" extra thrust (strictly speaking from physics standpoint, ignoring cost or other mechanical complexity). However, is there any situation (payload profile, weather condition, a certain point in rocket's total mass. In a sensibly-designed rocket of course) that makes adding a strap-on SRB no longer provides any benefit and instead being detrimental to the mission?

[sevenperforce]

14 minutes ago, ARS said:

Since SRB usually have high TWR (more than enough to lift it's own mass to pretty high altitude before running out of fuel), strapping them on larger rocket seems like a good idea for "free" extra thrust (strictly speaking from physics standpoint, ignoring cost or other mechanical complexity). However, is there any situation (payload profile, weather condition, a certain point in rocket's total mass. In a sensibly-designed rocket of course) that makes adding a strap-on SRB no longer provides any benefit and instead being detrimental to the mission?

Well, real-life solid rocket boosters are much more expensive in comparison to liquid alternatives than is suggested in KSP, so that's one big difference.

But it all comes down to design choice. For example, the liftoff TWR of the Falcon family of rockets is already quite high, and so adding SRBs would result in increased complexity, higher stresses at MaxQ, and a higher staging velocity. And since the Falcon family prefers a lower staging velocity to allow recovery of the booster, solids don't make sense.

For vehicles like Atlas V, Delta IV, or Vulcan, all of which use very high staging velocities and have overbuilt cores, solids are a good addition.

[ARS]

4 hours ago, sevenperforce said:

Well, real-life solid rocket boosters are much more expensive in comparison to liquid alternatives than is suggested in KSP

How SRB being more expensive than liquid fuel rockets when SRB is relatively simpler in design? (no kind of complicated plumbing, valves, fuel lines, cryogenic fuel tanks, etc.)

[kerbiloid]

SRB is more complicated in both design and manufacturing.

Because in a liquid rocket you solve the problems by plumbing, valves, fuel lines, while SRB should provide all of that by proper shaping and layering.

(And still need the nozzle part with its equipment.)

Edited December 13, 2021 by kerbiloid

[K^2]

7 hours ago, ARS said:

How SRB being more expensive than liquid fuel rockets when SRB is relatively simpler in design? (no kind of complicated plumbing, valves, fuel lines, cryogenic fuel tanks, etc.)

I think @sevenperforce meant that the gap in cost between SRB and liquid is much smaller IRL than in KSP. Not that solids are necessarily more expensive. I'm pretty sure it's still cheaper to build a solid booster than a liquid one for the same thrust and total impulse. I don't have full confidence, though. Also, if you factor in reusable stages, this balance will easily swing in favor of liquid engines all together. SRB fuel, both the raw materials and the process to make it into boosters, is rather expensive. And there's a lot of that fuel, so it does add up. If it doesn't quite add up to a cost of liquid fuel engine on one launch, it certainly will over multiple.

[sevenperforce]

11 minutes ago, K^2 said:

7 hours ago, ARS said:

How SRB being more expensive than liquid fuel rockets when SRB is relatively simpler in design? (no kind of complicated plumbing, valves, fuel lines, cryogenic fuel tanks, etc.)

I think @sevenperforce meant that the gap in cost between SRB and liquid is much smaller IRL than in KSP. Not that solids are necessarily more expensive. I'm pretty sure it's still cheaper to build a solid booster than a liquid one for the same thrust and total impulse.

Yes, that's what I meant -- solids are more expensive comparatively than you would think from KSP, even though they are still a little cheaper than liquids. They're just not massively cheaper as depicted in KSP.

Solids also have some unpleasant attributes, like the fact that you have to ship them from manufacture to launch site already filled with their propellant. Even though modern solids are very safe from accidental ignition, that's still a LOT of weight to carry around; liquid-fueled rocket stages are comparatively lightweight and so shipping isn't nearly as costly or challenging. 

 

 

[wumpus]

2 hours ago, sevenperforce said:

Yes, that's what I meant -- solids are more expensive comparatively than you would think from KSP, even though they are still a little cheaper than liquids. They're just not massively cheaper as depicted in KSP.

Solids also have some unpleasant attributes, like the fact that you have to ship them from manufacture to launch site already filled with their propellant. Even though modern solids are very safe from accidental ignition, that's still a LOT of weight to carry around; liquid-fueled rocket stages are comparatively lightweight and so shipping isn't nearly as costly or challenging. 

Other things wildly different in KSP is that you can adjust the thrust profile of solids ahead of time: this is typically done by altering the cross-sectional geometry of the solid.  And of course, throttling liquid rockets is vastly harder than shown in KSP.  Still, as far as I know, only NASA uses solids for large amounts of thrust.  This is largely because ICBMs typically use solids or hypergolics.  Most ICBM designs tend towards hypergolics, but such designs became unpopular in the US after a Titan II blew up a good chunk of Arkansas.  This gives Thiokol a larger say in NASA designs than might be otherwise be appropriate.

On the other hand, the ability of SRBs to produce *thrust* relatively cheaply shouldn't be underestimated.  The Shuttle/SLS boosters are the most powerful rocket engines ever launched, exceeded only by the AJ-260 which produced 2000 tons of thrust.  Adding a few boosters with only a minute of burn time can wildly change the amount of cargo you can deliver to orbit.

[magnemoe]

Just now, wumpus said:

Other things wildly different in KSP is that you can adjust the thrust profile of solids ahead of time: this is typically done by altering the cross-sectional geometry of the solid.  And of course, throttling liquid rockets is vastly harder than shown in KSP.  Still, as far as I know, only NASA uses solids for large amounts of thrust.  This is largely because ICBMs typically use solids or hypergolics.  Most ICBM designs tend towards hypergolics, but such designs became unpopular in the US after a Titan II blew up a good chunk of Arkansas.  This gives Thiokol a larger say in NASA designs than might be otherwise be appropriate.

On the other hand, the ability of SRBs to produce *thrust* relatively cheaply shouldn't be underestimated.  The Shuttle/SLS boosters are the most powerful rocket engines ever launched, exceeded only by the AJ-260 which produced 2000 tons of thrust.  Adding a few boosters with only a minute of burn time can wildly change the amount of cargo you can deliver to orbit.

Ariane 5 disagrees with only NASA uses them, but yes agree that the west tend to prefer solid fuel ICBM while most others uses hypergolic. 
This give you high power SRB pretty cheaply as you want to keep the factory open and you are not expecting to use large numbers of ICBM often. 

Scott Manley had an story of something who was more like an Saturn 1 solid first stage level engine tested at KSC

Now this was fueled on side who don't make it sound very high tech but it also blew it nozzle then they tested it with one. 
 

[JoeSchmuckatelli]