#### kamaz

##### Unicorn hunter
Nuclear pulse propulsion.

4000 tons = 80 T-90 tanks. You'd need over 100 Orions to achieve ground superiosity.

But I have another idea: the venerable Space Shuttle.

The prerequisite is that we have already taken out Venusian in-space and ABM capabilities.

We take the Shuttle, load it with nukes and send to Venus. The Shuttle then performs re-entry and starts dropping nukes while still in the hypersonic or supersonic flight -- the idea here is that it is above the range of Venusian air force, which makes it very difficult to kill. At the same time, it is maneuverable (as opposed to a satellite platform) and can probably fly around the planet with careful planning (think Silbervogel) -- which makes it quite flexible. With enough Shuttles, we could probably destroy most Venusian
assets on the ground.

Then we launch ground invasion forces on Orions.

And once we try to enter the cities, we are dragged into a planet-wide Fallujah (or Stalingrad) :facepalm:

---------- Post added at 02:40 PM ---------- Previous post was at 02:32 PM ----------

Since I know of no way to land an Orion, you also need some sort of landing modules to get your troops through that last 100 miles or so to the surface.

If we're going in armored vehicles (tanks/APCs), that's quite easy. Orion takes us to Venus orbit, and then releases the tanks. Each tank is equipped with an attitude control system, solid rocket motors, ablative shield and parachutes. Once clear of Orion, each tank fires its SRMs retrograde, aerobrakes and lands on a parachute.

#### Artlav

##### Aperiodic traveller
Beta Tester
Open military invasion in this scenario will not work, unless by plot magic.

We will have to resort to economic warfare.
Determine what on Earth Venusians would like, or make products that they would consume.
Establish trading relationships, flood the planet with our products (digital stuff at first, then establish local branches and representatives once the rockets start flying). Send over the missionaries of various confessions and cults.

Get them hooked up, undermine their values, derail their education.
Don't force or condescend - make them pay big \$ for what we provide, make them believe they need it.

A generation or two later the planet should be hooked up like a drug addict.
Then, it's time for us to dictate conditions.

#### Ghostrider

##### Donator
Donator
The problem with interplanetary warfare is that the enemy can see you arriving weeks in advance so forget any surprise factor. You'll be better off staging your own Operation Pastorius and start with a campaign of sabotage to damage enemy communications and transport facilities, then do a massive (and I mean massive orbital drop of troops and materiel in selected key areas where you can entrench and hamper attempts at counterattacks. You'll need a lot of heavy transports and a lot of decoys. We may employ some orbital bombardment. It's gonna be a real knife fight.

One more thing: it's OK to be scared.

#### Spacethingy

As Artlav just pointed out, simply cut their magic supply. Watch as Venus turns back....

OK, sensible answer - I can't really think anythin, other than land a superior force in the planet's large empty areas then attack. Maybe guerrilla tactics? Again, land secretly, then make friends with the smugglers, capture nuclear weapon, hold planet to ransom etc. etc....

Cheaty answer - what's Venus' rare-earth element supply like?

#### T.Neo

##### SA 2010 Soccermaniac
It all depends. How much infrastructure do we want left intact when we take Venus? Regardless to begin with I suggest we send some micro-cubesats equipped with cameras on a close pass in order to gain as complete a map of the surface as possible, at as high a resolution as possible, to allow us to pick out the vital military and logistics hubs.

As much infrastructure intact as possible, as per the .pdf.

General information about Venus- geographic and maritime surveys, satellite images and soforth are publically available, but military surveillance will obviously be required.

Step 4. Detonate the warhead near NEO, so it gets diverted into an orbit which encounters Venus.

That would be a lot more difficult than using a warhead to deflect a NEO away from a planet; one would first require an object on a near pass (of which it is unlikely there are many highly massive ones) and one would also need adequate accuracy to ensure that the trajectory of the object intersects that of Venus.

So there you have it. One launch of Ares-V/SLS per one tank -- without crew or supplies.

In that scenario I don't think launching individual tanks to Venus directly from Earth would be the way to go in any case.

I'm sorry, but even Battlestar Galactica is not going to cut it.

We would need a stargate.

The Battlestar Galactica is an FTL capable space battleship more than a kilometre long and roughly half a kilometre in width.

If you had that kind of technology landing thousands of tanks on Venus probably wouldn't be a problem.

Just a thought. What would the maximum speed we could make a 50 ton block of metal (or anything nice and solid really) hit the surface be? Because Kinetic Kill weapons could be viable.

According to kamaz' velocity values, a 50 ton mass would have a kinetic energy of nearly 700 tons of TNT. Quite powerful, but not a WMD. However, it would be more efficient to utilise such a weapon with submunitions or as a cluster weapon for greater effect. 10 000 darts massing 50 tons total, spread over a 20km by 5km ellipse, would have a dart impact on average every ~8000 m^2, with each dart having an energy of around 50 kg TNT assuming 9000 m/s velocity at impact.

Of course, 50 tons is equivalent to nearly 140 [ame="http://en.wikipedia.org/wiki/W88"]W88[/ame] warheads, with a combined yield of 66 megatons.

Are Venusian ICBM's able to send nuclear weapons to Earth?

No, the ICBMs described in the .pdf are similar to modern ICBMs on Earth- so Trident II, RS-24, etc. Range ~12 000 in surface-to-surface applications, maximum apoapsis ~5500 km if fired straight up.

The primary difference is that these missiles are designed to be able to engage orbital targets. Some may hold non-nuclear interceptor vehicles for this purpose.

The Venusians could launch nuclear warheads toward Earth if they wanted, the situation described in the .pdf merely bottlenecks that capability to their space launch assets.

I'd say none. It has no atmosphere, is easily observable by Terrans and you can easily destruct any Venusian effort. I doubt you can somehow sneak a big enough spacecraft to serve as a lunar base to the Moon without anyone looking for NEO noticing, followed by an Earth government launching something to intercept you. "It's not an asteroid, it's a Venusian colony ship!"
And even if you can and were not detected for some time: The moment you use it it becomes clear that somewhere on the Moon is a base. That becomes top priority, gets found and destroyed. Now Terrans know that strategy...

The Moon might, however, play a very large role from the Terran perspective. It is nearby, it has a relatively shallow gravity well, and can be mined for resources including various metals and hydrolox. A war effort would undoubtedly be very large, which makes the economies of scale for establishing lunar industry attractive; even if many components are not constructed on the Moon, the bulk of the mass of various assets could be- which would mean that far less mass would need to be lifted from Earth.

Kessler Syndrome is the orbital equivalent of a minefield, and requires no upkeep patrols.

That's one possibility for orbit denial, but the Venusians will probably value the space near their planet as well, for various reasons. Of course, detonation of nuclear weapons near the planet will cause big problems as well, depending on how well-hardened their satellites are, and also depends on whether a magnetosphere is present around the planet (real Venus does not really have a magnetosphere, and I did not specify whether this Venus does in the .pdf, but given that it has an Earth-like rotation let's assume that it does). Regardless of the presence of a magnetosphere, nuclear detonations near the atmosphere will also potentially produce an EMP effect, which could wreak havoc on civilian systems even if military ones are adequately hardened...

Another factor to consider is that space debris is usually discussed in the context of vehicles that operate for years; in this scenario, weapons or spacecraft may transit the orbital bands in question in just a few hours, which would greatly reduce their exposure.

Troops would need to have either aeroshells like the ODSTs from Halo/Mobile Infantry from Starship Troopers (Airborne infantry equivalent) or an assault shuttle, like the MOVIE version of S.T. and the Halo Pelican (landing craft a la Normandy). Larger ships, like the TAV Valkyrie from Avatar, would fulfill the heavy assault role to deploy tanks after landing (C-5 equivalent).

Having something like the TAV on hand would certainly make things easier, it's basically a transport aircraft that is also an easily reusable SSTO. Of course, the technology of the TAV as it is described is certainly quite advanced; it has an onboard fusion engine with sufficient T/W to propel it effectively during the latter part of its ascent...

I feel it all boils down to HOW one transports the massive assault force from Earth to Venus. After you get boots on the ground, and set up a foothold on Venus, it's a "conventional" war. You just have to bring all your reinforcements with you at the start: there's no calling the Pentagon and asking for a battalion of fresh troops and getting them in a week by airlift. You have to wait for the next transfer window.

That's quite true, with two caveats;

1. You might be able to bend the boundaries of the windows a bit if you're willing to lose performance, so a transport vessel that would otherwise be able to carry hundreds of vehicles, for example, might be able to transport tens of vehicles a few weeks outside of the transfer window if they are badly needed.

2. There is a space combat element as well, which in conventional war is limited to surveillance and communications, but can be used here for offense and defence. We're not merely talking about orbital bombardment, but also the possibility of orbital assets being used to intercept surface-to-surface missiles as a sort of tactical version of SDI.

bioweapons. Need I say more?

Not a good idea if the aim is to avoid civilian casualties to the greatest degree possible.

But the Venusians have telescopes and they can see your Battlestar weeks in advance. How do you prevent them from intercepting you before landing?

You don't. Welcome to space warfare.

And even if you somehow make it to landing, they will see your reentry -- what is stopping them from covering your landing site with artillery fire and/or nukes immediately after touch down?

That's a very good question and stuff like this is why I wanted to start this discussion in the first place.

Nuclear pulse propulsion.

Nasty, expensive, and dirty, but it's the only thing I can think of that gives you the upmass you need to carry anything heavy to Venus.

As kamaz mentioned, the mass of the example you cite is equivalent to only 80 tanks- so either multiple vessels would be needed, or the vessel would need to perform multiple round trips (somehow) to lift the necessary mass...

But it does recall the massive Orion Space Battleship that was alledgedly presented to President Kennedy...

And also the Ithacus intercontinental troop transport concept...

But I have another idea: the venerable Space Shuttle.

The prerequisite is that we have already taken out Venusian in-space and ABM capabilities.

We take the Shuttle, load it with nukes and send to Venus. The Shuttle then performs re-entry and starts dropping nukes while still in the hypersonic or supersonic flight -- the idea here is that it is above the range of Venusian air force, which makes it very difficult to kill. At the same time, it is maneuverable (as opposed to a satellite platform) and can probably fly around the planet with careful planning (think Silbervogel) -- which makes it quite flexible. With enough Shuttles, we could probably destroy most Venusian
assets on the ground.

Well, using the historical shuttle would be a no-go way back at the point of getting it out of orbit, as it was never intended for BEO flight.

Technically a satellite in a polar orbit should be able to hit any location on the planet within a day. I'd imagine a craft in the upper atmosphere would be more limited in terms of its ground track (there is some crossrange, but it cannot cover the entire planet easily), as it's only likely to be able to circle the planet once or so unless it's in powered flight (in which case fuel is a limitation) and there are obviously thermal concerns as well, in addition to the technical difficulty of separating a munition from a vehicle travelling at hypersonic speed.

The problem with interplanetary warfare is that the enemy can see you arriving weeks in advance so forget any surprise factor. You'll be better off staging your own Operation Pastorius and start with a campaign of sabotage to damage enemy communications and transport facilities, then do a massive (and I mean massive orbital drop of troops and materiel in selected key areas where you can entrench and hamper attempts at counterattacks. You'll need a lot of heavy transports and a lot of decoys. We may employ some orbital bombardment. It's gonna be a real knife fight.

The problem with a sabotage operation is it isn't going to be easy to conduct, you can't drop off operatives unannounced and there isn't really anyone with ethnic or national connections on Venus that can be used to aid an invasion.

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#### Andy44

##### owner: Oil Creek Astronautix
As kamaz mentioned, the mass of the example you cite is equivalent to only 80 tanks- so either multiple vessels would be needed, or the vessel would need to perform multiple round trips (somehow) to lift the necessary mass...

Yes, so you build a fleet of these things.

And although the pic I posted says 4000 tons these things scale up so you can make them much bigger and heavier. In fact, the beauty of Orion is that the bigger it is the more efficient it is and the higher the effective Isp. There is a practical limit, of course, but if are seriously considering taking and holding an entire earth-size planet using current tech you will need at least a fleet of Orions, just for starters.

Look at the size of the fleet used just to invade Okinawa in WWII. All of this for a relatively small land mass which has already been cut off from outside help.

And you want to scale this up to invade a planet?! Good luck.

#### BruceJohnJennerLawso

##### Dread Lord of the Idiots
The problem with interplanetary warfare is that the enemy can see you arriving weeks in advance so forget any surprise factor. You'll be better off staging your own Operation Pastorius and start with a campaign of sabotage to damage enemy communications and transport facilities, then do a massive (and I mean massive orbital drop of troops and materiel in selected key areas where you can entrench and hamper attempts at counterattacks. You'll need a lot of heavy transports and a lot of decoys. We may employ some orbital bombardment. It's gonna be a real knife fight.

One more thing: it's OK to be scared.

Are lasers any good for the bombardment, or are missiles needed?

I would propose a slightly altered idea, due to the incredible difficulty involved in terraforming Venus with its slow rotation: The invasion is proceeding as scheduled, but the Venusians are concentrated in large floating complexes at reasonable altitudes above the surface (ie where the current environment is reasonable enough for humans if you ignore the sulfuric acid :shifty

This makes the invasion a little easier, since the Venusian lift capabilities may be far less than those of Earth, but sending warheads doesn't make sense any more because the cities can move themselves...

#### MaverickSawyer

##### Acolyte of the Probe
[snip]
Having something like the TAV on hand would certainly make things easier, it's basically a transport aircraft that is also an easily reusable SSTO. Of course, the technology of the TAV as it is described is certainly quite advanced; it has an onboard fusion engine with sufficient T/W to propel it effectively during the latter part of its ascent...[/snip]

Who said anything about a return to orbit with a full payload? Give it just enough propulsion to deorbit itself, and the VTOL engines for later use, and just drop it into the atmosphere. The turbine engines would give you SOME post-entry crossrange capacity, as well as adding a much-needed air mobility aspect. Bring along a LOT of parachutes for air drops, too.

#### Ghostrider

##### Donator
Donator
Missiles that could hit Earth from Venus and the reverse would not be ICBMs, but IPMs (InterPlanetary Missiles). Basically they would be landing planetary probes (hail!) with nukes in place of the sensor packages. They're already feasible with current tech, you don't have to soft-land them but you need manoeuverable warheads, again possible with current tech.

#### kamaz

##### Unicorn hunter
That would be a lot more difficult than using a warhead to deflect a NEO away from a planet; one would first require an object on a near pass (of which it is unlikely there are many highly massive ones) and one would also need adequate accuracy to ensure that the trajectory of the object intersects that of Venus.

Whatever; the main point was that the most energy-efficient way of waging interplanetary warfare is to use asteroid mass, because its already up in the gravity well.

The Battlestar Galactica is an FTL capable space battleship more than a kilometre long and roughly half a kilometre in width.

If you had that kind of technology landing thousands of tanks on Venus probably wouldn't be a problem.

Removing FTL -- which I believe is against the rules -- Battlestar is basically an aircraft carrier in space. It is very good for destroying orbital assets, but it cannot be landed on planet in one piece, and even if it could be landed, it would become a big, fat, sitting duck. And it is still too small to put 20K tanks on Venus.

If I can have FTL, then I'm sticking FTL drive to each tank and teleport them directly from Earth surface to Venus surface. Or better yet, I teleport an assassin to the bedroom of Venusian leader.

Of course, 50 tons is equivalent to nearly 140 W88 warheads, with a combined yield of 66 megatons.

But one ton of rock is much cheaper than one ton of nuclear warhead, especially is the rock is asteroid, so it does not have to be lifted up from Earth's gravity well.

The Venusians could launch nuclear warheads toward Earth if they wanted, the situation described in the .pdf merely bottlenecks that capability to their space launch assets.

But you didn't describe what launch capabilities our side has. If the agressor is US or Russia, then the launch capabilities are on par: both sides have one equatorial and one launch site, which is not enough to wage a full-scale war.

And lauch pads are easily visible from space. So I'd rather imagine the situation evolve towards an arms control treaty: both sides will agree to keep their lauch capabilities below a certain level to avoid expensive arms race.

A war effort would undoubtedly be very large, which makes the economies of scale for establishing lunar industry attractive; even if many components are not constructed on the Moon, the bulk of the mass of various assets could be- which would mean that far less mass would need to be lifted from Earth.

And the problem here is that you have handwaved the reason for the war.

If you want to go to Venus for resources/land, it makes no sense, because they can be obtained on Mars or elsewhere for a fraction of the invasion cost.

If you want to conquer Venus because you hate Venusians, then diverting asteroids is much cheaper than sending tanks.

That's one possibility for orbit denial, but the Venusians will probably value the space near their planet as well, for various reasons.

If I was on Venus, I would load all my ICBMs with nails and launch them into polar orbits. That gives me an impenetrable shield which will last anywhere from weeks to thousands of years depending on altitude chosen.

ICBMs are ground-based and can be launched on short notice. So, I'd launch my Kessler shield into low attitude (so it decays after, say, 1 year) after your army has already done Trans-Venus Injection. I can live without one year of space access, but your army cannot sit in Venus orbit for one year, because you don't have consumables. In fact, your army would be probably launched using the most mass-effcient scheme, which means direct entry -- straight into my Kessler shield. Oops.

And if you are really stubborn, I can create a Kessler shield above the Venus-stationary orbit. That will deny you access to Venus permanently, but leave all interesting orbits usable.

Then it's a race who first builds the FTL

#### MattBaker

##### New member
Or better yet, I teleport an assassin to the bedroom of Venusian leader.

With a that unified people...You just gave them a reason to hate you and brought another guy to power who might hate Terrans. Might not be the best thing to do.

In my opinion this still isn't possible in any way with convential warfare. If there is some kind of trade smuggling in a dozen of wasps, uh, persons isn't that hard. But then there's the main problem with such an...equal, unified population. It seems hard to start any kind of revolution there. Also you probably can't get Terrans in power but rather another of your agents who operates as a high-ranking Venusian. And how did he get in that position?

Also about the nuclear warheads: How about having one or two warheads with tiny upper stages put into an Earth orbit with your usual launches like NROL, Progress vehicles, communication satellites (yeah, we'll just launch a freaking nuclear weapon bolted to our giant controlled explosion, sounds safe!) over some time so you can do this without anyone noticing and then each could get send to Venus whenever you fancy it. Plus single or dual warheads with a small upper stage aren't really big and could get to Venus without anyone noticing. At least until the first one hits. Because Venusian space research doesn't seem to go beyond Venus orbit, does it? So could they track a relatively small, not more than 5x2 meter object in deep space? Even if so shooting down individual warheads, especially when their numbers are in the dozens seems much harder than shooting down your large invasion fleet.

#### T.Neo

##### SA 2010 Soccermaniac
Well, it is quite obvious that modern lift and spaceflight capabilities are woefully inadequate; the next step is to determine what technology and infrastructure is necessary. What is the necessary size and disposition of the forces needed to invade Venus? How should they be landed on the planet? And what role should bombardment of enemy assets from space take prior to invasion? What spin-off effects do the necessary technologies for sufficient interplanetary transport have on land, air and space combat?

Look at the size of the fleet used just to invade Okinawa in WWII. All of this for a relatively small land mass which has already been cut off from outside help.

And you want to scale this up to invade a planet?! Good luck.

I am well aware of the scale involved as per the creation of the figures in the .pdf, my contention is merely that repeatedly launching multi-thousand-ton spacecraft from friendly territory using nuclear bombs is probably not something to be treated lightly. The total yield expended would probably exceed that of a hypothetical cold war nuclear exchange.

Who said anything about a return to orbit with a full payload? Give it just enough propulsion to deorbit itself, and the VTOL engines for later use, and just drop it into the atmosphere. The turbine engines would give you SOME post-entry crossrange capacity, as well as adding a much-needed air mobility aspect. Bring along a LOT of parachutes for air drops, too.

True, that'd make a very capable landing platform. My point is that a vehicle able to make a round trip is (theoretically) reusable, which means that a fleet of vehicles can be used to transport considerably more mass than they would be able to if they were one-use only.

Whatever; the main point was that the most energy-efficient way of waging interplanetary warfare is to use asteroid mass, because its already up in the gravity well.

Effective weapons are not only energy efficient though; there are also other concerns. A dirigible would be a more energy efficient platform for delivering nuclear warheads than an intercontinental missile- but naturally it would be useless in any realistic scenario.

Removing FTL -- which I believe is against the rules -- Battlestar is basically an aircraft carrier in space. It is very good for destroying orbital assets, but it cannot be landed on planet in one piece, and even if it could be landed, it would become a big, fat, sitting duck. And it is still too small to put 20K tanks on Venus.

I merely mentioned the FTL to point out the science-fictiony-ness of the Battlestar.

Simply because the Battlestars in canon were 'space aircraft carriers' doesn't mean a vehicle of similar size and technology could not be adapted for a different role. As one can see (link) the Battlestars are very large- the flight pods alone are larger than a CVN.

But one ton of rock is much cheaper than one ton of nuclear warhead, especially is the rock is asteroid, so it does not have to be lifted up from Earth's gravity well.

You'll need approximately 100 000 tons of rock to be equivalent to a one ton warhead (assuming impact velocity of 10 km/s), which does equal the playing field somewhat. The rock will have to be moved by a propulsion system of some kind, from several tens to several thousand m/s depending on how much you're willing to be tactically limited by the orbits of available objects.

Furthermore, a rock does not make a very good kinetic weapon for deployment against a planetary surface- all concepts on the subject, to my knowledge, involve purpose-made projectiles that are long and thin, and made of a dense material suitable for surviving re-entry intact. There's no assurance that a random piece of rock will even remain in one piece, let alone have a similar accuracy and terminal effect to a tungsten dart or rod.

Asteroids as kinetic weapons only makes sense if one wants (1) an indiscriminate weapon and (2) has the capability to perform large-scale asteroid redirection, which is a good deal above mere deflection.

But you didn't describe what launch capabilities our side has. If the agressor is US or Russia, then the launch capabilities are on par: both sides have one equatorial and one launch site, which is not enough to wage a full-scale war.

The aggressor is Earth as a whole, which includes the capabilities all nations can bring to bear.

And the problem here is that you have handwaved the reason for the war.

Correct.

If you want to go to Venus for resources/land, it makes no sense, because they can be obtained on Mars or elsewhere for a fraction of the invasion cost.

Technically in this scenario the only habitable land available is on Venus and Earth...

If I was on Venus, I would load all my ICBMs with nails and launch them into polar orbits. That gives me an impenetrable shield which will last anywhere from weeks to thousands of years depending on altitude chosen.

ICBMs are ground-based and can be launched on short notice. So, I'd launch my Kessler shield into low attitude (so it decays after, say, 1 year) after your army has already done Trans-Venus Injection. I can live without one year of space access, but your army cannot sit in Venus orbit for one year, because you don't have consumables. In fact, your army would be probably launched using the most mass-effcient scheme, which means direct entry -- straight into my Kessler shield. Oops.

And if you are really stubborn, I can create a Kessler shield above the Venus-stationary orbit. That will deny you access to Venus permanently, but leave all interesting orbits usable.

In the .pdf the Venusians are described to have 1170 ICBMs total. Assuming that the average payload to orbit is ~2800 kg, the total liftable mass (not counting fairings, upper stages, etc) is around 3400 tons. Assuming that the kinetic mines are 1 cm iron spheres, this would equate to over 820 million in orbit. The volume of the entire orbital sphere between 180 and 300 km is approximately 6e19 m^3, which equates to an average of 1e-11 mines per cubic meter.

If we model the orbital track of a spacecraft as a torus, assuming an altitude of 250 km and a spacecraft width of 100 meters, we have a volume of 1.5e11 m^3- which means that on average, there will be roughly a single mine within the vehicle's entire orbital track at any one time.

I would hardly consider that an insta-kill minefield. Vehicles passing through the layer to the surface would have an even lower level of exposure, and few attacking vehicles would be likely to orbit at such an altitude anyway as it is well under the Venusian ABM ceiling.

Increasing the altitude of the field will mean that the particles remain in orbit longer; eventually you get to the point where their presence is functionally indefinite. In addition, the further out you go, the greater the amount of particles will be needed to achieve the same density. For example, at 40 000 km, a shield with the same width and density will need 40 times the mass- and relative velocity between orbiting objects will be lower, which makes each mine less dangerous individually.

Of course, since the planet's surface and all interesting orbits are within the shield, all incoming weapons and spacecraft will not orbit within it constantly- thus maximising their exposure- but instead merely pass through it once.

#### Artlav

##### Aperiodic traveller
Beta Tester
So, clarifying the limits:
-No smart solutions, like planting seeds of dissent or economic warfare. It should be an actual direct invasion.
-No specific purpose for the invasion, just A God Said So (tm).
-United forces of Earth acting against United Venus (at least at the start, their counter-attacks aimed at breaking our not-quite-unified world's alliance are plausible).
-The magic is off-limits.
-The enemy is also smart.

Questionable:
-No tactics involving covert purposes and camouflage (i.e. we need Beachhead Island for a science station)?
That is a big point - can we start off with good relations between planets, and thus an ability to smuggle some hardware to Venus unimpeded under that's cover?
I'll assume not.

-Our own military do not have any real modern warfare experience - most wars fought these days are technologically anisotropic.
Are we really better than them?
At least we had some wars, and some strategic and tactic experience, while they were doing nothing but parades for the last century or so.

Strategy:
-Local resource utilization is mandatory, since we have no practical ways of invasion-scale transport.
-Transport bare bones equipment, plutonium and other rare materials, defensive hardware, etc, along with enough personnel to handle it.
-Use large fraction of remote controlled equipment, AI controlled if possible.

What sort of technology we will need?
-Weapons and weapon platforms that are quickly and easily manufactured from low-level resources.
-Exponential manufacturing power.

A compact factory package that can produce various useful stuff from low-level materials, including itself.
Von-Neuman machines would be good, but basic factory that can make itself should suffice.

The factories would replicate, at least conceptually.
In practice it would likely be troop-assisted replication - factories make the parts, squads yank them together.
Automating the last 5% of the process would likely cost a lot of extra complexity that we can't afford.

As the manufacturing capability grow, some of it should get diverted to making military assets.
This way we can increase our forces nearly exponentially, on site.

Obvious problem #1:
No one would let us just sit there building armies and factories - there is no stealth in space, they'll know we're coming months in advance.
So, we need to keep the beachhead defended long enough to build up the capability.
Here ability to start off from a science station or embassy would have came in handy, since we would have some quiet start-up time.

Obvious problem #2:
We can attack with RC/AI equipment, but we would need troops to hold ground.

From here it's an iterative process - think up a way to land, think up a way to defend, think up countermeasures, etc. Whoever ends up playing on the highest level wins.

So, let's see.
We need to land, and have time to build up strength on site.
That means penetrating defences and preventing them from nuking us off the site.

They can see us, but we will not be thrusting - just coasting, so it's not easy to tell real targets from decoys.
Put lots of decoys on the transfer.
A cloud of equipment going from Earth to Venus, on various trajectories.
Some of it would be decoys, some would be point strike weapons (i.e. tungsten rods with guidance), some will be nuclear warheads.

A grand total of one or two Orion-sized launchers, or a plausible fleet of present day rockets.

Best place to land is a remote location inland - then their big navy won't get to us.
The nukes should be detonated high above the atmosphere, to destroy satellite surveillance and communication, as well as to render as many of the equipment inoperable as possible by EMP.
Rest of the nukes target the launch sites and known ICBM sites.
Bust a dam or two with spare nukes.
Tungsten rods should impact at highly specific targets likely to be surrounded by civilian stuff - command centres, power plants, and so on.
Some of the weapons should be spared for some nonsense targets, clearly aimed at and hit.

That is, wreak as much chaos and confusion as possible, without destroying too much civilian targets.

Under that cover we can land.
Transports should be incoming towards an obvious, but fake landing location, where the enemy forces would likely place an ambush.
The trajectories should be altered at the last possible moment, to land in the real location, hopefully unguarded.

Establish defences while the chaos lasts, start building.

Venus's turn.

#### kamaz

##### Unicorn hunter
Spacecrafts, especially their thermal insulation, are very fragile things.

Investigation into the Columbia disaster found that RCC tile has been destroyed by a piece of foam weighting 1.6lb and travelling at 800mph -- which corresponds to kinetic energy of about 20kJ.

A mass of 0.1g travelling at the speed of 10km/s (orbital velocity) has energy of 50kJ -- which is enough to fatally damage thermal insulation as demonstrated above.

The Venusian ICBM arsenal is enough to lift 3.27e10 such shards into orbit. Surface of sphere 100km above Venus is 4.73e14 square meters, so my shard density would be 1e-4 shards per square meter. Indeed, 4 orders of magnitude too low.

However, I have now realized then I don't have to built a Kessler shield covering the whole planet. What I can do much more easily (and without denying myself access to space) is to turn my ICBMs into ASAT weapons by loading them with shards, launching straight up, and detonating in front of your reentering spacecraft. This is equivalent to your spacecraft plowing through a cloud of shards at 10km/s -- where a single collision is enough to cause catastrophic failure during aerobraking. With 2800kg payload I have 2.8e7 shards per missile. If distributed evenly in a sphere 1km in radius, this is 0.006 shards per cubic meter. If your spacecraft has 10m^2 cross-section (which quite small), then it has 6% probability of receiving one impact with each meter it is travelling within the cloud. This means 95% kill probability if the spacecraft travels 50m within the cloud and 99.8% kill probability if it travels 100m within the cloud. If it flies through the center of the cloud (i.e. travels 2km in the cloud), then the expected number of impacts it receives 120.

---------- Post added at 11:29 PM ---------- Previous post was at 11:07 PM ----------

Venus's turn.

Everything landed? Good.

Even assuming that land-based assets have been destroyed completely,
Venus still has 30 ballistic subs with 24 missiles on each = 720 missiles.

Use naval aircraft and whatever is remaining of the airforce to locate landing sites. Transmit coordinates to submarines. Use 10 subs to nuke the landing sites.

[ame="http://en.wikipedia.org/wiki/Samson_Option"]Samson option[/ame]: Remaining 20 subs hide below the ice caps, with orders to launch missiles on main population and economic centers in six months unless further orders are received.

---------- Post added at 11:44 PM ---------- Previous post was at 11:29 PM ----------

Best place to land is a remote location inland - then their big navy won't get to us.

Even if Venusian navy can't destroy the invading forces (which I doubt, given that it has sub-launched nukes), it can still cordon off the island.

We get to keep the island, but that's all we can do.

#### Artlav

##### Aperiodic traveller
Beta Tester
Even assuming that land-based assets have been destroyed completely,
Venus still has 30 ballistic subs with 24 missiles on each = 720 missiles.

Use naval aircraft and whatever is remaining of the airforce to locate landing sites. Transmit coordinates to submarines. Use 10 subs to nuke the landing sites.
ABM plus early warning satellites should take care of most of the missiles.
Same with allowance for holes in the coverage, shot down satellites and other countermeasures adds up to a dozen of missiles impacting per landing site.

Good news is, it will take time to organize, and more time to pin-point the locations under the jungle cover (we altered our trajectories after the nukes blinded most surveillance, so hopefully they won't know precise enough locations right away) - we should have days to dig in and/or spread out.

Spreading out might be a bad idea, due to general lack of forces and likely presence of at least basic enemy militia and guerrillas in the region.

So, move rapidly away from tell-tale signs of landing, set up ABM and AA sites, then dig down for a rain of nukes. A mountainous or cave-rich landing site would have been perfect.

Leave obvious signs of activity some distance off - with luck it will divert or spread out the impacts.

Remaining 20 subs hide below the ice caps, with orders to launch missiles on main population and economic centers in six months unless further orders are received.
No ice caps.
But no real need for them - a sub is difficult to find as it is.

I'll file that option as a late problem - first we need to establish ourselves.
Then, either we negotiate the surrender, or capture the codes to send the fake message, or make that plan public to get the people scattered, etc.

Even if Venusian navy can't destroy the invading forces (which I doubt, given that it has sub-launched nukes), it can still cordon off the island.

We get to keep the island, but that's all we can do.
There are landmasses, that is continents, besides the islands. That is where we land.

Even if it's an island, that does not change the situation too far off.
A blockade is even to our advantage in that scenario - we would still have a constant supply of weapons due to on-site manufacture, that include aircraft and bombs. Breaking through the navy should be possible then, given enough time.

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#### PhantomCruiser

##### Wanderer
Moderator
Tutorial Publisher
"I say we take off and nuke the entire site from orbit. It's the only way to be sure"

On further reflection all I can think of is to throw rocks at them like had been previously mentioned. A couple of iron bowling balls a few Km across could be done with some precision mathmatics and a few nukes. Still be expensive though.

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#### MaverickSawyer

##### Acolyte of the Probe
Hrm... pack along a number of SM-3 or THAAD launchers and missiles in the initial landing force. Nukes are not as serious of a problem. Some MIGHT get through, but the vast majority won't.

However, if you land close to one of their population centers, they might be less inclined to nuke you right away, and you'd have access to their infrastructure right away. Or, if things REALLY go south, you have access to lots of hostages. :shifty:

#### T.Neo

##### SA 2010 Soccermaniac
No smart solutions, like planting seeds of dissent or economic warfare. It should be an actual direct invasion.

Planting seeds of dissent is difficult due to the political situation; I'm not entirely sure how economic warfare would work as there's not really anything you can trade between the two planets that can't be more economically manufactured in-situ.

-No specific purpose for the invasion, just A God Said So (tm).

Basically.

-United forces of Earth acting against United Venus (at least at the start, their counter-attacks aimed at breaking our not-quite-unified world's alliance are plausible).

Venusian counterattacks to destabilise Earth would be more plausible than Terran subterfuge to destabilise Venus, obviously- but I suspect short of attacking a nation with a WMD and placing the blame on another nation, no attack would really be that effective.

-The magic is off-limits.

Yes; this is one of the reasons I went for magic rather than a technological solution.

-No tactics involving covert purposes and camouflage (i.e. we need Beachhead Island for a science station)?
That is a big point - can we start off with good relations between planets, and thus an ability to smuggle some hardware to Venus unimpeded under that's cover?
I'll assume not.

I did not assume so originally, but even if there was considerable transport between the two planets, how would one smuggle a considerable amount of military hardware there? Performing a modern invasion, covertly (even only in part), seems impossible enough between nations on Earth- how would one do it between planets?

-Our own military do not have any real modern warfare experience - most wars fought these days are technologically anisotropic.
Are we really better than them?
At least we had some wars, and some strategic and tactic experience, while they were doing nothing but parades for the last century or so.

The same can be said of any modern conflict between peer opponents, to a degree. And I wouldn't say the Venusians have only been doing parades; they obviously have training exercises and soforth to optimise competence wherever they can, though obviously the lack of combat experience of any kind imposes obvious disadvantages.

Strategy:
-Local resource utilization is mandatory, since we have no practical ways of invasion-scale transport.
-Transport bare bones equipment, plutonium and other rare materials, defensive hardware, etc, along with enough personnel to handle it.
-Use large fraction of remote controlled equipment, AI controlled if possible.

What sort of technology we will need?
-Weapons and weapon platforms that are quickly and easily manufactured from low-level resources.
-Exponential manufacturing power.

A compact factory package that can produce various useful stuff from low-level materials, including itself.
Von-Neuman machines would be good, but basic factory that can make itself should suffice.

The factories would replicate, at least conceptually.
In practice it would likely be troop-assisted replication - factories make the parts, squads yank them together.
Automating the last 5% of the process would likely cost a lot of extra complexity that we can't afford.

As the manufacturing capability grow, some of it should get diverted to making military assets.
This way we can increase our forces nearly exponentially, on site.

I can believe a bootstrap industrial infrastructure on a planetary surface with sufficient seed mass and design detail solved, but under invasion conditions? How long can we expect such a factory to produce enough assets to make an invasion viable? How does it access the necessary materials for production of war assets? A round of ammunition, a missile, a ground vehicle contain a variety of metals in their various alloys, as well as a number of other chemical resources- these will all have to be acquired. How does the need to establish and maintain a supply chain to these resource sites (especially if they may be somewhat geographically distant) affect tactical considerations?

Earlier I was wondering if local fuel, food and factories could be captured- but things like factories and fuel depots are very easy for the enemy to destroy if forced to retreat...

I know you mention starting from an embassy, for example, and maybe you're thinking of something slightly different from the norm, for the purposes of this scenario, but generally in my experience an embassy is a small-to-medium sized administrative building in an urban area- hardly a suitable place to set up an invasion factory.

Meanwhile modern forces can get around a planet very quickly- even from the antipode of the target, the fastest transports can reach it in days, and the fastest weapons in around an hour. The time it takes to mount an attack on such a beachhead is much faster than the time it should take to construct adequate assets

There are landmasses, that is continents, besides the islands. That is where we land.

Most of the population is located on several of the larger landmasses- many of the islands are sparsely populated and unimportant, with some being entirely uninhabited.

Spacecrafts, especially their thermal insulation, are very fragile things.

Thermal insulation can be shielded until needed, and it may be possible to make the TPS system of a landing craft somewhat more durable than the shuttle TPS.

a 1.6lb piece of foam travelling at 800 mph and an 0.1 gram shard travelling at several km/s also have very different impact dynamics. Whether this is better or worse from a TPS robustness perspective is another matter entirely...

The Venusian ICBM arsenal is enough to lift 3.27e10 such shards into orbit. Surface of sphere 100km above Venus is 4.73e14 square meters, so my shard density would be 1e-4 shards per square meter. Indeed, 4 orders of magnitude too low.

The shell around the planet is not one-dimensional, however- so the appropriate form of measurement would be particles per cubic meter.

However, I have now realized then I don't have to built a Kessler shield covering the whole planet. What I can do much more easily (and without denying myself access to space) is to turn my ICBMs into ASAT weapons by loading them with shards, launching straight up, and detonating in front of your reentering spacecraft. This is equivalent to your spacecraft plowing through a cloud of shards at 10km/s -- where a single collision is enough to cause catastrophic failure during aerobraking. With 2800kg payload I have 2.8e7 shards per missile. If distributed evenly in a sphere 1km in radius, this is 0.006 shards per cubic meter. If your spacecraft has 10m^2 cross-section (which quite small), then it has 6% probability of receiving one impact with each meter it is travelling within the cloud. This means 95% kill probability if the spacecraft travels 50m within the cloud and 99.8% kill probability if it travels 100m within the cloud. If it flies through the center of the cloud (i.e. travels 2km in the cloud), then the expected number of impacts it receives 120.

Utilising ABM and ASAT weaponry as described in the .pdf (or the logical evolution thereof) is a far more viable option. The missiles described for such systems are far lighter than full-scale ICBMs, and therefore likely cheaper and easier to move around. A direct hit with such a missile on a reentering spacecraft would likely have a 100% kill probability.

Remaining 20 subs hide below the ice caps, with orders to launch missiles on main population and economic centers in six months unless further orders are received.

There are no ice caps, as per the .pdf.

Such a scheme would serve to do nothing but meaninglessly kill millions of Venusian citizens. It won't even serve to spite the Terran invaders much, as they aren't invading for the economic worth of the population or economic centers on the planet.

A mountainous or cave-rich landing site would have been perfect.

Can natural caves be used to hide hundreds of thousands of tons of equipment?

Hrm... pack along a number of SM-3 or THAAD launchers and missiles in the initial landing force. Nukes are not as serious of a problem. Some MIGHT get through, but the vast majority won't.

Depending on how durable the beachhead is to nuclear attack, how concentrated the forces are and the surrounding terrain, a few warheads might be enough to cause severe trouble.

And there are also other avenues of attack that need to be defended against- such as cruise missiles or naval airstrikes.

#### Artlav

##### Aperiodic traveller
Beta Tester
I did not assume so originally, but even if there was considerable transport between the two planets, how would one smuggle a considerable amount of military hardware there? Performing a modern invasion, covertly (even only in part), seems impossible enough between nations on Earth- how would one do it between planets?
...
I know you mention starting from an embassy, for example, and maybe you're thinking of something slightly different from the norm, for the purposes of this scenario, but generally in my experience an embassy is a small-to-medium sized administrative building in an urban area- hardly a suitable place to set up an invasion factory.
An embassy is one of the worst choices, a science outpost would have been much better.
But i'm not talking about smuggling in an invading army, but a seed factory or two, to be covertly moved into some less obvious location, with the rest of the plan as described.

I can believe a bootstrap industrial infrastructure on a planetary surface with sufficient seed mass and design detail solved, but under invasion conditions? How long can we expect such a factory to produce enough assets to make an invasion viable? How does it access the necessary materials for production of war assets? A round of ammunition, a missile, a ground vehicle contain a variety of metals in their various alloys, as well as a number of other chemical resources- these will all have to be acquired. How does the need to establish and maintain a supply chain to these resource sites (especially if they may be somewhat geographically distant) affect tactical considerations?
That is the main problem, that places this into "what sort of technology we will need" category.
We can not rely on landing smack into a nexus of all ores and minerals.

That means the "low level resources" would have to be whatever you can get from soil, sand, rock, organics, and other stuff abundant on a surface of Earth-like planet.

We would have to use composite materials, high-order carbon molecules, polymers of all sorts, silicon nanocomposites - various things that can be synthesised from these resources.
The machinery we would build would be mostly these, instead of metals.
Nanocomposite armour and ceramic or plastic guns are plausible, and potentially present day tech.
Combustion chambers and similar engine parts would be tricky.
The fuels used are likely hydrogen (modern internal combustion engines work off it as is), or easy to manufacture hydrocarbons, like alcohol or simple oils.
Power will come from nuclear reactors (which are not replicable, and plutonium is non-renewable), and be used to produce fuels and run factories.

An entire ecosystem of machinery would have to be developed.

Time is another big issue - caves and trenches would let us survive the first day's "nuke them off the site" counterattacks, but for the following weeks or months we would have to stand ground against an organized and planned counter-assault.

So, being blockaded on an island could be a very good option - drag the negotiations while the factories breed.

How long would it take.
Depends on the tech, but the strategy rely on exponential local manufacturing.
If a factory could be copied in a day, then we would have a thousand of them 10 days later, and be able to produce a thousand tanks every day from then on.

If it takes 2 days, then it's 20 days till a 1000 factories.
20 days is probably a limit - three weeks is time enough for the enemy to catch on to our strategy, gather up forces and brute-force us off the planet.

So, in an optimistic scenario we need to hold ground for a week, after which our forces would start growing rapidly.

Big bottleneck would be power supply - compact nuclear reactors are difficult to manufacture, so we might have to do with whatever we can bring with us. That puts an upper cap on the exponential growth, until we can secure a local oil well or something similar.

Can natural caves be used to hide hundreds of thousands of tons of equipment?
They can provide initial shelter against first counterstrike. After that we establish more active defence, or get enough time to dig in.

Depending on how durable the beachhead is to nuclear attack, how concentrated the forces are and the surrounding terrain, a few warheads might be enough to cause severe trouble.
Not as bad as it might sound - a 1 megatonne missile, like what can be expected from a sub, only have a really effective radius of about 500 metres against a military-grade target.

So, 60 missiles would only cover an area 8 by 8 kilometres.

We would have 3 or 4 landing sites, each would produce several decoys, and split into two real groups - that plus ABM really diminishes the amount of nukes per real target.

#### fsci123

##### Future Dubstar and Rocketkid
I did not assume so originally, but even if there was considerable transport between the two planets, how would one smuggle a considerable amount of military hardware there? Performing a modern invasion, covertly (even only in part), seems impossible enough between nations on Earth- how would one do it between planets?

You could smuggle a small warship or at least several nukes in the payload bay of an earth-Venus cycler. I doubt the first strike has to involve landing soldiers the first strike could knock out sats and military bases.

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