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Leave Nothing behind - Eve SSTS - Success!


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Good morning all,

A few weeks ago I posted a challenge for myself, That is building an EVE Single Stage to SUB-orbital, and catching it with a passing capture craft.

For a quick recap, I intend to use this in a Career game, with some 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. With ships with a 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.

Fuel is not a problem, I will have a refinery on Gilly to supply what I need.

So why an SSTS Over an SSTO? Making a Ship which is forgiving and flexible is important to me. I want to have a ship that can be used for any number of missions, apart form landing and planting a flag for experience. So if, for example, I got a mission to do a scan of Basalt I want to be able to put the arm in a storage can, land near a formation, attach the arm with an Engineer and complete mission. Likewise, I want to be able to launch at sea level. I want to fly away from the equator. An SSTS will (in theory) give me that robustness. Without having to make a bespoke craft for every mission

There are three craft involved in this mission. Obviously the SSTS itself, which will land.

Then there is the "Catch-net" craft, which has to have a high enough Delta-V to match the velocity of the SSTS in space, and do a burn to get it into orbit as well. For this it needs a high thrust to weight ration so the matching can be done quickly.

The final craft is the "Nudge" craft, which will be used to take the SSTS to Low Eve Orbit from the station (At 150km) and then retro burn to push the SSTS into the atmosphere.

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The "Catch-Net" craft, which has 6 mammoth engines, and lots of fuel (3740 Delta-V) It also has strong RCS and reaction wheels to enable a fast docking. It is set to orbit at 120km

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The "Nudge" Craft - A lot smaller!

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The SSTS docked to the Nudge Craft, ready to drop into Low Eve Orbit.

The nudge craft allows me to burn for a steep entry into Eve Atmosphere. From a stable orbit of 91km-92km I do a burn dropping the Periapsis to 45km! In the minute or so before entering the atmosphere I undock, turn it around and do a burn to Keep the "Nudge" craft in orbit. This has the dual advantages of having full tanks on the SSTS when it lands, as well as allowing for a harder burn which helps with heat management later. 

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The SSTS entering Eve Atmosphere, at the point where the heat load is greatest! The critical component is the FL-A215 Fuel Tank Adaptor which fails at 2,000 Kelvin. It maxed out at less than 1,950! A miss is as good as a mile. However the 1.25m to 2.5m adapter has a tolerance of 2,700K,which makes it far safer on re-entry, so the final craft may have that instead. Forgiving and flexible is the name of the game!

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The rest of the landing is pretty routine. I set down on the patch of land between between the Crater Lake and eastern sea. Obligatory Kerbins on the ground shot!

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I waited until the "Catch-Net" was approximately 180 degrees out of phase (ie, on the other side of the planet) before commencing my take-off and climb. I have used 2 rotor units (rotating opposite directions) with ducted fan blades in a 2.5m Service bay to power the craft to altitude. I have set the RMP at 400 and use the main trottle for torque and an action group ti incrementally change the fan blades. For Power I have two Z-4K Rechargeable Battery Banks for storage and 2 Fuel cell arrays (in the nose). I find that the weight of fuel used to get to altitude gives a better power to weight ratio than batteries or solar cells. However I still have solar cells that line the cargo bay (obscuring the propellers), and two batteries. This will enable me let the batteries fully charge and then do shorter "hops" across the surface. This is also why I've used two batteries instead of one, as it will more than double my rang for "hops" . The solar cells sit inside the bay, so no drag when they close(correct me if I'm wrong).   The total mass of the ship is a bit over 200T full of fuel.

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I'm using the distance to the "catch-Net" as a "marker" for determining when I start my burn into Sub-orbital. This was my 3rd attempt. 300km was too late, 600km too early. Lets see how I go for 480km

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I'm a lot lower than I would like! I should be starting at 15K+ But I start the burn anyway! See how it goes! A single action group turns off the rotors, closes the bay doors, retracts the blades, activates the Vector engines, retracts the flaps (in case I'd forgotten to do that). 

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Burning hard to get out! Note I've got the Shielded clampatron ready to open as soon as I exit the atmosphere! 

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I'm back on the "Catch-net". It's not great, but it's "workable" The SSTS is on it's way out and will peak at over 150km. I should have started my burn a bit later, say 450km. I can make an intersect using an Anti-radial burn on the "Catch-net".

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I've got an intersect. But I will be docking on the downward (wrong) side of the SSTS Apoapsis. This has the dual disadvantage of needing more Delta-V to keep it in orbit and a lot less time to dock and do the burn before hitting the atmosphere!

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GOT IT!

I have managed to dock! But now I'm in the atmosphere, no time for finesse, or to even get a decent screenshot! I turn the ship to somewhere between Anti-Radial and Prograde and open up with the engines!

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After some initial "by the seat of pants" flying I'm in orbit! with some fuel to spare!

Conclusions   

This was by no means an "optimum" flight! The burn started late, I couldn't intersect on the upwards trajectory, I almost ran out of fuel and I dipped into the atmosphere. However It worked! With some adjustment in the timing I will be able to get a much "cleaner" recovery, with enough fuel to get back to the Eve Station. I'm considering having the "Catch-Net" sit in a higher orbit. The compromise is one of having more time in sub-orbital outside the atmosphere and easier to adjust the SSTS flightpath for intersect, V's the timing and also the SSTS having fuel to actually make a burn to improve the intersect. 

All in all proof of concept which can be refined! I will be able to use this craft  in my Career game and know that I have "wiggle-room" in my flights that I wouldn't have with an SSTO.

On a final note there are about 10 minutes of the mission which are really intense! from when the burn from the atmosphere starts to when you have it back in orbit. I really enjoy the challenge of "flying by the seat of your pants" that this entails!

 

 

 

 

  

 

 

 

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6 hours ago, Tony Swallow said:

The "Catch-Net" craft, which has 6 mammoth engines, and lots of fuel (3740 Delta-V) It also has strong RCS and reaction wheels to enable a fast docking. It is set to orbit at 120km

I think these are Mastodons, actually.

Great mission! I wonder if Eve landing tourist contracts pay a lot. If you play in career, you may have a gold mine with them.

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On 2/5/2024 at 6:41 PM, Nazalassa said:

I think these are Mastodons, actually.

Great mission! I wonder if Eve landing tourist contracts pay a lot. If you play in career, you may have a gold mine with them.

Indeed, you are right, they are Mastodon's! It does the job! burning through 3000+ Delta V in about 60 seconds.

I've done a couple of repeats, to make sure it's not a fluke. I've found that one of the hardest things to balance is the rate of rendezvous approach. When I have all the time I need I approach slowly, with the last 200m or so at less than 10m/s. When doing this capture maneuver time is a major factor. So I have to discipline myself to go hard for the docking. I don't even have the time to set up maneuver nodes to do an optimum burn. Real Piloting!

I'm not too sure how much tourist contracts to Eve pay. Once set up I'm not disposing of parts so I can refine fuel and repeat as many times as I want. So yes, A lot of potential profit in the pot. On the other hand the way I've been playing is that I've completed a lot of Kerbin/Minimus/Mun/Sol orbit tourist contracts so I have a really deep pockets. It's been a while since I've had to "watch the cost" on any given ship

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