Tutorial:RemoteTech2
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 the KSC.
Contents
Specifications
- Length: 45 minutes for "First Steps"
- 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 v1.3.3 and higher or Remote Tech 1.5 or 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 have far greater range, but must be targeted at a receiver. 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 via other probes. A ship must have a probe core to relay a signal. Mission Control has a special omnidirectional antenna with around 75 Mm range, but it still only works with line of sight from the KSC.
Antennae Specification Table
| Manufacturer | Model | Type | Range | Uses |
|---|---|---|---|---|
| Reflectron | DP-10 | Omni | .5Mm | Atmospheric flight within uplink range, terrestrial links, short range drone comms, relay network and vehical comms for smaller-than-Kerbin celestial objects |
| Communotron | 16 | Omni | 2.5Mm | Initial Kerbin relay network, LKO vehicles |
| CommTech | EXP-VR-2T | Omni | 3Mm | Relay network for non-giant celestial objects, KEO uplink; straight upgrade to to 16 |
| Communotron | 32 | Omni | 5Mm | High Kerbin space vehicles, KEO relay network, luxury omnidirectional coverage |
| Comms | DTS-M1 | Directional | 50Mm | Lightweight planetary system comms(Kerbin-Minmus reach), Jool relay network |
| Reflectron | KR-7 | Directional | 90Mm | Atmospheric flight within downlink range, planetary system comms(Kerbin SOI reach) |
| Communotron | 88-88 | Directional | 40Gm | Lightweight interplanetary comms(Kerbin-Duna reach), Solar relay network |
| Reflectron | KR-14 | Directional | 60Gm | Atmospheric interplanetary comms(Kerbin-Dres reach) |
| CommTech | 1 | Directional | 350Gm | Atmospheric Solar system wide comms |
| Reflectron | GX-120 | Directional | 400Gm | Luxury lightweight Solar system wide comms |
Kerbin Satellite Network Maximal Altitude Table
The following table shows the maximal and minimal altitude for a given set of satellite rigged with a specific type of antenna for interlink purposes on a Kerbin equatorial orbit.
| Interlink Antenna | 3 sat. | 4 sat. | 5 sat. | 6 sat. | 7 sat. | Comment |
|---|---|---|---|---|---|---|
| (Minimal Altitude) | 600km | 249km | 142km | 93km | 70km | Caused by Kerbin Geometry |
| Communotron 16 | 843km | 1,167km | 1,526km | 1,900km | 2,280km | 3-sat-sys. of this is the cheapest option overall |
| CommTech EXP-VR-2T | 1,132km | 1,521km | 1,951km | 2,400km | 2,857km | Can be used as a KEO uplink receiver along with outbound dish antenna to conserve power. |
| Communotron 32 | 2,286km | 2,935km | 3,653km | 4,400km | 5,000km | Can make a 3-sat-KEO network (coincidentally the cheapest KEO network) |
| Comms DTS-M1 | 28,267km | 34,755km | 41,932km | 49,400km | 50,000km | If the one hour night time is not an issue, the 3-sat-sys. of this can grant full Mun coverage with additional DTS-M1 as outbound antennae. |
| Reflectron KR-7 | 51,361km | 63,039km | 75,000km | 75,000km | 75,000km | Being heavier than the DTS-M1 the KR-7 is actually ill-suited for interlink purposes |
Note that a KEO-2-satellite-system is plausible, but will have some blind spots near Kerbin surface.
Also note that the DP-10 can theoretically form a network as well, but it will require 9-13 satellites near LKO.
Finally, the Communotron 88-88, Reflectron KR-14, CommTech 1, and Reflectron GX-120 severely out-range the KSC tracking station (75Mm), so using them as the interlink antenna of a first layer relay network would be a tad unhinged.
First Steps
The first antenna we'll get is the Communotron 16, henceforth referred to as the C-16 for brevity, and is acquired upon researching Engineering 101(2nd tier topic). The C-16 is omnidirectional, meaning it does not need to be pointed at any direction to connect. This is useful for 2 reasons: one, this means a single C-16 can connect multiple signals with ease; and two, with less power cost per connection. The C-16 however does have a very limited ranged of 2,500km, or 2.5Mm. The C-16 will also snap under dynamic pressure, making it ill-suited for launching or landing purposes.
Prior to any additional research, the C-16's only use at this point is to transfer scientific data nearby back to KSC. Which could speed up science gain if used properly.
The next available antennae are the Reflectron DP-10, unlocked by Flight control(4th tier topic); and the Comms DTS-M1, unlocked by Basic Science(another 4th tier topic), along with Stayputnik Mk. 1, the first available probe core.
The DP-10 is also omnidirectional, but has a even more limited range of 500km. However, the DP-10 is built to withstand dynamic pressure, making it perfect for launching and landing purposes. In fact, due to this, the DP-10 is activated by default for convenience! Finally, the power cost for DP-10 is negligible, so we can feel free to just leave it on.
The DTS-M1 is the first available dish antenna, meaning to be used effectively they will need to be directed at a celestial body or craft. Dish antennae also consume power more rapidly, meaning power management will be a serious concern with them. On the other hand, dish antennae has a much greater range when compared with omnidirectional ones, making them a must for missions beyond keostationary orbit. The DTS-M1 specifically, has a range of 50Mm, capable of reaching Minmus.
With the C-16, DP-10, and DTS-M1, we can now build a fully functional, fully unkerballed satellite network whose signal could reach Minmus. However, those satellites won't last very long, as we likely have no access to any solar panels yet, meaning the satellites can only last as long as the amount of their Z-100 batteries allow.
This means, the player is advised to only consider making communication satellites once they have gotten the Electrics topic unlocked(tier 5)...
Relay Satellites
Once the Electrics topic is unlocked, the OX-STAT Photovoltaic Panels will now be available, a far superior option to stuffing our satellites with batteries, which will still run down quite quickly powering several antennae. On a positive side note, this will also unlock the Reflectron KR-7 dish, which has even more range than the DTS-M1 and isn't as fragile, so we can switch it on on the launch pad. More importantly, once our relay network is up, the KR-7 will grant control to a probe during Kerbin landing, without the need of precision landing near KSC, unlike the DP-10.
With 4 antennae at our disposal and the knowledge of power generation, we can finally start with our satellite network! Our aim here is to put at least 3 relay satellites in Kerbin orbit so that we can bounce the signal from the KSC to anywhere around Kerbin, and, if we are feeling ambitious, to the Mun and Minmus.
We'll want our satellites to have the following 5 capabilities, in addition to a rocket able to reach the designated orbit:
- Control during launch. This can be a launch worthy antenna such as DP-10 or KR-7(initial uplink), or alternatively a kerballed lower stage, which will allow a level one pilot to execute prograde/retrograde hold. KR-7 is only recommended here if it also acts as an outbound antenna. But it's hard to go wrong with DP-10 here.
- Connection to KSC in orbit(orbital uplink). Here, all 4 antenna could be viable, depending on the orbital altitude of course, but the most power conserving option is the humble C-16.
- Connection among the network(interlink). Again, all 4 antenna could do if the height is right. But a omnidirectional antenna will be very economical here, power wise. This is especially true if the omnidirectional antenna also covers the previous item. So the C-16 gets another recommendation here.
- Connection to desired locations(downlink). Unless we are content with mere Kerbin coverage, we will want either/both of the dish antenna for the job. DTS-M1 has a shorter reach but lighter, whereas KR-7 has almost double the range but weighs half a tonne, on top of being not very aerodynamic. Although both takes the same amount of power. So the decision here depends upon our delta-v budget and desired reach.
- Enough power generation and storage. The night time of a given orbit needs to be consider here, the higher the orbit, the longer the night.
The possibilities here are endless, we could build a very economical 3 satellite network that uses C-16 for KSC and network connection, plus one or more dish antenna(e) each for further relays, at an altitude between 600km and 843km. Alternatively, we could--if power demand is not an issue-- use the dish antenna instead and build a network at keostationary orbit.
Here's an example of the latter if you get stuck:
An upper stage of two FL-T400 Fuel Tanks attached to an LV-909 Liquid Fuel Engine. A middle stage of two FL-T400s attached to an LV-T30 Liquid Fuel Engine and the first stage consisting of 6 FL-T400/LV-T30s attached with TT-38K 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 at least one KR-7. This rocket will just about reach KEO with a well executed ascent through the atmosphere, though a lower orbit will do.
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 make sure you get in to a stable parking orbit before then, or burn immediately for your target altitude, which should keep you more or less above the KSC. Circularise its orbit and that satellite is done for now.
Launch your second satellite to the same altitude and 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 and activate it to make the link bidirectional. If your second satellite ends up close to your first, then you can leave its periapsis a little low when circularising 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 to finish circularising your orbit. The most important thing is to get the satellites at matching altitudes, otherwise they'll drift relative to each other.
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!
Finally, switch to each of your satellites and target one of their KR-7s to Active Vessel and activate it. This will automatically keep one of their dishes targeted at whichever ship you're currently controlling.
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 and point them at your relay satellites and activate. Your relay satellites will already target one of their KR-7s at your probe because you set it up to target your active vessel. 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're doing your first Mun probe 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 two ways:
- Perform any actions required for landing, such as opening chutes and deploying landing legs in the upper atmosphere. KSP doesn't simulate reentry heating, so your parachutes won't be destroyed.
- Re-enter within 500 km of the KSC. This will allow your DP-10 antenna to link with the KSC and keep control of the probe.
While your probe to the Mun will likely only have 0.1s or so signal delay, a probe around Minmus can easily end up with around 0.5s signal delay, which is enough to become noticeable. Be careful when landing or docking when that far out, because fine control movements can be difficult.
If you want perfect coverage around Kerbin, including behind the Mun and Minmus, you can launch a further set of satellites out beyond their orbit, which will allow you to bounce a signal out and back behind them, or deploy a set of satellites around the Mun and Minmus like you did around Kerbin.
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 60 Gm range. The KR-14 can reliably reach Moho, Eve and Duna 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 350 Gm+ ranges. Remember links need to be bidirectional, so you'll need the strong antenna on the probe you send AND launch some satellites in to Kerbin orbit with the strong antenna on them to relay between the probe and the KSC.
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, which comes with every probe core and can be accessed with the calculator icon next to the signal delay display. The simplest way to execute a burn with the flight computer is to create a maneuver node with the maneuver you want, 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 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. Signal delay affects most operations on your probe, such as using science instruments, ejecting a stage, extending solar panels, etc. If something doesn't seem to have worked, check the flight computer to see if your command has been delayed.
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.
Landing probes on a planet with minutes of signal delay can be extremely difficult. Planets and moons with atmospheres are easier because you can use parachutes for the final descent, making control inputs unnecessary, or at least less important. Remember to take in to account the time delay of the command to open your chutes. Landing on planets and moons without atmospheres is likely to be an exercise in frustration, but killing your surface horizontal velocity and instructing your flight computer to hold the spacecraft directly up while applying a constant burn to slow your descent may work.
Remote Mission Control
Once you unlock the Large Probes topic you'll get access to the RC-L01 Remote Guidance Unit. This probe core is special because it contains a Command signal processor, which allows a ship equipped with it to act as remote Mission Control to any probes connected to it, however to do this the ship must also be crewed by 6 or more Kerbals. The main advantage of this is that a command ship can control probes near it with very little signal delay, even if far from Kerbin. Note that transmitting science results back to Kerbin still requires a link to the KSC.
