Difference between revisions of "Tutorial:RemoteTech2"

Revision as of 15:59, 18 February 2014

RemoteTech 2 is a mod for KSP that modifies how unmanned probes work. Specifically, any unmanned probe must have a control link back to the KSC (or to a command ship, more on them later), requiring you to set up a satellite network to maintain links with your probes. RemoteTech 2 also simulates communications delay when giving commands to probes - while pottering around Kerbin this is merely irritating at around half a second, but interplanetary missions are seriously complicated by the several minute delays, necessitating the use of remotely executed commands. Transmitting science reports from any spacecraft, even manned ones, also requires a communications link back to Mission Control.

Specifications

• Length: 30 minutes
• Difficulty: Advanced - This tutorial will assume you can already get a rocket in to orbit without Remote Tech 2 and are familiar with basic orbital mechanics.
• For version: KSP 0.23 and higher and RemoteTech 2 (not 1) v1.3.3 and higher.

Antennae and links

There are two main types of antenna - omnidirectional and dish. Omnidirectional antennae can broadcast to any other antenna in range, but they typically have limited range compared to dishes. Dishes must be targeted at a receiver to work. Any link must be bidirectional and have unbroken line of sight to work. To keep control over a probe you must keep it connected to Mission Control, either directly or by being connected via other satellites. Mission Control has a special omnidirectional antenna with around 50Mm range, but it still only works with line of sight from the KSC.

First Steps

The first antenna you'll get is the Reflectron DP-10 that's unlocked at the same time as the Stayputnik probe core. The Reflectron is omnidirectional, is on by default (meaning you can control your probe on the launch pad) but only has a range of 500km. This means you'll only be able to control a probe with one of these until shortly before it goes over the horizon, even in a low orbit. You'll still want one on each probe, but to do much useful you'll need a second antenna.

The second antenna you'll find useful is the Communotron-16. It's an omnidirectional antenna with a range of 2.5Mm, so it can reach around Kerbin low orbit, but not quite to keosynchronous orbit. This antenna will break if deployed at speed in an atmosphere, so you'll still need a DP-10 to get in to orbit. The Communotron-16 is useful, but not as useful as the next antenna...

The third antenna you'll want to use is the Comms DTS-M1. This has 20 times the range of the Communotron-16 and can just about reach Minmus, but is a dish antenna, so it must be aimed to work. The DTS-M1 is fragile like the Communotron, so you'll need to wait until you're in space before deploying it.

So, the DTS-M1 has the range to reach the Mun, so we slap one on, connect it to the KSC and we're ready to go right? Unfortunately not. The KSC is only on one side of Kerbin, so when your probe is on the other side, it will lose its link with the KSC and you'll lose control of it. Only being able to control your probe half the time will be very problematic, so our first step is to set up a small set of satellites to bounce your signal from the KSC around Kerbin.

Relay Satellites

For this you'll at least need the Flight Control and Science Tech topics unlocked. The Electrics topic is also extremely useful, because it unlocks basic solar panels, which will be far superior to stuffing your satellites with batteries, which will still run down quite quickly powering several antennae. On the plus side, this will also unlock the Reflectron KR-7 dish, which has even more range than the DTS-M1 and isn't as fragile, so you can switch it on on the launch pad.

Here's an example relay satellite rocket:

An upper stage of two FLT-400s attached to an SV-909. A middle stage of two FLT-400s attached to an LVT-30 and the first stage consisting of 6 FLT-400/LVT-30s attached with radial decouplers. There are of course many other ways of designing this rocket, this is just an example if you get stuck. Note the single DP-10, 3 DTS-M1s and 3 KR-7s. This rocket will just about reach keosynchronous orbit with a well executed exit from the atmosphere, though a lower orbit will do. The important thing is to get the satellites at matching altitudes, otherwise they'll drift relative to each other.

Launch your first satellite over the KSC. As you leave the atmosphere, target one of your DTS-M1s at Mission Control and activate it. Remember you'll lose contact with the KSC if you go over the horizon, so your best bet is to burn immediately for your target altitude, which should keep you more or less above the KSC. Launch your second satellite to the same altitude then target one of its DTS-M1s at Mission Control, and a second at your first relay satellite and activate them. Switch to your first relay satellite and target one of its DTS-M1s at your second satellite to make the link bidirectional. If your second satellite ends up close to your first, then you can not quite circularise its orbit when burning at apoapsis; this will leave it with a slightly shorter orbital period than the first satellite, and it will move ahead of it a little each orbit. Once you're happy with its position relative to the first, burn again to finish circularising your orbit. Launch your third and final satellite, link it with the other two satellites (and them back to it) and mission control and place it in an orbit to make a triangle with the others. Hopefully your satellites now look something like this in the Tracking Station:

If so, congratulations, you've made your first set of relay satellites!

Next Steps

Now that you've got your first set of satellites equipped with KR-7s, you can control a probe almost anywhere in the Kerbin sphere of influence. Equip any probe with 3 KR-7s. Before launch, switch to your relays, target one of their KR-7s at your probe and activate, and target the probe's 3 KR-7s at the relay satellites and activate. Despite their appearance, KR-7s don't need to be physically faced towards the target. You should now be well set to send a probe to the Mun. There are still two places your communications network can't reach, and that's directly behind the Mun and Minmus, so make sure you plan your route so you don't need to make a burn when behind them. If you want to solve this problem you can launch a further set of satellites out to beyond the Mun and Minmus' orbit, which will allow you to bounce a signal out and back behind them, or set up a set of satellites around the Mun and Minmus like you did around Kerbin. Note that once you start bouncing a signal out to 60Mm and back the signal delay (displayed under the time warp and mission time display) will start becoming noticeable. This won't usually be a problem when doing basic orbital burns, but will make finer operations like docking and landing tricky, but still possible.

If you're doing your first Munshot without the Electrics topic unlocked then you'll be using DTS-M1 or Communotron-16s for your long range communications. This has the unfortunate problem that these antennae will burn up on reentry, causing you to lose control of your probe and be unable to open parachutes or fine tune your landing. You can solve this problem one of two ways:

• Perform any actions required for landing, such as opening chutes and deploying landing legs in the upper atmosphere. Stock KSP doesn't simulate reentry heating, so your parachutes won't be destroyed.
• Re-enter within 500km of the KSC. This will allow your DP-10 antenna to link with the KSC and keep control of the probe.

Going Interplanetary

Your KR-7s can talk to any satellite in Kerbin's sphere of influence, but they won't reach much beyond that. For that you'll need to unlock the Reflectron KR-14, with its 60Gm range. The KR-14 can reliably reach the inner planets and just about reach Dres, but it can't reliably reach Jool. To reach Jool and Eeloo you'll need to unlock the Reflectron GX-128 or CommTech-1 with massive 350Gm+ ranges.

Other than needing the more powerful antennae, once you send probes to interplanetary distances the signal delay will reach several minutes, making interactive control of your probe unfeasible. To make burns you'll need to use the Flight Computer. The simplest way to execute a burn with the flight computer is to create a maneuver node, instruct the computer to NODE, which will pre-orient the spacecraft in the burn direction of the next maneuver node, then EXEC, to schedule a burn of the correct length at (sort of) the correct time. By clicking the >> icon you can see the commands being sent to the probe and the time it'll take for them to get there.

Remember that you'll lose contact with your probe while on the far side of the planet from Kerbin. You can solve this problem by stationing a satellite in high orbit over your destination planet (either send it as a second craft or decouple it from your main craft) to bounce a signal off.