Roads to Duna: No Moar Boosters (UPDATES!)

[Nefrums]

I have actually ben trying to do a mission like this, but trying to make it as realistic as possible.  RSS, Life support, fuel boil-of, using the same launcher for everything etc.

It is turning out to be really really hard to design a realistic mars mission. 

[sevenperforce]

1 hour ago, mk1980 said:

a bit late for a rule suggestion, but did you consider a rule/achievement that gives a %bonus if all launches use the same launch vehicle (same rocket up to the fairing that holds the payload. or same space shuttle / SSTO except for the stuff inside the cargo bay/cargo fairing).

in the real world, design of the launch vehicle is a big deal and it would seem likely that a space agency would try to use the same vehicle for launches of payloads with similar sizes.

judging from the teaser image posted by Laie, it looks like he's doing that already and i think that's a pretty cool little detail that should be rewarded.

i probably won't be able to use the same vehicle for all launches, though. strapping a plane on top of a rocket is usually a recipe for disaster...

I did that as well. I'll go ahead and add it.

I hadn't thought of it initially, because there is no mass restriction on the launch vehicle so you can really do whatever you want. My launch vehicle for my Brute Force entry can probably put about 25 tonnes into LKO with a perfect gravity turn, etc., but my payload modules are all under 12 tonnes. But consistency is definitely worth some extra points!

1 hour ago, Nefrums said:

I have actually ben trying to do a mission like this, but trying to make it as realistic as possible.  RSS, Life support, fuel boil-of, using the same launcher for everything etc.

It is turning out to be really really hard to design a realistic mars mission. 

What a surprise!

Well, maybe the relaxed requirements of this mission will be more achievable. I'd love to see your mission architecture!

Edited September 8, 2017 by sevenperforce

[Kergarin]

1 hour ago, sevenperforce said:

I remember to enable crossfeed on stack decouplers but I always forget that you can enable crossfeed on radial decouplers.

The terminal stage of your launch vehicle can complete the rendezvous using its main engine(s), then provide attitude and roll control during docking, but it cannot provide RCS translation. The Falcon 9 upper stage can provide roll and attitude to its payload prior to decoupling, for example.

Ok. So no RCS on the terminal stage.

But what if the terminal stage docks the payload using its main engine only?

[sevenperforce]

4 minutes ago, Kergarin said:

Ok. So no RCS on the terminal stage.

But what if the terminal stage docks the payload using its main engine only?

Go for it!

[AeroGav]

On 06/09/2017 at 6:20 PM, sevenperforce said:

If you want to use nukes, you can do so, but only before leaving Kerbin's SOI. NERVAs can't be reliably restarted after a long period of time.

What's the justification for that btw?   NERVs weigh 3 tons, if you can only use them for the outbound transfer burn there is no point using one at all.

I am not aware of a reason why a NERV should be any more difficult to restart than any other turbopump engine.   Though for the lunar module engine they  stuck to pressure-fed hypergolic engine because that engine had to work.

What I am aware of, is that the 800+ ISP ratings for NERV assume the use of liquid hydrogen, which is subject to boiloff - hence can only be used on the mars injection burn.

NERVs can also run off liquid ammonia, storable, non-sooting propellant,  but only get 600 or so ISP in this case.     I assume the existing stock chemical engines are running off "storable" propellants too since none get over 350 ISP whereas real chemical engines can already hit 450+ with liquid hydrogen.

So how about I do a mission with a NERV but declare it to be a "Liquid Ammonia" engine and so don't use the last 25% of the fuel in my tank, because the ISP of 800 in game is too high for that.       However,  I will use the engine for the return journey since it's running on a "storable" fuel source..

[Laie]

As you can see, I took orbital assembly quite seriously. The first part would not quite fit into a Mk2 bay due to the sticks on the sides, but a Mk3 bay or 2.5m fairing would do nicely. The payloads and their masses:

1: 2322 kg core piece
2: 2310 kg long tank minus 250kg fuel
3: 2310 kg --"--
4: 2330 kg two short tanks plus 500kg fuel
5: 2260 kg crew module

Info for mission planners:
Departure from Kerbin was on Y1 D229 -- 1040m/s -- travel time 240 days
Miniscule midcourse corrections allowed to enter a nearly equatorial orbit around Duna, it would have taken ~730m/s to do so (including inclination change).

On the return trip, I didn't pay attention if a zero inclination could be reached. I spent 650m/s leaving Duna and would have needed 1040m/s to circularize at the inclination I had.

Mission Report in the spoiler.

Spoiler

Full disclosure: I didn't actually play through all launches because boring. I did, however, do all the docking. MJ alignment assistance made this easy, but please note that this isn't strictly necessary: the sole engine is on the core piece and hence certain to point in the right direction, which is the single most important issue.

For everything else, "looks about right" will do. It should suffice if you use stock SAS and point everything towards normal. The ladder still works when slightly off, worst thing that can happen is that the vessel starts rolling in the atmosphere (but then, that's what the reaction wheels are there for).

(not shown) Departure burn was short and uneventful, tanks still held a tiny amount on arrival but had to be jettisoned before entry. BTW, note that the probe core comes off before departure -- it only provides control during assembly.

The airbrakes give a lot of freedom when it comes to picking your eventual landing site. Or still making capture when you came in too high, which I didn't. A side benefit I didn't expect: the ladders make a *lot* of drag, I had to extend the opposite airbrake quite a bit to offset this.

Other than that, landing went without a hitch. That single parachute already slowed me to ~30m/s, the rest was simple.

On launch, I noticed that I messed up the staging, detaching the plain tanks first and carrying the ladders to orbit. That could be fixed in the field, but explains why the dV calculator suddenly shows different values. Ascent should have been steeper -- this vessel has quite noticable drag even on Duna. Still, there was enough dV to throw around, so what. And when the last drop tank was gone, this improved drag quite a bit.

Return home, again, was nothing special. Make maneuver, point, 40 second burn (650m/s). Corrections for about 10m/s to get me to a 30km PE and a safe landing. The docking port on the bottom quickly goes poof to expose the heatshield, but that's how it's supposed to be. It's just a scary moment because it happens to be the root part... other than that, business as usual --  I think most people have already landed a vessel just like this. All three splashed down safely on on Year 3, Day 84, 03:26.

 

[Laie]

3 hours ago, sevenperforce said:

The terminal stage of your launch vehicle can complete the rendezvous using its main engine(s), then provide attitude and roll control during docking, but it cannot provide RCS translation. The Falcon 9 upper stage can provide roll and attitude to its payload prior to decoupling, for example.

Sorry, but I'm afraid you're a bit too focused on Elon Style. What if the terminal stage is the Space Shuttle? Or KURS, or whatever they use to add things to the ISS? I don't think it's reasonable to expect a half-finished vessel to play the active role.

9 minutes ago, AeroGav said:

What's the justification for that btw?   NERVs weigh 3 tons, if you can only use them for the outbound transfer burn there is no point using one at all.

If I understand it correctly, it's to emulate the real-life problem of keeping it's fuel around for months.

Ceterum censeo, for the sake of reviewers and audience I'd strongly suggest to make it a rule that the payload should be clearly recognizable in the pictures. The ability to just tap fuel from the LV is an invitation to be not entirely honest. Simple before/after comparisons of mass are misleading if resources are consumed in the mean time (e.g. for docking).

[Kergarin]

53 minutes ago, Laie said:

As you can see, I took orbital assembly quite seriously. The first part would not quite fit into a Mk2 bay due to the sticks on the sides, but a Mk3 bay or 2.5m fairing would do nicely. The payloads and their masses:

1: 2322 kg core piece
2: 2310 kg long tank minus 250kg fuel
3: 2310 kg --"--
4: 2330 kg two short tanks plus 500kg fuel
5: 2260 kg crew module

Info for mission planners:
Departure from Kerbin was on Y1 D229 -- 1040m/s -- travel time 240 days
Miniscule midcourse corrections allowed to enter a nearly equatorial orbit around Duna, it would have taken ~730m/s to do so (including inclination change).

On the return trip, I didn't pay attention if a zero inclination could be reached. I spent 650m/s leaving Duna and would have needed 1040m/s to circularize at the inclination I had.

Mission Report in the spoiler.

  Reveal hidden contents

Full disclosure: I didn't actually play through all launches because boring. I did, however, do all the docking. MJ alignment assistance made this easy, but please note that this isn't strictly necessary: the sole engine is on the core piece and hence certain to point in the right direction, which is the single most important issue.

For everything else, "looks about right" will do. It should suffice if you use stock SAS and point everything towards normal. The ladder still works when slightly off, worst thing that can happen is that the vessel starts rolling in the atmosphere (but then, that's what the reaction wheels are there for).

(not shown) Departure burn was short and uneventful, tanks still held a tiny amount on arrival but had to be jettisoned before entry. BTW, note that the probe core comes off before departure -- it only provides control during assembly.

The airbrakes give a lot of freedom when it comes to picking your eventual landing site. Or still making capture when you came in too high, which I didn't. A side benefit I didn't expect: the ladders make a *lot* of drag, I had to extend the opposite airbrake quite a bit to offset this.

Other than that, landing went without a hitch. That single parachute already slowed me to ~30m/s, the rest was simple.

On launch, I noticed that I messed up the staging, detaching the plain tanks first and carrying the ladders to orbit. That could be fixed in the field, but explains why the dV calculator suddenly shows different values. Ascent should have been steeper -- this vessel has quite noticable drag even on Duna. Still, there was enough dV to throw around, so what. And when the last drop tank was gone, this improved drag quite a bit.

Return home, again, was nothing special. Make maneuver, point, 40 second burn (650m/s). Corrections for about 10m/s to get me to a 30km PE and a safe landing. The docking port on the bottom quickly goes poof to expose the heatshield, but that's how it's supposed to be. It's just a scary moment because it happens to be the root part... other than that, business as usual --  I think most people have already landed a vessel just like this. All three splashed down safely on on Year 3, Day 84, 03:26.

 

Great work! Mine looks so similar that I should stop working on it 

[Laie]

5 minutes ago, Kergarin said:

Great work! Mine looks so similar that I should stop working on it

Well, if you want to build the smallest possible three-person vessel you don't have many options.

That said, I've done the small fry mainly to get the obvious thing sorted out, so we can now proceed with the shiny missions. ISRU! Rovers! Reusable! My initial ideas were larger but also a lot more interesting than this tiny there-and-back thingy -- I'll certainly do another one just for the heck of it.

[sevenperforce]

12 minutes ago, Laie said:

Sorry, but I'm afraid you're a bit too focused on Elon Style. What if the terminal stage is the Space Shuttle? Or KURS, or whatever they use to add things to the ISS? I don't think it's reasonable to expect a half-finished vessel to play the active role.

Actually, Elon Style would be sending everything up ITS-wise, where the upper stage was already the payload. I was thinking of typical currently-in-use launch vehicles; Falcon 9 being only one of the upper stages which can provide roll and pointing but no RCS translation. For example, you wouldn't expect a Centaur upper stage, a DCSS, or a Soyuz Blok I third stage to actually perform docking with the ISS.

But I'll relax this.

14 minutes ago, Laie said:

Ceterum censeo, for the sake of reviewers and audience I'd strongly suggest to make it a rule that the payload should be clearly recognizable in the pictures. The ability to just tap fuel from the LV is an invitation to be not entirely honest. Simple before/after comparisons of mass are misleading if resources are consumed in the mean time (e.g. for docking).

Well, if I was worried about people cheating I could demand full mission video, but all these challenges are honor-system. I think people will get more out of going for various bonuses than they will from pinching fuel constraints.

15 minutes ago, Laie said:

43 minutes ago, AeroGav said:

What's the justification for that btw?   NERVs weigh 3 tons, if you can only use them for the outbound transfer burn there is no point using one at all.

I am not aware of a reason why a NERV should be any more difficult to restart than any other turbopump engine.   Though for the lunar module engine they  stuck to pressure-fed hypergolic engine because that engine had to work.

What I am aware of, is that the 800+ ISP ratings for NERV assume the use of liquid hydrogen, which is subject to boiloff - hence can only be used on the mars injection burn.

NERVs can also run off liquid ammonia, storable, non-sooting propellant,  but only get 600 or so ISP in this case.     I assume the existing stock chemical engines are running off "storable" propellants too since none get over 350 ISP whereas real chemical engines can already hit 450+ with liquid hydrogen.

So how about I do a mission with a NERV but declare it to be a "Liquid Ammonia" engine and so don't use the last 25% of the fuel in my tank, because the ISP of 800 in game is too high for that.       However,  I will use the engine for the return journey since it's running on a "storable" fuel source..

If I understand it correctly, it's to emulate the real-life problem of keeping it's fuel around for months.

I wanted my restrictions to mirror some of the constraints that real-life mission planners have to work around. There have been several proposals for Mars missions involving nukes, but they tend to be pretty seriously constrained. Can't fire nukes in atmosphere, often cannot restart, often need top-off or complex anti-boiloff systems. You also have to deal with radiation shielding, which is another reason to only use nukes on the outgoing trip. For all these reasons, it's simplest if I just say "No nukes after leaving Kerbin's SOI".

3 minutes ago, Laie said:

Well, if you want to build the smallest possible three-person vessel you don't have many options.

That said, I've done the small fry mainly to get the obvious thing sorted out, so we can now proceed with the shiny missions. ISRU! Rovers! Reusable! My initial ideas were larger but also a lot more interesting than this tiny there-and-back thingy -- I'll certainly do another one just for the heck of it.

Indeed! I think I am going to increase the bonus for Stayin' Alive, to make it more competitive. I hadn't realized how easy it would be to do a direct ascent.

[sevenperforce]

@Laie I'm going to set up the leaderboard. I've already got you down for Slow Climb. Are you eligible for Safety First, Old School, or Consistency, Good Sir? I assume you aren't eligible for Brute Force because it seems like you did propellant transfer.

[mk1980]

argh. will have to downscale my mission a bit. no way to beat Laie's score with a 10 ton vehicle. but i might be able to downsize some stuff. with all the  % bonuses i'm trying to get, i might at least get close...

 

one question @sevenperforce : can a mission get both "Loop the Loop" and "Elon Style" ? with those two combines and a few more "low hanging fruit", the modifier could be pushed up to maybe 70% or so, which would drop a mission with a 5 ton heaviest module down to a score of 1.5

Edited September 8, 2017 by mk1980

[sevenperforce]

17 minutes ago, mk1980 said:

argh. will have to downscale my mission a bit. no way to beat Laie's score with a 10 ton vehicle. but i might be able to downsize some stuff. with all the  % bonuses i'm trying to get, i might at least get close...

 

one question @sevenperforce : can a mission get both "Loop the Loop" and "Elon Style" ? with those two combines and a few more "low hanging fruit", the modifier could be pushed up to maybe 70% or so, which would drop a mission with a 5 ton heaviest module down to a score of 1.5

Yep! I have a mission architecture with precisely that design in mind. You can also pick up Stayin' Alive for a low additional mass cost if you have Loop the Loop. I designed the modifiers to allow pretty high reductions but never 100%, obviously. I wanted payload-per-launch to be the main metric, but I wanted design considerations to mix up the scoring as well to allow for more flexibility.

Edited September 8, 2017 by sevenperforce

[mk1980]

ok good. i have a few ideas to trim some fat off that glider. if i get that thing down to ~5 tons, i could probably also downsize the fuel tanks to a similar size since the ship will also need less fuel for the roundtrip.

[Laie]

1 hour ago, sevenperforce said:

@Laie I'm going to set up the leaderboard. I've already got you down for Slow Climb. Are you eligible for Safety First, Old School, or Consistency, Good Sir? I assume you aren't eligible for Brute Force because it seems like you did propellant transfer.

Sorry for not mentioning these points right away and leaving you to figure it out; also, sorry for not providing a single picture of the LV -- while I didn't actually play through all launches, I did two just to prove that it works. The rest was hyperedit.

I could easily have used one LV (but didn't). LES was present but nothing to write home about (really just a half-asssed attempt to score cheap points). And most important, I didn't notice that Brute Force forbids fuel transfers in orbit.

(thinks a little)

I'll have to slice things up in another way (yay! for the lifesaver) and will report back within a day or two. Then I will also be consistent and not only claim that I could have been.

Quick question: you may have noticed that the probe core and RCS tank didn't go to Duna (see upper left). Is it still the case that these would not count as "payload" for the purpose of this challenge?

Edited September 8, 2017 by Laie

[sevenperforce]

36 minutes ago, Laie said:

Sorry for not mentioning these points right away and leaving you to figure it out; also, sorry for not providing a single picture of the LV -- while I didn't actually play through all launches, I did two just to prove that it works. The rest was hyperedit.

I could easily have used one LV (but didn't). LES was present but nothing to write home about (really just a half-asssed attempt to score cheap points). And most important, I didn't notice that Brute Force forbids fuel transfers in orbit.

(thinks a little)

I'll have to slice things up in another way (yay! for the lifesaver) and will report back within a day or two. Then I will also be consistent and not only claim that I could have been.

I didn't REALLY want people to Hyperedit their modules into LKO, but given that you can literally overengineer your LV as much as you want (my LV, which I used for all four launches, has about twice the payload capacity of what I used), it doesn't really matter. Plus, you can get bonuses if you do fly it manually.

Quote

Quick question: you may have noticed that the probe core and RCS tank didn't go to Duna (see upper left). Is it still the case that these would not count as "payload" for the purpose of this challenge?

Eh, you can just count the probe core with RCS tank as the terminal stage of your LV. I guess I could make it another bonus if you don't use your LV for docking assistance? But then you run into the "what about fuel transfer" question and it just all gets hairy.

Edited September 8, 2017 by sevenperforce

[cratercracker]

 @sevenperforce

-------------------------

u want some patch?

 

[sevenperforce]

7 minutes ago, cratercracker said:

 @sevenperforce

-------------------------

u want some patch?

 

Sure, see what you can put together!

[Kergarin]

Another question 

Whats the payload when I send up a rocket which only transfers fuel to my empty Duna ship? Is it just the fuels weight or more?

[sevenperforce]

1 hour ago, Kergarin said:

Another question 

Whats the payload when I send up a rocket which only transfers fuel to my empty Duna ship? Is it just the fuels weight or more?

Just the fuel you transfer.

[tseitsei89]

11 hours ago, mk1980 said:

a bit late for a rule suggestion, but did you consider a rule/achievement that gives a %bonus if all launches use the same launch vehicle (same rocket up to the fairing that holds the payload. or same space shuttle / SSTO except for the stuff inside the cargo bay/cargo fairing).

in the real world, design of the launch vehicle is a big deal and it would seem likely that a space agency would try to use the same vehicle for launches of payloads with similar sizes.

judging from the teaser image posted by Laie, it looks like he's doing that already and i think that's a pretty cool little detail that should be rewarded.

i probably won't be able to use the same vehicle for all launches, though. strapping a plane on top of a rocket is usually a recipe for disaster...

That is already the most trivial and least time consuming way to do this... Just design a lifter capable of lifting your heaviest payload and use that for every launch. So that really isnt necessary rule..

 

But yeah. A nice challenge. Might try it

8 hours ago, AeroGav said:

What's the justification for that btw?   NERVs weigh 3 tons, if you can only use them for the outbound transfer burn there is no point using one at all.

I am not aware of a reason why a NERV should be any more difficult to restart than any other turbopump engine.   Though for the lunar module engine they  stuck to pressure-fed hypergolic engine because that engine had to work.

What I am aware of, is that the 800+ ISP ratings for NERV assume the use of liquid hydrogen, which is subject to boiloff - hence can only be used on the mars injection burn.

NERVs can also run off liquid ammonia, storable, non-sooting propellant,  but only get 600 or so ISP in this case.     I assume the existing stock chemical engines are running off "storable" propellants too since none get over 350 ISP whereas real chemical engines can already hit 450+ with liquid hydrogen.

So how about I do a mission with a NERV but declare it to be a "Liquid Ammonia" engine and so don't use the last 25% of the fuel in my tank, because the ISP of 800 in game is too high for that.       However,  I will use the engine for the return journey since it's running on a "storable" fuel source..

The stock system is already small/trivial enough to go anywhere without ions/NERVs...

[sevenperforce]

FYI - I added another bonus, A Solid Plan.

@mk1980 @Kergarin @Laie @AeroGav

17 minutes ago, tseitsei89 said:

That is already the most trivial and least time consuming way to do this... Just design a lifter capable of lifting your heaviest payload and use that for every launch. So that really isnt necessary rule..

Yeah, but it requires at least a little forethought, especially when it comes to docking, etc.

I only made it a low reward anyway.

17 minutes ago, tseitsei89 said:

But yeah. A nice challenge. Might try it

Thanks! I look forward to your entry.

17 minutes ago, tseitsei89 said:

The stock system is already small/trivial enough to go anywhere without ions/NERVs...

Exactly.

[tseitsei89]

@sevenperforce : Are design modifiers calculated like (A+B+C)*mainscore or like A*B*C*mainscore, where A, B and C are different design modifiers.

[sevenperforce]

1 minute ago, tseitsei89 said:

@sevenperforce : Are design modifiers calculated like (A+B+C)*mainscore or like A*B*C*mainscore, where A, B and C are different design modifiers.

mainscore*(1-(A+B+C))

Edited September 9, 2017 by sevenperforce

[tseitsei89]

4 minutes ago, sevenperforce said:

mainscore*(1-(A+B+C))

Ok forgot the (1-(Blaah)) but yeah I can work with this thanks

 

edit: this will probably take a while though... So many things to consider/optimize. So a good challenge I would say...

Edited September 9, 2017 by tseitsei89