Antennae vs. Aerocapture?

[Geschosskopf]

For them as ain't experienced it yet, hitting any atmosphere (except Duna's) at interplanetary transfer speeds burns off antennae quite easily, even if they are retracted. This is a problem for folks who use RemoteTech (or AntennaRange with certain options enabled). The main payload probe going to Laythe, Eve, or wherever can be safely protected in a fairing that remains intact until after the aerocapture, but the ship as a whole still needs a long-range dish exposed on the outside for the trip out there, getting into orbit, and finally detaching the main probe. But if you lose that antenna during aerocapture, you're pretty much hosed. So, what's the best way to protect the "en-route" antenna?

I've considered several options, none of which I like.

1. Stay Out of Atmospheres

100% effective but requires carrying way more fuel and engine to capture via thrust alone, which increases mission costs.

2. Set for Less Reentry Heat

An across-the-board change made at the start of the game via the difficulty slider. Kerbin's heat already isn't a major issue anyway so you lose nothing there, and its easier to do other planets. Feels a bit shady but OTOH the issue is the rather bogus way 1.x handles heat and atmospheric density, so can be considered a necessary fix.

3. Cheats

Use ModuleManager to increase the heat tolerance of antenna, or use the debug window to ignore maxTemp. Definitely shady but again, the underlying system is inherently flawed so.....

4. Robotic Antenna

Rig up a cargo bay or service bay with some Infernal Robotics parts that enable you to pull the antenna inside and close the door behind it. Adds ship complexity and part count, the necessity for another large mod, and makes the rocket heavier and more expensive. Also requires kOS to deploy the antenna again after aerocapture and kOS seems to have difficulty with working IR parts.

5. Sacrificial Antennae

You let the original exposed antenna burn off and have a 2nd (and maybe 3rd and 4th) "en route" antenna under a small interstage fairing that you deploy after an aerocapture pass. Still need kOS to pop the interstage fairing(s) but at least there's no need for IR. Also, more mass, complexity, and part count, especially if you're going to bounce off Jool to hit Laythe or use multiple aerobraking passes after the 1st aerocapture.

Anybody got a better idea?

[Brainlord Mesomorph]

Stock payload bays?

Someone could invent a non-stock part, an antenna in a case. Like the solar panels.

[Dilli]

Can angel of attack during the aerocapture not be used to shield parts? (I recall only heating / loosing items on one side a craft when entering at steep angels of attack)

[Warzouz]

I've put an antenna in a stock bay once. The antenna would deploy inside the ship. It works correctly. I didn't test the aerocapture though.

[stibbons]

Action groups.

* Assign an action group that extends your solar panels and antenna. Doing this is a good idea anyway, just because extending everything at the same time is cool.

* When you're a little way out from entering the atmosphere, set a manual delay on your remotetech flight computer for far enough in the future that you know you'll be back out of the atmosphere.

* Hit your extend-everything action group key. The flight computer should now show that it's going to execute that action group at the given time.

* Don't forget to set the manual delay on your flight computer back to 0, or you may end up having a bad day.

* Make sure your flight computer is aligning your vessel in the right direction.

* Close solar panels, then shut down your antenna.

The first time I did this was a nail-biting experience. But you should find yourself skimming through the atmosphere, and have the action group execute and extend your antenna and bring your probe back online when it's a safely back in vacuum.

EDIT: I'm sure this technique used to be documented in the RemoteTech manual, but I can't seem to find it now. Hrmn.

Edited June 18, 2015 by stibbons

[Streetwind]

6. Carry an aerocapture shield. You can have exposed parts behind the shield, so long as they don't stick out into the airstream. That's the same effect that protects parts stuck to the sides of a command pod when it performs reentry - the heat shielded base is wider than the top. So depending on how you build your ship, you might be able to even shield large dishes. (And if not, get creative... carry a small omnidirectional antenna that's easy to hide behind your shield but decouple your large dish with a probe core and another omni so that it doesn't hit the atmosphere. You can then unfold a spare dish after you finish aerobraking but before your sacrificial dish is out of range. Or heck, if you're exploring a new body, you want to carry commsats there anyway, so make your sacrificial dish a fully fledged sat that brakes propulsively into orbit while you aerocapture.)

7. Can't the RemoteTech flight computer buffer commands? Maybe it can be commanded to toggle the antenna with a delay of 10 minutes or something. It's been quite a while since I last played with RT, but I did find the flight computer quite useful...

EDIT: Hah, ninja'd on the flight computer. I knew it.

Edited June 18, 2015 by Streetwind

[Old Foxboy]

Put all Parts that can explode behind shields, doors, fairings and behind the airstream. That's how they do it in real life, too, i guess, maybe, probably.

[monstah]

5. Sacrificial Antennae

You let the original exposed antenna burn off and have a 2nd (and maybe 3rd and 4th) "en route" antenna under a small interstage fairing that you deploy after an aerocapture pass. Still need kOS to pop the interstage fairing(s) but at least there's no need for IR.

You don't need kOS; open up RT's flight computer, set a delay to a couple of minutes. Click to activate the 2nd antenna, then disable the delay. The activate action is on a countdown now!

- - - Updated - - -

I have "toggle antenna" on my action groups so I can do that with only one antenna: put delay, hit toggle. disable delay, hit toggle again. You're out of communication for some time, so you have to set everything beforehand and hope you forgot nothing

[A_name]

I second the stock service bay and angling your craft to shield the antenna from reentry heat.

[Geschosskopf]

The first time I did this was a nail-biting experience. But you should find yourself skimming through the atmosphere, and have the action group execute and extend your antenna and bring your probe back online when it's a safely back in vacuum.

Sure, that's the theory, but it doesn't answer the question of how to protect the antenna during the atmospheric pass. The stock 88-88 antenna can fold up but it still burns off the outside of the ship even when folded, and the RT dishes can't fold. So you need some thing that brings them inside a cargo bay.

Seriously, why bother animating an antenna (or a ladder, for that matter) if it's folded state confers no game benefits? They should be like retracted landing gear with little or no drag when folded and largely safe from heat. Sounds like a job for Stock Bug Fixes.

6. Carry an aerocapture shield. You can have exposed parts behind the shield, so long as they don't stick out into the airstream. That's the same effect that protects parts stuck to the sides of a command pod when it performs reentry - the heat shielded base is wider than the top.

This is a good idea in some cases. It does, however, have to overcome one of the problems with the heat system, which is that during a reentry, the parts at the trailing end of the craft get hotter than those at the leading end. You can demonstrate this by taking an orange tank and sticking a Sr. docking port on 1 end and others radially attached on the sides. The port on the end, exposed to the full brunt of reentry, will survive a pass that burns off the identical radial ports. So the shield has to be wide enough to account for this.

And that's complicated by the aerodynamic effects of any fairing over the main payload probe. If this has any length to it, it will (thanks to how body lift is figured) make the ship hold a bothersome angle of attack (like 10-15^) instead of weathervaning pure retrograde. Thus, the benefits of the shield are lost except within a short distance of where the shield is attached, perhaps too close to allow the dish to open without clipping.

[Psycix]

In the case of remotetech, retracting the antenna makes sure it can be used in atmospheric flight. Not re-entry, but at least it can survive flight, just like stowed solarpanels versus expanded ones.

[Prepper-Jack]

The 500km omni antennas are fairly resilient (the always-on antenna). If you drop a 5Mm omni, coupled with a long range dish in low orbit, it should be enough to get to the surface and unpack a real dish/omni.