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Duna Outpost Mission Architecture Challenge


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16 hours ago, Kerbolitto said:

Oh yeah that's a very good idea, I forgot you could do that, since I'm using lots of Nukes.. ! You might need to put batteries in a cargobay but it's not that harsh to capture !

I meant that you could launch every SLV until Y10 with 0 fuel, by refuelling them using Minmus to top up your TV at any planned transfer, in the end that's a lot of weight saving in my opinion.

As for the DST, I'm sending it empty with some other stuff on 3rd window to refuell it around Duna, but the transfer stage with the rest of the payload will be refuelled at Minmus.

So the 1st ISRU at Minmus will still be needed to fill the nuke pods at every transfer.

Good point, I'll run some numbers and see which of those would be lighter. My DST is actually the same vehicle as one of my TVs, so at least one of them has to at least once do a Duna-Kerbin-Duna flight without refueling.

3 hours ago, Death Engineering said:

[...]

Yes.

Thanks, how about enriched uranium?

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@Mad Rocket Scientist

Well if you look at hohmann transfer, you put average 123t. in orbit at each window.

Roughly, if you go nuclear, that's 25t. of Liquid fuel each transfer to push 123t. at Duna (1780dV with high margin), not accounting monoprop and Lf+Ox (to power your relays for example, or a deorbiter).

So at Year 8 that's 100t. of Lf which means 20% of all your SLVs has to be liquid fuel.

If you are able to design a light ISRU you may have a return on investment as soon as the 2nd launch.

 

Edited by Kerbolitto
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8 hours ago, Kerbolitto said:

Quick note, excuse me if I sound somehow pedantic but english is not my first language and after re-reading, I'm think I'm writing in a very litteral way :D.

 

2 hours ago, hoioh said:

For a Frenchman your English lauguage skill is excellent! The average Dutchman (I'm Dutch, but certainly don't think of myself as average) would be jealous of you!

My French is certainly worse ;)

You both speak more languages than me. I know enough Spanish to get in trouble, and sometimes back out again. I know a few swear words in Tagalog and a smattering of Japanese. But mostly I speak English. Oh and computer code, if that counts.

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 @Kerbolitto , @Mad Rocket Scientist: I plan to snatch an asteroid first; having fuel on tap in LKO means that you need no extra tanks (or a schedule) to ship fuel back and forth.

Currently struggling with life support. People die when I'm not focused on the vessel.

Edit: It seems as if TACLS doesn't recognize the PP reactor as a power source, at least not if it's the sole power supply. That might become interesting.

 

Edited by Laie
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@Laie

You got time to get a large asteroid down in LKO before first transfer window ? In the 180x180 maximum SLV's orbit ? :0

Might be feasible if you're lucky, with aerobraking, maybe Mun slingshot to change the plane but it might be short before D210 ? I think its a fantastic idea you could get rid of the ISRU propulsion.

How much fuel can you extract from a big asteroid ? I've never put a fuel-base on one, down in LKO.

Edited by Kerbolitto
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34 minutes ago, Kerbolitto said:

You got time to get a large asteroid down in LKO before first transfer window ?

Oh, guess so? I've got no plans for the fist window myself, so I'm not in a hurry. But you can definitely have your first asteroid at Kerbin by day 100 or thereabouts. Wrestling it into LKO by day 160 should be entirely doable and *picks up slide rule* cost you about a quarter of it's mass when using nukes. Class E (the biggest) can be anything from 800-3000t, I hear; personally I've never seen one under 1500t or with less than 80% ore content. I figure that one of these should last me for the entire duration of the challenge.

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On 8/11/2018 at 10:40 AM, Death Engineering said:

What's it used for?

Near future engines and power make nuclear engines run on enriched uranium. For most of the engines, it's only being converted to depleted uranium, but one of them loses a small amount while the engine is running, so it's technically a propellant.

On 8/11/2018 at 10:44 AM, Kerbolitto said:

@Mad Rocket Scientist

Well if you look at hohmann transfer, you put average 123t. in orbit at each window.

Roughly, if you go nuclear, that's 25t. of Liquid fuel each transfer to push 123t. at Duna (1780dV with high margin), not accounting monoprop and Lf+Ox (to power your relays for example, or a deorbiter).

So at Year 8 that's 100t. of Lf which means 20% of all your SLVs has to be liquid fuel.

If you are able to design a light ISRU you may have a return on investment as soon as the 2nd launch.

That's convincing, I haven't had enough time to do the math yet. The real question how much extra tanks are required to allow a duna -> kerbin transfer with no payload, then a kerbin -> duna transfer with payload, all without refueling.

5 hours ago, Laie said:

 @Kerbolitto , @Mad Rocket Scientist: I plan to snatch an asteroid first; having fuel on tap in LKO means that you need no extra tanks (or a schedule) to ship fuel back and forth.

Currently struggling with life support. People die when I'm not focused on the vessel.

Edit: It seems as if TACLS doesn't recognize the PP reactor as a power source, at least not if it's the sole power supply. That might become interesting.

I was considering that, but got concerned about how much fuel I'd get, and how long it would take to grab the asteroid. Of course I'd probably only need it by the second window...

Now I have to calculate how many tons of propellant I'll need for the entire mission. :) 

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3 hours ago, Mad Rocket Scientist said:

That's convincing, I haven't had enough time to do the math yet. The real question how much extra tanks are required to allow a duna -> kerbin transfer with no payload, then a kerbin -> duna transfer with payload, all without refueling.

Why won't you refuel in Duna SOI ? Say that you inject average 123t., you need 6 nukes to get 0.3TWR (too high but allows for heavier payloads), so that's 25t. fuel contained in 2.5t. tankers + 18t. engines + docks / probe / battery / stuff. So your transfer stage is +/- around 22/23t. empty. You will only need 6t. of Lf to get 1800m/s (700m/s duna -> kerbin without using Ike, 1100m/s circu LKO). So based on this average, fuel capacity of the transfer stage alone is 3 mk1 liquid fuel fuselage.

Again this is very quick math and average assumption but it's a baseline. For example my 2nd transfer to Duna weighted 183t. with tanks half empty so I needed 8 nukes. With 2300m/s total I was able to retroburn 4 nukes to LKO once injection was complete. This retroburn burned 780 Lf (should have been 600Lf for 4 nukes, 1200m/s quite far from Pe + maybe 500-600 circu) but there was more weight to slow down due to a little habitat + mk3 fuselage tank's weight, so it's +/- around the numbers stated above.

 

edit : its funny to see patterns once everything succeeded and it may seems that I had everything under control, but most of my flights were done the empirical way, after many, many fuel tests in the SPH to see how I should combine the various modules / engines / tanks in orbit. :rolleyes:

Edited by Kerbolitto
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Did some redesigning today:

New base:

BW4EYno.jpg

 

New orbital base:

UJwrw10.jpg

 

And a new mining rig that works and can carry a lvl5 engineer along to refuel a massive tank in just 1.5 to 2 hours:

kxtm5XH.jpg

The engineer is crucial! Without him this rig would refuel the same tank in just under a year... Just brought him a porthole and some food/O2/H2O and he'll be fine for a while!

Next up: redesigning my SLV for 79.0415t (the exact limit for a 9 launch schedule, last launch departing at Y9D465 or whatever the last day prior to Y10 is and ALL possible mass accounted for within this window)

Oh and my spreadsheet is growing out of control now, once I've finished the planning stages I might clean it up and make it suitable for general use if by then anyone is still interested in it

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1 hour ago, Kerbolitto said:

Why won't you refuel in Duna SOI ? Say that you inject average 123t., you need 6 nukes to get 0.3TWR (too high but allows for heavier payloads), so that's 25t. fuel contained in 2.5t. tankers + 18t. engines + docks / probe / battery / stuff. So your transfer stage is +/- around 22/23t. empty. You will only need 6t. of Lf to get 1800m/s (700m/s duna -> kerbin without using Ike, 1100m/s circu LKO). So based on this average, fuel capacity of the transfer stage alone is 3 mk1 liquid fuel fuselage.

My post wasn't clear, I am going to refuel in Duna SOI. :)

1 hour ago, Kerbolitto said:

Again this is very quick math and average assumption but it's a baseline. For example my 2nd transfer to Duna weighted 183t. with tanks half empty so I needed 8 nukes. With 2300m/s total I was able to retroburn 4 nukes to LKO once injection was complete. This retroburn burned 780 Lf (should have been 600Lf for 4 nukes, 1200m/s quite far from Pe + maybe 500-600 circu) but there was more weight to slow down due to a little habitat + mk3 fuselage tank's weight, so it's +/- around the numbers stated above.

 

edit : its funny to see patterns once everything succeeded and it may seems that I had everything under control, but most of my flights were done the empirical way, after many, many fuel tests in the SPH to see how I should combine the various modules / engines / tanks in orbit. :rolleyes:

It is interesting. 

@hoioh, what mod are you using for those ducted electric fans? Also, that miner looks good.

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@Mad Rocket Scientist

The ducted electric fans are part of the feline utility rovers mod:

Which through some mismatching of outdated mods mostly doesn't work for me, but these do! Actualy everything works, but there's some parts with reflections on them which get handled incorrectly and the windows and solar panels show up pink, as do most stock ones and stock cabins and cockpits as well (the latter two actually showing up completely pink, not just the reflective surfaces) I've no idea what's causing it

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One of the usual woes: KSP vessels are just too damn tall. Also, trying to utilize the allowwed payload to the fullest forces compromises which I'm not too happy about. Here you have  the relay satellites  stuck in between the two halves of the asteroid snatcher. I've spent quite some time making somewhat attractive and reasonably credible-looking vessels, and now this, on the very first launch.

minerLV.jpg

...but there's no way I'm going to leave 5t payload capacity unused. Some things are just. not. done.

5 minutes ago, Kerbolitto said:

send tiny bits of life support or monoprop

ETA: Nothing in orbit to send it to, yet.

And for good measure, a shot of the black LV at night:

minerLV2.jpg

At it's core it's your standard rocket SSTO. Only that it does Atlas-style staging (those boosters will drop soon), so, not an SSTO. It's scaled up to give a 5m payload diameter at credible length, while maintaining the mass and performance of a 3m booster. Seriously, some payloads will be bulky and I hate bubble-head fairings.

Edited by Laie
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I've gotten sidetracked working on a Jool-5 SSTO carrier. It's not as elegant as this entry from @McBalsam that I'm totally not making a poor copy of, but I'm happy with it so far. Anyway, I figure it's at least good practice for jamming a bunch of payload into a reasonable-ish sized launch vehicle.

 

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Mmh I may have troubles with KerbinEarlyReturn :D

I planned a solar intersection which costs 6600m/s in total, 5500m/s (approx 30minutes burn) to catch up with the target.. Ship's coming so fast that it would enter and leave Kerbin SOI in less than 2 days. There's a backup plan but it's far less fun (also re-entry is more standard) so I'm not sure what I'll choose..

Should I go full kerbal on this ?

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9 hours ago, Kerbolitto said:

Should I go full kerbal on this ?

Always!

If you have the DV that is. Maybe an eve slingshot would conserve DV with similar results?

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1 hour ago, hoioh said:

Always!

If you have the DV that is. Maybe an eve slingshot would conserve DV with similar results?

I tried an Eve slingshot when coming down from Duna and it would have been very effective, except the trip would take too much time to complete the achievement. Aslo I can't intersect too far from Kerbin because at the angle it's coming, the departure burn and encounter would cost a lot more. So there's 2 options, one is to encounter the ship 1/2 days before Kerbin's Pe (6600m/s). Second is to wait the first retroburn of the ship (save 3300m/s) which will put it on a very elliptical orbit and an encounter with Minmus but time margins are tighter (10 days at best). :D

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minerLV3.jpg

The LV on it's way back. Stubby winglets give a small degree of crossrange capability -- the idea is that if i manage to land "at" KSC, I should be able to aim for the launchpad. Which is something I definitely want to try at some time. However, this launch went to a 60° orbit, draining most maneuvering fuel while making timing more demanding; being eager to get the mission under way, I had no patience for the LV. It landed safely, somewhere.

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