Folding Fido

In my recently posted "Driving Duna" adventure (where I drove a rover all the way around Duna), one person commented on my photo of the Fido rover sitting on top of its rocket. He was rather displeased that Kerbal Space Program lets you get away with ignoring aerodynamics, and just slapping MOAR BOOSTERS onto something (like my rover with its big "heat shield" plate) and pushing it into space. For the record, he was not complaining about my mission in particular, just in the lack of proper aerodynamics in KSP. The offending image is shown below.

My first thought was, "What must this guy think of the monstrosities used to loft those huge rovers with the giant wheels?" My second thought was, "Don't I at least get points for bothering to include a "heat shield" in anticipation of the time when we will all face the perils of deadly reentry heat?" My belated third thought was, "Well...he has a point..... so how do we go about fixing it?" I wanted the wide wheelbase for the Fido so that it would be very stable and safe for kerbals to drive at high speeds across alien landscapes ( KNOW they are going to). So how could I get my wide rover into a smaller living space? By folding it! NASA does this sort of thing all the time. But how to unfold a folded rover? I used the cool Damned Robotics mod. Specifically, the "door hinge" part from that mod pack.

Below is my folded Fido rover with its "heat shield," sky crane lander, and token nose cone. I didn't actually make an aerodynamic shroud for the thing (you can just picture that running from the base of the nose cone to the heat shield. And you can picture the heat shield as nice and round with an ablative coating (instead of something I kludged together from plate structural parts).

First lets get rid of the nose cone. A decoupler and two sepatrons take care of that. You can picture the aerodynamic shroud that you were picturing splitting in half and blowing away, too (you didn't know this thread would involve all this reader participation, did you?). One of the sepatrons is canted sideways by one tick to make sure the nose cone gets out of the way of the rest of the vehicle (it crashed about 500 meters away).

The animated GIF below shows the two sides of the Fido unfolding. I have this action of the hinges controlled by the 0 key (Damned Robotics's little control panel lets you specify what keys to use for a hinge or group of hinges in the VAB). The rover actually appears on the launch pad unfolded, so I needed to fold it up before showing it off or launching it (using the 7 and 9 keys).

Below, four more hinges are called into action with the 8 key to swing out the wheel mounting plates. You must press the key several times for full deployment, since the hinge can be positioned at intermediate positions.

Below is the Folding Fido rover with its wheels fully deployed. The wide wheelbase of my dreams is realized from a more compact package!

You may have noticed that the exhaust blast from the sky crane's engines would impinge on the rover when it is fully deployed...this is true. So the sides of the rover can only be partly deployed under the operating sky crane. Below you can see the sky crane hovering the Fido over the KSC during a test flight. Sure, you could mount the sky crane engines further out to prevent this, but I wanted a sky crane that would fit inside the imaginary aerodynamic shroud, and which would also be protected by the heat shield during reentry. So I'll live with this partial-deployment limitation.

In the next picture, I've dropped the heat shield so I can set the Fido down with the sky crane. I also deployed the wheel mounting end plates fully before dropping the heat shield.

After the Fido is set down in its partially-deployed condition, and the sky crane has flown off, the side pieces of the Fido can be deployed the rest of the way. Note that you do not have to deploy the sides completely: If you are going to be driving over some rough terrain, you can dial in a higher ground clearance (at the expense of a little narrower wheelbase).

Below are two pictures of the fully-unfolded Folding Fido. I was worried that the hinges might not be very strong and the whole thing would just flop to the ground, but the hinges are quite sturdy. You can see them flexing a little when the rover hits bumps, but I was pleased with how well they held the rover in its shape. The Fido is very stable and corners well at speeds of 23 m/s (with its ASAS on). Hmmm...I should have deployed the ladder (it's in the nose of the capsule). And I see that I forgot to remove two of the solar panels from the center plate on the right side (where they would be susceptible to damage by the engine blast...I removed the two on the left side). The Fido has four RTGs and two of the Z-500 battery banks, so it can drive some distance even in the dark (but would need to stop and rest occasionally). The Fido has a couple strategically placed small I-beam pieces on the underside to protect the more fragile parts if the rover gets bonked on the bottom.

Below we see the Folding Fido payload on top of a unnecessarily powerful booster that could probably send it most anywhere in the Kerbin solar system with its nuclear transfer stage. I've already folded up the rover so you can picture the nice aerodynamic shroud enclosing it. Go ahead. Picture it. Smooth. Nice curves. Oh yeah.

For those of you who couldn't bother to play along, below is the "5,000 hours in MS Paint" version.

I haven't sent the Folding Fido on a mission to another celestial body yet, but I did try out reentering it into Kerbin's atmosphere. Below is the retro burn.

Here are two images of the reentry. All parts of the Fido and its sky crane lander are protected by the heat shield (as long as you keep the heat shield pointed in the retrograde direction). You don't get the blazing white-hotness of an Eve entry, but the heat shield is working well. You can imagine the smell of charred ablative material now if you are still playing along.

Below: dropping the heat shield. I hope everybody at the KSC in undercover, because a toasty-warm present is coming their way.

This is the point where I quickly deploy the side pieces to their partially-deployed angle, and swing the end wheel plates out all the way in preparation for landing.

The animated GIF shows the successful sky crane maneuver, followed by full deployment of the Fido.

I also included two parachutes on the Fido so that it could use the alternate landing sequence below on a body with a sufficiently thick atmosphere (Kerbin, Eve, Laythe... or Jool if you are nuts). In this alternate landing sequence, I separated the sky crane soon after jettisoning the heat shield...

...then popped out the two chutes and began full deployment of the wheels (in progress in the picture below).

Below, the Fido is coming down at about 7 m/s. It landed undamaged...but I think maybe two more parachutes (placed on the two plates attached to the central core) would be better.

Now I just need Kerbal Space Program to include the feature that lets me make any size and shape aerodynamic shroud, and I'll be all set. And a prettier heat shield, of course.


I landed the Folding Fido on Minmus to test it out. Its sky crane is ridiculously overpowered for Minmus... when I separated it after landing the rover, the sky crane spent many minutes thrusting at low power, very slowly tumbling, and it couldn't seem to decide if it wanted to end up in a high orbit around Kerbin, or escape into Kerbol orbit. In the end, it escaped. The Fido worked fine...and I could make it hop upward quite a ways just my partially folding in its wheels.

I made some modifications to the Fido to make the sky crane/heat shield/nose cone arrangement a little more compact and a bit lighter. Below is the modified version folded and unfolded. I also have the .craft file for the payload posted. It requires the Damed Robotics Door Hinge part, and that requires that the MechJeb dll file be installed. The Fido has the hinges set to use the 7 key to fold in the wheel end plates (fold these in until the wheels are close will be a greater than 90 degree fold), and the 8 key to unfold the wheel end plates. The sides of the Fido are folded down with the 9 key (fold them in 90 degrees), and unfolded with the 0 key. You may not want to unfold the sides completely if you want better ground clearance (especially if you want to drive using physical time warp...the hinged Fido deforms downward MUCH more under high time warp than the unhinged Fido KE it's based on). Using 4x time warp will bottom out the Fido even if you have a lot of ground clearance set.

I made the heat shield less dish-shaped. It still has the same coverage, but it lets me mount the Fido closer to the heat shield. Below is a reentry from 1000 km for better reentry effects.

But the most important change was rotating the sky crane 90 degrees and repositioning the rear RTGs... Now the wheels can be fully deployed for landing under the sky crane.

Folding Fido .Craft File

Another Update

I modified the sky crane some more, making it more compact. The Fido rover has been modified to have two capsules in a "push-me-pull-you" configuration.

The sky crane has less fuel than before, but still sufficient to return the Fido from Kerbin orbit, so it can handle a landing on several other bodies.

Below, the sky crane deposits the Fido near the VAB and then heads off to crash. It's definitely a good idea to fold the sides of the Fido down a couple notches before landing since this gives it more ground clearance to survive a bounce if you drop it from a little higher than you should.