Leave Nothing behind - Eve SSTS

[Tony Swallow]

Good morning all,

I'm playing a challenging Career. I have the following self-imposed Rules

-   NO mods. I'm using the full KSP1 updates including Breaking ground and Making history.

-  As Green as possible. Not leaving descent stages etc on the surface of visited bodies

-  Doing things as quickly as possible in game time. This makes it particularly interesting as I'm making ships that have high Delta V to do interplanetary missions so I can get there as quickly as possible without having to time-warp for days/weeks/months/years to get to optimum launch windows.

-  I'm allowing myself to test craft on a sandbox game before committing in the career.

-  I'm regularly saving and I do allow myself the luxury of reverting back to an old save if I lose some Kerbins, The fact that I have lost a week of realtime progress is the punishment for my neglect (So far I have only had to do so once).

So far I'm up to day 120ish and I've made a lot of progress. Tech tree is maxed out, Fueling facilities on the Mun and Minimus, Interplanetary ships on the way to Moho, Eve and Duna and the next interplanetary launch will be to Dres.  

Now the challenge that I've set for myself is the Holy Grail, EVE

Fuel is not a problem. I have refineries (The Eve interplanetary mission includes a refinery for Gilly) so I can burn fuel as required.

The trick is getting to the Eve surface, and back, without discarding stages which is a hard task.

The obvious answer is an Eve SSTO. It is possible, people have done it, but it's a very hard craft to get right.

The way I'm planning to get around it is to build an Eve Single Stage to Suborbital, and then "catch" the craft as it nears the Apoapsis  with another craft that is in Orbit.

What makes it hard is that the orbital Velocity at LEO is 3,200 m/s. The capture craft needs to do a rendezvous burn to match the lander, where the difference in speed will be massive, and then do an orbital burn. All this has to happen in minutes whilst the lander is above Eve atmosphere. The difference in velocity is huge, which makes for a huge capture ship. Assuming Zero orbital velocity of the lander at Apoapsis you over 6K Delta V.

A ship with 6K Delta V is easy enough. Liquid fuel and lots of Nerv's. But this wont work as you simply can't burn fuel quickly enough to get enough velocity change in the timeframe of minutes. So it has to be a Conventional rocket. But this has the problem of the tyranny  of the rocket equation whereby you just can't get 6K and have a fast enough burn to to the catch. The obvious answer is to discard stages but anything discarded will end up in a suborbital trajectory over Eve, which defeats the point of the exercise.

So now I'm working on a lander craft that is as optimised as  possible to get as close to orbit as possible. So far I have managed over 1K orbital velocity with the Apoapsis at 110km. My target is 2K, If I can get that then a "catcher" with a starting Delta V of 3K should be able to do it. and this should be achievable.....

WIsh me luck, If I can do It I'll post a mission report with Photo's etc.

 

 

[Vanamonde]

They said it couldn't be done! (And they might be right.) 

[Kimera Industries]

So by "no stages discarded" you are even counting objects that would burn up in the atmosphere?

[QF9E]

I've built an Eve SSTO a while ago: https://imgur.com/a/1AD3u40

Propellers are the best option for the lower atmosphere, then you will need lots of thrust to ascend to orbital altitude, and then you will need lots of dv. My craft used propellers to about 13 kilometers altitude, Vectors for the rapid boost to suborbital trajectory and NERVs to insert into Eve orbit. As to Vectors: The Mammoth is basically 4 Vectors but is 1 ton lighter than 4 Vectors so I think that is the best engine for an Eve SSTO.

[Kimera Industries]

5 hours ago, QF9E said:

The Mammoth is basically 4 Vectors but is 1 ton lighter than 4 Vectors

Interesting that it would be lighter. I never knew that.

[Tony Swallow]

On 1/23/2024 at 1:19 PM, Kimera Industries said:

So by "no stages discarded" you are even counting objects that would burn up in the atmosphere?

Yep, that the target! I Know I CAN build a lander that has disposal of stages. But I want to get a system that can do it without! This is for two reasons...

1 - Keeping in with the "Green" concept of not throwing away components to make landings

2 - The way I'm playing it will be a long time (in realtime) between sending ships to Eve. And there will be times when I transfer from a body other than Kerbin to Eve. If I can do it with an SSTS and catch-net then I can refuel the ships in orbit and do a landing, without having to send additional stages from Kerbin to reset. 

[Kimera Industries]

30 minutes ago, Tony Swallow said:

Yep, that the target! I Know I CAN build a lander that has disposal of stages. But I want to get a system that can do it without! This is for two reasons...

1 - Keeping in with the "Green" concept of not throwing away components to make landings

2 - The way I'm playing it will be a long time (in realtime) between sending ships to Eve. And there will be times when I transfer from a body other than Kerbin to Eve. If I can do it with an SSTS and catch-net then I can refuel the ships in orbit and do a landing, without having to send additional stages from Kerbin to reset. 

That makes a lot of sense for your goals, I can see that. I didn't think about the fact that a suborbital catch with no spent stages would let you reuse the lander.

[Tony Swallow]

On 1/23/2024 at 7:44 PM, QF9E said:

I've built an Eve SSTO a while ago: https://imgur.com/a/1AD3u40

Propellers are the best option for the lower atmosphere, then you will need lots of thrust to ascend to orbital altitude, and then you will need lots of dv. My craft used propellers to about 13 kilometers altitude, Vectors for the rapid boost to suborbital trajectory and NERVs to insert into Eve orbit. As to Vectors: The Mammoth is basically 4 Vectors but is 1 ton lighter than 4 Vectors so I think that is the best engine for an Eve SSTO.

Wow, thanks for Sharing! This is really appreciated! I've also been using propellers to "claw" as high in the atmosphere as possible! I've found that the performance of the has an abrupt ceiling, whereby they stop "working" and the speed (and nose) drop rapidly, within seconds. At I first tried a "straight up" lander which worked reasonably well, however getting it to re-enter without a heat shield (which is not 100% re-usable), proved impossible. So a spaceplane it is. How have you managed Power supply whist using props to get above the atmosphere? I have used a combination of batteries and Solar panels, where I get about 80% of the way up and then open the throttle and deplete the batteries,  aiming to almost drain them as the rocket engines kick in.

[Kimera Industries]

12 minutes ago, Tony Swallow said:

Wow, thanks for Sharing! This is really appreciated! I've also been using propellers to "claw" as high in the atmosphere as possible! I've found that the performance of the has an abrupt ceiling, whereby they stop "working" and the speed (and nose) drop rapidly, within seconds. At I first tried a "straight up" lander which worked reasonably well, however getting it to re-enter without a heat shield (which is not 100% re-usable), proved impossible. So a spaceplane it is. How have you managed Power supply whist using props to get above the atmosphere? I have used a combination of batteries and Solar panels, where I get about 80% of the way up and then open the throttle and deplete the batteries,  aiming to almost drain them as the rocket engines kick in.

Engine alternator could help out too for a bit. They're pretty powerful.

[QF9E]

14 hours ago, Tony Swallow said:

Wow, thanks for Sharing! This is really appreciated! I've also been using propellers to "claw" as high in the atmosphere as possible! I've found that the performance of the has an abrupt ceiling, whereby they stop "working" and the speed (and nose) drop rapidly, within seconds. At I first tried a "straight up" lander which worked reasonably well, however getting it to re-enter without a heat shield (which is not 100% re-usable), proved impossible. So a spaceplane it is. How have you managed Power supply whist using props to get above the atmosphere? I have used a combination of batteries and Solar panels, where I get about 80% of the way up and then open the throttle and deplete the batteries,  aiming to almost drain them as the rocket engines kick in.

My Eve SSTO uses fuel cells to power the props. The fuel cells do not consume a lot of propellants. I did try solar panels but I wasn't successful with them - too much of a hassle keeping them from burning up during Eve atmospheric entry.

I think a plane is better than a helicopter / drone, as the lift to drag ration of wings is way above 1. Which means that you need only a fraction of the thrust to propel a plane compared to a helicopter. Moreover, the Big-S wing and wing strake can store fuel as well, so you don't need as many fuel tanks, which also means that the mass penalty for using wings is not very high.

[EveMaster]

I did a fully recoverable mission to Eve and back in 2019 with suborbital docking. Mammoth engines are indeed the best option for this, because of the best thrust to weight ratio. Taking off from  the highest possible point is important to not waste fuel in the lower parts of the atmosphere. It is also important to have enough reaction wheels and RCS to be able to dock quickly before falling back into the atmosphere. Good Luck with this truly hard challenge!
 

My design will probably not work as good in the current version of KSP 1 because back then the weight of the Kerbals did not count to the total weight of the ship and the Crew cabin modules I used were also lighter.

[Tony Swallow]

Thanks QF9E for your suggestions on power. This has been a "head scratcher" for me. With this kind of mission there is the potential of having to "loiter" at altitude whilst the catch-net craft gets into the right position before the final run to sub-orbital for the catch. the idea of burning energy reserves whilst waiting is pretty unappealing  as this means more batteries, more mass etc for the sake of having wiggle-room before the final run. I did a lot of experiments with solar cells, working out the balance required to maintain  positive power whilst doing so. I wasn't to concerned about them burning up on re-entry as I could position them in a "safe" place. The obvious problem is drag and mass. Also solar cells work better the higher into the atmosphere you get. Which makes balancing tricky as you don't need as many solar cells to Loiter but getting to altitude in the first place either takes a long time or more batteries.

I gave your suggestion re fuel cells some thought and tried that. Using fuel cells, the mass cost of the extra fuel is more than offset by the savings that are made  by not having solar cells, and no drag from the solar cells is a bonus! Also less problems with energy management as they have a consistent output (as compared to Solar cells). In short it looks as though the best outcome for me will be a craft with Fuel cells.

I've managed to get craft into a solid Suborbital, and managed a simulated catch. But I want to optimise it and do a full "beginning to end" run before posting pics.

Edited February 1 by Tony Swallow