Project ZTC Tortoise Lunar Capsule

[Grover]

i agree, its managed to get everything you need into one vessel (even if it is two parts)
it took 4 different modules to make the Apollo stack (CM, SM LEM AS and LEM DS) and this has halved that in just the lamptrey and the tortoise.

an awesome idea, and whats better, it seems to be feesable as well! (though im sure NASA would pick holes... along the lines of budget... and how Obama can get out of the white house for all they care)

 

[Donamy]

I like the design too, but if it is built in orbit, I really don't see the need for retractable landing gear.

 

[K_Jameson]

Just because it's strange doesn't mean it won't work. After all, when designed properly, form follows function.
I think that it is a beautifully simple design, ideal for it's task.

My words weren't a criticism.

 

[Grover]

I like the design too, but if it is built in orbit, I really don't see the need for retractable landing gear.

the landing gear is built into the same part of the craft that re-enters the atmosphere, so if its not retractable, it would only melt at re-entry

 

[n0mad23]

@K_Jameson - I didn't take it as a criticism, but rather as a statement of fact. It is a very strange design, and actually much closer to my written fictional descriptions than I thought it would come out.

In my story, ZTC Ltd. is founded by dot-commers, gaming industry magnates, and a couple of sci-fi authors. Aerospace engineers are contracted to make sure the ideas work - so there's a deliberate attempt to do things a bit non-traditionally.

The system I'm working on is an INTERMEDIATE stage, and the Lamprey Engines Module (heheh - yup it's the TLC-LEM unit) is actually a work around to allow the Tortoise Lunar Capsule the ability to do some lunar exploration without a second tether-sling waiting for orbital capture at the Moon. The Tortoise is designed for stays on the lunar surface for up to 2 months.

@ Donamy - The Landing Legs are retractable because the Tortoise is dependent on aerocapture for its return to the Earth.

I think it might be wise for me to post the system in a linear-pictorial narrative fashion to explain how it all works.

1 - in an eccentric orbit around the Earth is ZTC-Ltd.'s Ananke Tether-Sling, a 120 km trebuchet. First the Lamprey rendezvous' with the Ananke at 250 km and after capture is accelerated by the rotation and tossed towards the Moon.

In my current rough tests (the Ananke hasn't been fine tuned for the Lamprey and should do much better after configured correctly), the Lamprey only needs an additional 327 m/s dV. The energy lost by the Ananke is recovered through a series of reeling and unreeling the lines over the course of 40 to 60 days (imagine how a ice skater accelerates a spin by pulling arms in close to body). The Lamprey uses its engines to create a parking orbit around the Moon.

2 - The Tortoise Lunar Capsule, considerably lighter than the Lamprey, only needs an additional 14 m/s dV to get to the Moon after being accelerated by the Ananke. Four days (aprox.) later, the Tortoise gets into a lunar parking orbit and then rendezvous' with the Lamprey.

3 - After docking with the Lamprey, the Tortoise relies completely on the "strap-on" for plane changes, descent and landing. Then again, the Lamprey is used to launch and create another lunar orbit. In several tests, I've gotten about a 50% plane alignment change as well (going from a circumpolar orbit back towards a equatorial one). Leaving just enough fuel in the Lamprey to do orbital adjustments (in scenarios where fuel tugs are sent to resupply the Lamprey) or perform a de-orbit burn.

Unfortunately, I don't have the Tortoise animations done (and am dreading them), so I can't show you all the landing configuration yet.

4 - The Tortoise has sufficient power and fuel to then head back to Earth. In the last picture of this sequence is aerobraking at around 75 km. In my rough tests, I've found setting the PeA to between 70 and 75 km results in a 2 km/s dV loss and a resulting orbit with the ApA at around 900 km.

The Tortoise aerobraking over Congo. No flame out, but I find the image of the Tortoise in hypersonic flight to be a grand one.

Thanks so much for the comments gang! Doing this kind of work is so much more rewarding when I don't feel like I'm shouting into a vacuum.

 

[Mandella]

The energy lost by the Ananke is recovered through a series of reeling and unreeling the lines over the course of 40 to 60 days (imagine how a ice skater accelerates a spin by pulling arms in close to body).

I never managed to put away the time to play with the first version of the tether sling, but I am certainly going to make the time for this!

I do have a question though. I understand how spin can be accelerated an decelerated by the "ice skater effect," but don't you still lose total angular momentum? In other words, unless the tether is gaining the energy back by capturing the capsule on its way home (which it is not), there has to be some way to return angular momentum.

That said, I can think of more than one way off the top of my head. Solar powered low thrust ion engines, or something more esoteric with magnetic induction.

Or am I just completely misunderstanding the Ananke design?

 

[n0mad23]

I never managed to put away the time to play with the first version of the tether sling, but I am certainly going to make the time for this!

I do have a question though. I understand how spin can be accelerated an decelerated by the "ice skater effect," but don't you still lose total angular momentum? In other words, unless the tether is gaining the energy back by capturing the capsule on its way home (which it is not), there has to be some way to return angular momentum.

That said, I can think of more than one way off the top of my head. Solar powered low thrust ion engines, or something more esoteric with magnetic induction.

Or am I just completely misunderstanding the Ananke design?

Originally I imagined re-energizing the system using ion or plasma thrusters, but energy is energy and it's entirely possible to transfer rotational energy into angular energy. Yes indeed - I was really surprised to learn this, too. However, upon reflection it makes a lot of sense and it's all a question of where reconfiguration is done in the orbital cycle.

From the 3rd Ed. of "Tethers in Space Handbook":

The achievable orbit change scales with the tether length (as long as delta r << r). Retrograde libration releases are inefficient, but allow concentric orbits. Apogee & perigee boosts have different values in different applications. Tethered capture can be seen as a time-reversal of a tether release operation.

Tethers merely redistribute angular momentum; they do not create it. Changes in tether length, libration, and spin all redistribute momentum. Momentum transfer out-of-plane or in deep space is possible but awkward

Reeling/unreeling can be done either as "libration pumping" or "spin pumping." If you imagine a tether-sling shortening its length while climbing up the gravity well towards its ApA, you can begin to see how the orbit shrinks. Conversely, unreeling while accelerating towards PeA can increase the orbital radius. However, the "professionals" who actually studied this added an electromagnetic component that's even better!

I was "gifted" a really nice package of related technical reports from someone in the Advanced Technologies Dept. at NASA and will search for and post links in the Space Research PDF thread soon.

Besides finding out about this neat trick involving reeling and unreeling cables, the NASA designs also used anodes and cathodes at each end of the design, and fed electricity down aluminum wires and effectively turned the tether-sling into an electro-magnet that is repelled by the Earth's magnetosphere. The electricity to be supplied from solar panels at each section of the tether spools, which I replicated with the Ananke. This is incorporated into the Ananke (theoretically) as well. I'm drawing from memory, and suspect tblaxland's too busy to respond, but I remember him saying his calculations in tossing the stock DG has the Ananke's angular velocity recharged in 40 days only using a combination of reeling and magnetic repulsion. NASAs theoretical project was called MXER (Momentum Exchange/Electrodynamic Reboost) as the magnetic component was the main seller of a system that really required two vectors (a catcher that becomes a receiver) to continually reboost the systems energy.

The electrodynamic reboost and reeling capabilities were never incorporated into the Ananke.

I'm still really attracted to the possibility of a cislunar tether-sling transportation network, but honestly it's way outside my mathematical skills. Jarmo Nikkanen, author of IMFD, might be able to pull it off but I can't think of too many others. It's mind boggling contemplating a spinning tether tip in LEO doing over 8 km/sec, and even more mind boggling considering an intercept with another tether tip 4 days later in LLO.

 

[n0mad23]

I think I have the Tortoise Lunar Capsule's mesh pretty much done. There's still a few final adjustments to be made (fine tuning the alignment of the support cage, making sure the windows line up perfectly), and I need to rethink the cockpit.

The prototype's got a name, too. She's the "Lyra" for obvious mythological reasons. I've retained the two solar panel arrays, but dropped all but one of the radiators as it's got sufficient area to cover the living quarters needs. It unfolds upwards into 4 panels. Beneath the stowed radiator and communications dish, the Common Room windows are shielded. When the radiator and dish rotate into use, the craft's kitchen area is clearly seen.

Here, Alberto Bean is seen piloting the Lyra in LEO. Sitting beside him is Avril Scotland, the co-pilot and chief science officer. The 3 panels at the bottom open up to reveal the docking neck.

The TLC in cruising orientation. The bottom shield couples as a solar shield, and the solar panels and communications dish rotate away from the craft for maximum exposure.

I'm contemplating doing a SC3 VC with the Lyra. Even with the limitations, I think it'll really enhance the lunar landing experience.

 

[MaverickSawyer]

:drool:




damn... didn't work.
Oh well, :10sign::11sign::bananadance:
I want that!

 

[n0mad23]

I've done several exports and mesh conversions, and think I finally have the Tortoise set within +/- .01 m on the Y axis where it needs to be. This is important as when the legs are extended, their landing point has to be in agreement with the Lamprey's landing position. Now I'm settling in to Mesh Wizard and consolidating groups so I have a manageable mesh to begin the animation processes.

First up will be the landing legs (and shield-doors). Then I'll do the docking neck and doors and the cargo bay doors at the same time. Then it's off to the 2 solar panels and the radiator. The final (as it's least significant) will be the communications dish.

I thought I was totally done with the Lamprey (in terms of modeling and animations) but I've forgotten something really important. Where's the ladder for lunar EVAs? :facepalm: Looks like I've got to go back to Anim8or one more time with the LEM, and then re-consolidate the groups to get the animations back together. The ladder will require another bit of animation, too. I've always planned on installing it on the forward most rocket assembly, right in front of the docking doors.

I think I'll make a beta-test available when I've got the landing legs done.

Sound good, or should I get all the animations done first?

 

[MaverickSawyer]

Get the beta out ASAP, n0mad. That way, you can figure out how it will handle first. I can provide some abusive testing.
(for the computer, not the tortise/lamprey...)

 

[n0mad23]

Oiy! Close to 500 groups in the Tortoise mesh. I spent about 2 hours cleaning up the first 40 wonky groups (textures misapplied to an end of a tube, single vertices without assigned texture, etc.) only to find that I'd neglected to ungroup my solar panels! Grrrrrr. The only good news about that is in having to re-export the model from Anim8or I actually remembered to add the lights over the docking bay and cargo bay doors.

My astronut models (not to be confused with astronauts, as the ZTC crew are nuts) are official. I got a email from Max Gruter (author of outstanding sketchup models) giving me permission to use his work in the project this morning.

So it's back to Mesh Wizard for me, and hopefully in the next few days I'll have a beta available with working landing legs, and another export of the Lamprey with a working ladder so the nuts can actually get up and down from the lunar soil.

 

[MaverickSawyer]

Any idea as to the size of the file?

 

[n0mad23]

At this point the Tortoise's mesh is just over 8 megs, and the Lamprey a little over 2.5 megs, and there are around 50 textures as well. It all packs up nice and tight with 7zip, and the entire package will be about a 4 meg. dl.

I'm doing this on a dual-core laptop with a Nvida chipset and still pulling over 60 fps, even with both models loaded and connected with Universal Cargo Decks. I don't think the mesh size will cause anyone problems, unless they're on a really old machine (mine's 4 years old all ready).

 

[n0mad23]

I've had a bit of a delay with the latest rounds of 3ds - msh exports. For some reason, Anim8or stripped all the textures from the Tortoise cockpit and I've had to retexture everything. In some ways this was a good thing as it made me do the blank MFD panels that I'd been putting off for a SC3 VC.

Many hours of carefully putting the dome shell and tubular exoskeleton back together, and it's finally ready to clean up and optimize in Mesh Wizard. I've got my notebook sitting beside my chair for writing animation groups into. My youngest just gave me a Smens Pen that's mocha scented, and I think I'll use that to replicate the ZTC culture.

I took a bit of time over the weekend to do a couple more test flights and play with possible optional MFDs. I've found computerex's AutoHover MFD to be quite useful for the final lunar landing sequence, as well as the possible "optimal" altitude for the final landing approach. The TLC-LEM system is a bit sluggish, and a 3.5 to 4 km orbit seems to work best for me so far. I think dropping it to 2.5 to 3 km would be better in terms of the fuel supply, but it'll take some practice. The Lunar Transfer MFD I think I'll list as "required" as its by far the best one for plotting the Tortoises return trip. Though I usually prefer to fly-by-wire while aerobraking, the AerobrakeMFD will be highly recommended, too.

Hope to have a beta up soon.