Flight of the Argonian

[Geschosskopf]

that X Rebirth has finally been released. I've been playing the X games since the get-go so I'm rather interested in this, even if it is a rather big change from the previous ones.

But anyway, in the X games, you character is usually an Argonian from Argon. And it just so happens that I have the Near Future mod with argon-burning engines. So, in honor of the release, I decided to build a ship with using the biggest VASIMR argon-burner in the mod, which I'd never used before, and see how far I could get with it.

The reason I'd never used the big VASIMR before is because to get full thrust (which is only about 90kN) it requires 10,000 electricity PER SECOND, ISYN! And there is nothing in the mod that remotely comes close to doing that by itself. What it does have is 3 sizes of fission reactors, the biggest of which produces a "measly" 2000 per second, so you need 5 of them, and they weigh 6 tons each. Still, that's the most power-to-weight of all the power sources in the mod. And in fact it turns you need a bit more juice than 10,000 per second, so I slapped on some of the mid-size reactors as well. And to fuel it, I made a huge asparagus array of the biggest argon tanks. This created a very long monstrosity so I used 4 of the largest size of RCS tanks I could find and also the triple-power RCS thrusters from Nova-Punch to turn the thing. And then I topped all this off with a 1-man capsule .

I all this "The Argonian". Behold:

Before you ask, HELL NO I didn't launch this from the ground, nor did I assemble it in space. I just HyperEdited it out to 40,000,000m from Kerbin, just inside Minmus. This is a project of pure silliness, not something I want to do "right" or whatever. I just want to see if the thing will work and how well, not be all serious about it. I've had enough of seriousness lately getting all my Jool armada hammered together and needed a break from all that.

So, I'm generating about 11,600 electric charge per second. I've got somewhat over 30,000m/s of fuel. And I've got a TWR of only 0.07, but which looks likely to improve to a healthy 0.12 by the end of the mission . All to carry 1 Kerbal (naturally Jeb). However, I think the real limiting factor will be RCS fuel. After seeing how much I spent orienting for my Duna departure, I figure I've only got enough RCS for about 10 burns.

Or maybe my patience will run out first.....

Here we see the mighty VASIMR running full power (it damn well better be with all that electricity) for the Duna ejection burn. Which at this distance from Kerbin is only 611m/s, yet still takes 15.5 minutes thanks to the pathetic TWR. Naturally, MJ is going to be doing the burns while I read a book . I think Jeb's going to be gone a LONG time.

I really wonder if I'll be able to stop at Duna. With thrust so low, it seems likely that a capture burn would last longer than my time in the SOI. We'll see. Worse comes to worst, I figure I'll have a go at achieving Kerbol-escape .

Anyway, the big VASIMR seems totally impractical, but what in KSP is practical?

[Tw1]

Aerobraking at Duna not an option?

[BlazeKerba]

I know you didn't want to do it but launching it from the launch pad while recorded for us to watch could be one of the most hilarious things of all...suppose we would wait

But DAAAAAAYUUUMMMMMM that vessel is rad. 1 command pod? I dunno if i want to be the Kerbal with that fat rocket/engine attached to me rear man...it freak the crud out of me o_o

[KSK]

Heh - a real tribute to the X games would have been powered by solar arrays (aka a solar power plant) and left on time acceleration overnight to get anywhere

That is one sweet looking ship anyway!

[Geschosskopf]

Aerobraking at Duna not an option?

Not really. The CoM is right about in the center of the ship to make it easier to turn the thing, which means it would have a very strong tendency to switch ends or go sideways during aerobraking. And I don't think it would survive that because the only struts in the whole ship brace the side tanks. Struts don't stick to the reactors which make up most of the length.

I know you didn't want to do it but launching it from the launch pad while recorded for us to watch could be one of the most hilarious things of all...suppose we would wait

I think the only good way of getting something like this off the ground is in pieces with assembly in orbit. You can't really build a cage lifter around it because nothing can attach radially to the reactors and the side tanks aren't themselves attached solidly enough to the core to take the strain.

Heh - a real tribute to the X games would have been powered by solar arrays (aka a solar power plant) and left on time acceleration overnight to get anywhere

It would definitely need to be overnight using solar on this thing. The biggest solar panels in my arsenal (also from Near Future) provide only 72 electricity per second and weigh 1.2 tons. So you need about 140 such panels to power the big VASIMR, meaning 168 tons just of solar panels, more than the whole ship currently weighs, so the TWR would be even worse than it is already . Not to mention the lag of so many parts.

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Anyway, given the limitation of RCS fuel, I think I'm going to try redesigning this with scads of reaction wheels instead. It's not like I don't have the power to run as many as I need .

[Geschosskopf]

The Argonian was en route to Duna but I decided I need to revise the design to get rid of the dependence on RCS fuel. And I wanted Jeb to fly the new version so there was nothing for it but to HyperEdit back to Kerbin and have Jeb test the capsule recovery system, which worked. Then I terminated the main body of the Argonian and redesigned it. Here's the new Argonian Mk 2.

I removed all the RCS tanks and thrusters and replaced them with 9 more of the 2.5m SAS units (20 torque each). This proved totally sufficient to orient the ship, no doubt helped by having the mass closer to the middle to reduce the moment of inertia. I also replaced the 8 mid-size reactors with 8 small-size reactors, and stuck these on the SAS units as that was the only place for them, to move that weight to the center, too. The result was a savings of about 23 tons, which increased the TWR in very high Kerbin orbit to 0.08 and also upped the delta-V to over 40,000.

Then I did a test burn of the big VASIMR to make sure I had enough juice. Yup. It apparently uses more than the listed 10,000 EC/sec because 4 of the small auxiliary reactors didn't do it, it needed 8 as shown here. That makes for 10,405 EC/sec generated. When I 1st throttle up the engine, the available charge drops by about 200 but then holds steady, apparently because the reactors need to throttle up to match the usage. But anyway, in this configuration, I've got unlimited maneuvering and all 82kN of thrust the engine can put out, without worrying about it sucking the ship dry.

So, after HyperEditing the thing back into a 40Mm orbit and full tanks, it was off to Duna again. Because this all happened the same day as the initial burn on the real launch window, I had to go around Kerbin again to get the right angle, which at this distance was a 9-day trip. Thus, the window wasn't as good and the burn needed 1371m/s over 28.5 minutes. Thank goodness for MJ. In fact, this burn was so long that I had to leave it running while I picked up one of my nephews from school. When I came back, however, all was fine, running in 1x some hours before leaving Kerbin's SOI.

I did a couple of mid- and late-course tweaks to give myself a prograde Pe just above Duna's atmosphere and did a capture burn into a 40Mm orbit again. I do these huge orbits because they keep the burn times low on captures, and circularizing them and fixing inclination is very cheap. Then, when it's time to leave, the orbital radius is so huge that I can keep burning the desired direction the whole time instead of having the problem with long burns at low altitude. I think the efficiency balances out to some extent when you consider the whole arrival/departure process instead looking at just 1 or the other. But efficiency isn't a great concern when you have so much smash in the tank.

After only a short stay at Duna, a nice Dres window came up so I went there next. This took about an 15-minute burn followed by this 9-minute mid-course correction.

Dres has a very small SOI and I knew from the KTC's small VASIMR probe that it really pays to get the Pe as low as possible so you cut through as much SOI as possible. So I came in for 30km and set up a burn for the biggest elliptical orbit (and shortest burn time) I could get. This worked out to be 20Mm Ap, about 900m/s, and an 18-minute burntime starting WAY out from Dres. And all thise despite the TWR showing as not too shabby near Dres. In fact, as I passed Pe, I decided I'd better get off the node marker and burn pure retrograde if I wanted to stay here. Anyway, it all worked out OK and I got the 20Mm orbit, which I then plane-changed and circularized.

'

This pic, with the capture burn still going on, shows an interesting thing about argon tanks. Despite being stacked and fuel-lined in a regular asparagus arrangement, all the tanks drain at once like RCS. Thus, if you have any desire to do something like the Argonian yourself, you really need TAC Fuel Balancer. Here, I'm using that to force the tanks to drain in the desired asparagus sequence. The Argonian has 45 tanks in stacks of 5, so the last 10 tanks on the TAC list are those of the 1st pair of asparagus. You might also have noticed in other pics that the side tank stacks have lights of different colors on them. That's to help me locate the proper tanks to be draining at the time. Anyway, as you can see here, going from Kerbin to Duna to Dres has consumed 3/5 of the 1st set of side tanks.

Then it was time to go to Jool. If you look closely at about 8 o'clock to Kerbol and just above the rear edge of the side tanks, you can see Dres out there 20Mm away. The Jool transfer burn (less up-coming mid-course correction) was 740m/s over 14.5 minutes. At this point in the trip (before the transfer burn), the Argonian still had 83% of its fuel and it will still be a while before I drop the 1st set of side tanks.

And this is where I had to stop for the day. Jeb reports no problems with the ship. It's only me having the problem, having to sit thorugh all these very long burns. But that's why there's MJ, TV, books, and visiting nephews. But OTOH, the nephew is a KSPer, too, so wanted to see all this instead of doing something else, so there we sat watching most of the time. But OTOH, I did have to fiddle with TACFB a fair amount during the burns (it kept forgetting how I'd set it before and fuel started going every which way).

I'm starting to get bored with this already

[Geschosskopf]

Well, the Argonian has reached Jool. This pic shows it doing the final burn to settle into a circular, low-inclination orbit just outside Tylo's. Mucking about around Jool needed several burns, most of 5-10 minutes. First a capture burn from a 200km Pe into a huge ellipse with an Ap way out beyond Pol. Then a plane change out near Ap to get rid of most of the inclination I had coming from Dres, followed by raising the Pe out just past Tylo, taking off the rest of the inclination, and finally circularizing. The Argonian still has over 75% fuel remaining so the question becomes, what to do next?

It's day 788 of the mission. Half of that was spent traveling between Dres and Jool, and getting settled in at Jool. I had thought of gong to Eeloo next but the window is 10 YEARS away, so I won't be doing that. Instead, I'll go see Eve and Moho, although there's a strong temptation to do a sundive from Jool with the idea of going interstellar, just to be done with the whole thing . Anyway, to avoid impossibly long capture burns at the inner planets, I figure to step my way down there, Jool -> Duna, Duna -> Eve, Eve -> Moho. We'll see what happens.

This is THE most boring thing I've ever done in KSP. I started it just to take a break from too much work on the KTC, and have only continued it to mark time until another nephew (and also an avid KSP-er) arrived for Thanksgiving. He can help me with some of the donkey work of launching, docking, and transferring the vast KTC armada, which I figure we'll start doing today .