totm january 2020 Community Caveman Jool 5 mission

[Pds314]

1 hour ago, ManEatingApe said:

There's 78 m/s left in a still attached upper stage. This may be enough to circularize to an 80 km x 80 km orbit (be as precise as possible)

If not, then send up a DELTA and use it as a tug. We have to conserve the precious full fuel tanks in the bottom part for the mission proper.

How do I access the mission run itself?

On an aside, experiments show that DELTA can access essentially any orbit from any other orbit if you also use the monoprop and/or aerobrake. Though how much fuel you end up with after that, especially if you want to do something stupid like send it into a prograde 80x80 orbit and plane change->aerobrake->apkick into a retrograde 500x500 orbit, is another thing entirely. Also harsh maneuvers with monoprop are slowish.

Edited September 3, 2019 by Pds314

[ManEatingApe]

2 hours ago, Muetdhiver said:

=> Badge : Jool 5 Badge with a trilobite or caveman instead of the kerbal ?

I shall pass on your suggestions!
PR merged, MIKE is now in orbit.

1 hour ago, dvader said:

I've updated LIMA to the final version. Only minor changes this time. Added a docking port (on the radial decoupler on the belly), rotated the ladder to sideways and added a launcher rocket.

Excellent! I've merged your PR.

1 hour ago, dvader said:

Filming a Kerbal on a ladder (twice) just so I can compare screenshots of the drag vectors really makes me question my own hobbies I still don't really believe the results though. I still expect it to be due to some other effect or just random chance but it really seems to matter.

You are not alone

1 hour ago, Pds314 said:

How do I access the mission run itself?

Checkout the latest commit of the repo (tagged "v6" ) then load the "latest" savegame.
@Pds314 You have the mutex, I've updated the OP.

Thanks for all the contributions folks, we're making excellent progress.

Edited September 3, 2019 by ManEatingApe

[Pds314]

I have circularized at a 79950*79950 orbit on internal fuel with 37 m/s remaining and recorded video. However, I think I should put a DELTA or two somewhere nearby to help with assembly.

[IncongruousGoat]

@ManEatingApe I'll take a fuel run.

[Pds314]

Alright. Docked DELTA to MIKE for temporary storage. Imma upload the Latest.sfs and the mission video.

I did a PR but I may have done something weird so LMK if something is wrong with it.

Edited September 4, 2019 by Pds314

[Pds314]

I'm gonna upload the 15 minute raw video as unlisted. I will link it here if anyone wants to edit it into a whole-mission video/screenshot compilation.

Edited September 4, 2019 by Pds314

[Pds314]

 

[Jacke]

@ManEatingApe, I'll try a fuel run.

Slot me after @IncongruousGoat.  I'll watch his and that's should give me the rough performance on launching a FOXTROT.

I'll get a circular orbit just below MIKE and phased to be behind.  That should allow me to have a good approach to near rendezvous range and start the zero-relative-V then thrust towards it cycle to close to docking range.

Which means tomorrow I've got to get onto running this beastie.

[Pds314]

Oh, and a quick note on the drop tank I left in orbit, it should decay within one orbit and survive reentry, for a 100 m/s crash into the ground. The periapsis is at around 60 km. So it is not a permanent piece of orbital debris. Switching to it will cause it to fall out of the sky.

Edited September 4, 2019 by Pds314

[Muetdhiver]

I think that given that we have a nice 80x80 orbit, we could detach MIKE's top tank.

Just be aware that MIKE alone has no probe core (saves weight, and we'll have plenty of those on bord anyway).

Two questions :

1) I saw that TANGO has a bottom docking port (which is nice). Does it block the spark thrust or not ?

2) It would be nice to have LIMA and KILO masses to get the final dV budget. (And see if we need extra fuel tanks or not)

[IncongruousGoat]

1 minute ago, Muetdhiver said:

1) I saw that TANGO has a bottom docking port (which is nice). Does it block the spark thrust or not ?

Both docking ports are on separators. They're designed to be jettisoned before the lander is used as a lander.

[Muetdhiver]

Just now, IncongruousGoat said:

Both docking ports are on separators. They're designed to be jettisoned before the lander is used as a lander.

oO I missed that. Clever.

I will do an updated dV budget with guesses for LIMA & KILO at 2.5t and 1.2t respectively.

[Pds314]

I will fly a FOXTROT if we need.

11 minutes ago, Muetdhiver said:

oO I missed that. Clever.

I will do an updated dV budget with guesses for LIMA & KILO at 2.5t and 1.2t respectively.

KILO, including both the reentry pod and the fuel return stage from LLO with a ~500 m/s margin, is 3.0 tonnes. x_X. Maybe that's not how we are gonna use it though? The reentry pod itself is nowhere near that.

Edited September 4, 2019 by Pds314

[Muetdhiver]

17 minutes ago, Pds314 said:

I will fly a FOXTROT if we need.

KILO, including both the reentry pod and the fuel return stage from LLO with a ~500 m/s margin, is 3.0 tonnes. x_X. Maybe that's not how we are gonna use it though? The reentry pod itself is nowhere near that.

Don't worry, with a 3T KILO we still have ~2575 dV on MIKE with the 3x3 tanks.

If we assume 2275 for the transfer that leaves 300 for capture (about 200) and 100 m/s for safety. This also means that we have no fuel to lower Pe to Tylo.

I see two options :

A) Pack an additional 3x3 of fuel, for an extra 650 dV (enough for Jool plane correction and lowering Ap to Tylo)

B) Grav assist from Eve (there is a window for it, but getting the Beta angle right is going to be an "interesting" problem)

I will do some exploration on idea B, but it's not a easy thing.

[dvader]

1 hour ago, Muetdhiver said:

2) It would be nice to have LIMA and KILO masses to get the final dV budget. (And see if we need extra fuel tanks or not)

LIMA is 1.635t and KILO is 3.135 without orbiting engine = 4.77t total

We need at least 650 dV for orbital insertion (sandbox best case). Assuming we don't need more than 150dV for corrections we should be fine with 1.5 fuel tanks (FLT100 + FLT200) and a Terrier to get a total of 6.997t. That gives us 816m/s for orbital insertion. But, maybe 2xFLT200 and 7.56t/1040dV is a safer choice . We need fuel both to adjust the orbit so we hit Laythe and to raise/lower the PE once we reach Laythe. Thoughts?

The plan would be to use the orbital engine to de-orbit LIMA+KILO to 48km, release LIMA and then raise the PE for KILO again. It should not cost very much and could probably be done on fumes alone. We use whatever is left in LIMA + KILOs reserve fuel for rendezvous.

Long story short, 7-7.5t for LIMA+KILO. We could perhaps save 0.075t by putting KILOs docking port underneath the nose cone and ditch the cone once in space.

 

[Pds314]

50 minutes ago, Muetdhiver said:

Don't worry, with a 3T KILO we still have ~2575 dV on MIKE with the 3x3 tanks.

If we assume 2275 for the transfer that leaves 300 for capture (about 200) and 100 m/s for safety. This also means that we have no fuel to lower Pe to Tylo.

I see two options :

A) Pack an additional 3x3 of fuel, for an extra 650 dV (enough for Jool plane correction and lowering Ap to Tylo)

B) Grav assist from Eve (there is a window for it, but getting the Beta angle right is going to be an "interesting" problem)

I will do some exploration on idea B, but it's not a easy thing.

B sounds pretty convoluted considering that we are doing Caveman mission and transfers will not be within a few kilometers of target but a few tens of thousands of kilometers in many cases.

[Pds314]

48 minutes ago, dvader said:

LIMA is 1.635t and KILO is 3.135 without orbiting engine = 4.77t total

We need at least 650 dV for orbital insertion (sandbox best case). Assuming we don't need more than 150dV for corrections we should be fine with 1.5 fuel tanks (FLT100 + FLT200) and a Terrier to get a total of 6.997t. That gives us 816m/s for orbital insertion. But, maybe 2xFLT200 and 7.56t/1040dV is a safer choice . We need fuel both to adjust the orbit so we hit Laythe and to raise/lower the PE once we reach Laythe. Thoughts?

The plan would be to use the orbital engine to de-orbit LIMA+KILO to 48km, release LIMA and then raise the PE for KILO again. It should not cost very much and could probably be done on fumes alone. We use whatever is left in LIMA + KILOs reserve fuel for rendezvous.

Long story short, 7-7.5t for LIMA+KILO. We could perhaps save 0.075t by putting KILOs docking port underneath the nose cone and ditch the cone once in space.

 

3135? Are you leaving the Nose cone on or something? It's 3040 kg in the editor with one docking port and no nosecone. The drones should grab it by the nosecone, and attach it by the base, so they can take the nose cone off with them and get rid of it. Say, by spinning so hard it deorbits, or just dropping it as debris.

Of that 3040:
30 kg is docking port and stack separator.
590 kg is reentry module.
2420 kg is return transfer stage (of which 2000 kg is fuel).

So only 3040 kg is going to Jool, with 3010 kg when it starts its burn home with 3544 Delta-V. At burnout there will be 1010 kg, of which 590 kg will be returning through the atmosphere and 420 kg that is transfer stage, 290 kg will remain after the heat shield is dropped, and 235 left after the fairing is deployed. Which will all be destroyed on impact save for the Kerbal who is either inside and safe because the impact is slightly below 50 m/s or outside and parachuting and safe.

One thing I did not do, but we could before launch, is drain most of the ablator. It's good enough for a 30-degree Jool reentry so it should definitely survive Kerbin's atmsosphere at like 4 km/s or something with much less than 200 kg of ablator. So we could cut that back down to something sensible like 40 or 60 kg of ablator. At 60 kg, that means Lowering KILO mass to Jool to 2900 kg even, and lowering Kerbin reentry vehicle mass to 450 kg. With 3889 m/s of Delta-V.

Edited September 4, 2019 by Pds314

[Muetdhiver]

51 minutes ago, dvader said:

LIMA is 1.635t and KILO is 3.135 without orbiting engine = 4.77t total

We need at least 650 dV for orbital insertion (sandbox best case). Assuming we don't need more than 150dV for corrections we should be fine with 1.5 fuel tanks (FLT100 + FLT200) and a Terrier to get a total of 6.997t. That gives us 816m/s for orbital insertion. But, maybe 2xFLT200 and 7.56t/1040dV is a safer choice . We need fuel both to adjust the orbit so we hit Laythe and to raise/lower the PE once we reach Laythe. Thoughts?

The plan would be to use the orbital engine to de-orbit LIMA+KILO to 48km, release LIMA and then raise the PE for KILO again. It should not cost very much and could probably be done on fumes alone. We use whatever is left in LIMA + KILOs reserve fuel for rendezvous.

Long story short, 7-7.5t for LIMA+KILO. We could perhaps save 0.075t by putting KILOs docking port underneath the nose cone and ditch the cone once in space.

 

I think I need some clarifications :

If I get it correctly, we will need an FLT400 (FLT100+200 with less safety) worth of fuel to get LIMA & KILO to laythe.

So, here is an idea : can we do something like KILO+LIMA+LIMO (couldn't resist, that would be orbital engine + 1.5fuel tank)

Then : use what's left of MIKE to lower Pe from Tylo level, then detach and complete with LIMO fuel. Get the Laythe encounter, get into high elliptical orbit. leave KILO with it's return fuel there. Send LIMA+LIMO to low laythe orbit. Do the laythe mission, rendez-vous with LIMO. leave what's left of LIMA behind and rendez-vous with KILO. Go back to Kerbin. (Only worry here is that the more rendez vous, the more RCS fuel we'll use on the kerbal). What would be the DV cost of such a plan ?

As for mike, using 3.04T for KILO, 1.635T LIMA and 2.0T LIMO, I get a dV budget of 2.45 km/s for MIKE, which is too short. With three extra 3T tanks we get to 3.1 km/s which is enough.

@Pds314 I used to think that caveman grav assist where impossible. I even did tests that went very poorly. However, with the planning tools I have, it might be doable. I will do a prototype mission, as it will be a good futher proofing of the NavTool.

Edited September 4, 2019 by Muetdhiver

[dvader]

6 minutes ago, Pds314 said:

3135? Are you leaving the Nose cone on or something?
 

Yes, I was. It was in a very practical position for attaching LIMA at the top and an engine at the bottom

 

2 minutes ago, Muetdhiver said:

I think I need some clarifications :

If I get it correctly, we will need an FLT400 (FLT100+200 with less safety) worth of fuel to get LIMA & KILO to laythe.

So, here is an idea : can we do something like KILO+LIMA+LIMO (couldn't resist, that would be orbital engine + 1.5fuel tank)

Then : use what's left of MIKE to lower Ap from Tylo level, then detach and complete with LIMO fuel. Get the Laythe encounter, get into high elliptical orbit. leave KILO with it's return fuel there. Send LIMA+LIMO to low laythe orbit. Do the laythe mission, rendez-vous with LIMO. leave what's left of LIMA behind and rendez-vous with KILO. Go back to Kerbin. (Only worry here is that the more rendez vous, the more RCS fuel we'll use on the kerbal). What would be the DV cost of such a plan ?

I think the weight savings probably wont be much but it might still be worth it. Leaving KILO in high orbit would save us about 600dV so about 0.5t of fuel (?).  Adding a probe core, ladder, battery, fuel and stuff to LIMA would eat up most of the savings.

We could also save 0.4t by switching the Terrier on LIMO for a Spark but since we need to burn off about 600dV, it would take quite a while with a Spark and a TWR around 0.3. It might still be worth it though.

[Pds314]

23 minutes ago, Muetdhiver said:

I think I need some clarifications :

If I get it correctly, we will need an FLT400 (FLT100+200 with less safety) worth of fuel to get LIMA & KILO to laythe.

So, here is an idea : can we do something like KILO+LIMA+LIMO (couldn't resist, that would be orbital engine + 1.5fuel tank)

Then : use what's left of MIKE to lower Ap from Tylo level, then detach and complete with LIMO fuel. Get the Laythe encounter, get into high elliptical orbit. leave KILO with it's return fuel there. Send LIMA+LIMO to low laythe orbit. Do the laythe mission, rendez-vous with LIMO. leave what's left of LIMA behind and rendez-vous with KILO. Go back to Kerbin. (Only worry here is that the more rendez vous, the more RCS fuel we'll use on the kerbal). What would be the DV cost of such a plan ?

As for mike, using 3.04T for KILO, 1.635T LIMA and 2.0T LIMO, I get a dV budget of 2.45 km/s for MIKE, which is too short. With three extra 3T tanks we get to 3.1 km/s which is enough.

@Pds314 I used to think that caveman grav assist where impossible. I even did tests that went very poorly. However, with the planning tools I have, it might be doable. I will do a prototype mission, as it will be a good futher proofing of the NavTool.

We could possibly cut KILO to as light as like 2860 or so kg without changing fuel load. And 2268 without lowering Delta-V but by replacing the tank with two smaller ones.

Imma test and then upload an optional "KILO LIGHT" optimized to have >3500 m/s of Delta-V but be lighter. Looking back at former tests I think even 20 kg of ablator might actually be enough for Jool reentry, let alone Kerbin.

Edited September 4, 2019 by Pds314

[Muetdhiver]

9 minutes ago, dvader said:

Yes, I was. It was in a very practical position for attaching LIMA at the top and an engine at the bottom

 

I think the weight savings probably wont be much but it might still be worth it. Leaving KILO in high orbit would save us about 600dV so about 0.5t of fuel (?).  Adding a probe core, ladder, battery, fuel and stuff to LIMA would eat up most of the savings.

We could also save 0.4t by switching the Terrier on LIMO for a Spark but since we need to burn off about 600dV, it would take quite a while with a Spark and a TWR around 0.3. It might still be worth it though.

I think using a spark makes a lot of sense. It will be enough even for the return. It's much better than multiple RDVz.

Speaking of which, how much dV do we really need on KILO ?

[dvader]

Another option is adding a bare fuel tank between KILO and LIMA and using KILOs engine for propulsion assuming fuel crossfeed across the heat shield is allowed in the settings (I've done that mistake many many times before). It would save us the weight of another engine.

@Pds314 Have you tried skipping the heat shield and just using the base of the fairing? I think it has a very high heat rating but you would probably need another reaction wheel to keep it upright.

@Muetdhiver If you get grav assists to work, it would be another Caveman worlds first

So many possibilities and so little time...

 

[Muetdhiver]

1 minute ago, dvader said:

Another option is adding a bare fuel tank between KILO and LIMA and using KILOs engine for propulsion assuming fuel crossfeed across the heat shield is allowed in the settings (I've done that mistake many many times before). It would save us the weight of another engine.

@Pds314 Have you tried skipping the heat shield and just using the base of the fairing? I think it has a very high heat rating but you would probably need another reaction wheel to keep it upright.

@Muetdhiver If you get grav assists to work, it would be another Caveman worlds first

So many possibilities and so little time...

 

TBH if we could simply use KILO engine, it would be a lot better. (less dry mass).

An option to consider w.r.t. to the fuel cross feed is using a 1.25 payload bay (2.9K heat tollerance) as a heatshield/aerobrake combo. That's what I used to get back from jool. You have to do multiple aerobrakings though, but since the craft will be super light, it should be rather easy to get it to the ground.

[Pds314]

So far KILO tests without a heat shield indicate that it depends on the reentry whether it will survive. But that both should survive a Hohmann transfer from Jool.

3.6 km/s reentry, 14 km PE
No Heatshield: survived.
20 Ablator Heatshield: survived.

4.9 km/s reentry, 26 km PE
No Heatshield: Survived. Just barely.
20 Ablator Heatshield: survived.

5.1 km/s reentry, 50 degree angle to the ground.
No Heatshield: Failed. fairing overheated.
20 Ablator Heatshield: survived.

6.6 km/s, 60 degree angle to the ground.
No Heatshield: Failed. fairing overheated.
20 Ablator Heatshield: Failed. fairing overheated.

Edited September 4, 2019 by Pds314

[Pds314]

Will add a KILO ULTRALIGHT craft. Mass: 1810 kg. It needs a reasonable perikee though. You can't just throw it into a hypervelocity vertical descent and hope for the best.