I was thinking about all these SciFi stories about how massive amounts of shuttles, and or dropships entering the atmosphere in an invasion force; you'd need quite a lot of them, especially if you had deal with a continent's worth of military power.

 

Now, would all those dropships, fighters etc. heat up the atmosphere when they enter? Enough to any invasion would be accompanied by a heat wave?

I would not think so. Of course this would depend on the amount and size of the drop ships.

 

The reason I would doubt that it would dramatically heat the Earth's atmosphere is that many objects (space junk, rock, small asteroids) from space fall to Earth every second and burn up before hitting the ground most of the time. And, these objects don't cause dramatic heating.

 

So I would fail to see why drop-ships, designed to land on the planet would cause more heat than random objects. Drop-ships like that would most likely be designed to reduce the amount of heat and drag caused by re-entry.

 

However, the larger the ship and faster it is going, the more heat it will produce. So, theoretically it is possible, but improbable.

 

Of course this is my educated opinion, I hope this helps.

Also consider that most ships in science fiction seem to have enough maneuvering power to slow down significantly from orbital velocity, so they don't have to re-enter at 17,000mph. Sometimes they even just hover and gently go straight to the ground.

Also, a lot of the "heat" generated during re-entry is due to compressing the atmospheric gas, rather than frictional heating. This temperature will do nasty things to a spaceship, sure, but it will disappear when the gas moves out of the way of the ship and is no longer compressed. In the end, you're just left with frictional heating, and any heating from the engines if they are used.

 

Actually getting enough ships to invade a planet seems rather unlikely, scifi or not.

The heating is the dissipation of the kinetic energy of the craft traveling at orbital speed. Should be easy to calculate.

you'd need a LOT more of them to cause large scale heating like a heatwave. and most of the energy is dumped in the upper atmosphere where it can just radiate out into space.

Also, a lot of the "heat" generated during re-entry is due to compressing the atmospheric gas, rather than frictional heating. This temperature will do nasty things to a spaceship, sure, but it will disappear when the gas moves out of the way of the ship and is no longer compressed. In the end, you're just left with frictional heating, and any heating from the engines if they are used.

 

Actually getting enough ships to invade a planet seems rather unlikely, scifi or not.

 

i agree, think of all the heavy equipment are military has/needs for a battle. you would need a LOT of ships in order to transport enough people and then equipment....were talking thousands apon thousands of ships.

 

the only effective way to wage a battle would be from space IMO

As Einstein said, "I don't know what weapons World War III will be fought with, but World War IV will be fought with sticks and stones." Now, for space warfare, one way to soften up a planet is to lob asteroids at it. So, it could very well be that we go back to fighting with stones

Well I guess we'll find out soon enough.

 

http://www.popsci.com.au/military-aviation-space/article/2006-12/semper-fly-marines-space

I was thinking about all these SciFi stories about how massive amounts of shuttles, and or dropships entering the atmosphere in an invasion force; you'd need quite a lot of them, especially if you had deal with a continent's worth of military power.

 

Now, would all those dropships, fighters etc. heat up the atmosphere when they enter? Enough to any invasion would be accompanied by a heat wave?

 

It depends on whether the author thinks it helps the plot.

Thanks. I first got the idea after watching a show about the KT impact; thousands of impacting meteorites (bits of Earth falling back down), though didn't strike the ground, heating up the atmosphere enough to ignite foliage.

The space shuttle as a point of reference has around 3.3E12 J of kinetic energy. Assuming there are 100,000 shuttles reentering and all the energy is converted to heat I find,

 

Q = m x Cp x dT

 

dT = 3.30E17 J / (5.15E+18 kg * 1000 J/kg-K) = 6.4E-5 K

 

100 thousand would raise the temperature by 0.00006 Kelvin. To raise the atmosphere an average of one degree would take about a billion reentering shuttles

Only one degree at best? One day, when I'm a famous science fiction writer, I'd hate to have that nitpicked out of my books.

If ETs decided to invade Earth, there would be no contest. If they had the technology to bring them here, they also have technology to easily exterminate selected species. The idea of thousands of spaceships crashing thru the atmosphere, enough to heat it up, sounds ludicrous. There must be many better ways to get rid of us and take over Earth. We would not stand the chance of an ice cube on the Sun.

Well, if I were an alien invading the planet, I would sneak a few pathogen samples, and then make a super deadly disease to wipe the planet (mostly) clean. The pathogens would be unlikely to affect me as most of them require some of the host's specific weaknesses. Alternately, lobbing asteroids would work pretty well too. Massive invasion force, that I'd save for the movies.

Then there's also the amount of resources need to travel to another star system and even more to attack it.

 

It would be easier for them to "Alien-Form"(terraform) their uninhabitable worlds than to try to go to another star system to take another planet; even a planet that has microbes and environment similar to their own by some miracle of chance.