magnemoe

Solution to aerobraking huge ships.

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I have long had problems aerobraking huge and heavy ships. Airbrakes help but is of limited use same with large fins from wing parts with control surfaces, going to low and ship will tumble.

So I started thinking, I have an huge plate in front generating lots of air resistance so I need another plate in the bottom, obvious solution was an base plate made of wings.

TFUZ3EFl.png

From back
UtTxqkjl.png
The H bars are to land on, yes its many of them but had problem with ship exploding on launch pad. 

Aerobrake is rock solid, even deorbiting the ship is solid, as an bonus mechjeb landing predictions give good data letting me brake directly into LKO.
Not sure if this is well known but it changes how I operate. As an added bonus I think I can upgrade existing ships to some degree with structural plates and KAS, perhaps even dock to rear docking port but that would easy cause problems for engines and landing legs. 
 

 

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Humm... this would work for me. And, like the heat shield, I could jettison the plate after the fiery re-entry is over. Great idea, thank you.

Eve, here we come.

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Or you could put another heatshield at the back just to act as a drogue. 

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26 minutes ago, Foxster said:

Or you could put another heatshield at the back just to act as a drogue. 

It would work well for stuff like Eve landings, not for an tanker in the Minmus-LKO run. 
It can not drop stuff and it has to land and do burns. 

Note that it don't have to be wings, you however want an huge bottom of craft who create drag, think stuff like ore containers should also work.

And as the ferret says to the cat, you can drop it, this will flip your craft so you can drop the heat shield to or you can use it for airobrake an ship at eve who are going to gilly, here you would drop shield and plate after aerobrake, again the engine bonus, in this case you might want radial decoplers on drag plate (tm) so you can drop it and still use the engines for an gilly intercept. 

 

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1 hour ago, Foxster said:

Or you could put another heatshield at the back just to act as a drogue. 

I've tried that for an Eve lander but even with four heat shields in the back the stable orientation was still at a weird angle that left some stuff unshielded.

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I use multiple shields, 

efnL8vK.png

placed so that drag keeps the ship properly oriented even when loaded with cargo. 

6t9EDWR.png

 

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30 minutes ago, Vanamonde said:

 

efnL8vK.png

Cool design!!!

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7 hours ago, Vanamonde said:

I use multiple shields, 

efnL8vK.png

placed so that drag keeps the ship properly oriented even when loaded with cargo. 

6t9EDWR.png

 

smart. bonus for extra shielded area. I would put the rear shields a bit down, mostly as you could land the ship on minmus 

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8 hours ago, Vanamonde said:

I use multiple shields

That is clever, especially putting the additional modules under the shields. At first, I was wondering about the weight/(cost) differences between a winged 'drag plate' vs the shields... until you revealed beneath.

I'm going to have to explore both ideas. :)

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Rather than a drag plate, I've been experimenting with a wing design to keep me facing the right way during Eve entry.

obvs4t4.png?1

This one didn't actually work as the moment was still too small, but I don't have a pic of my latest version which does work, is longer, and has an ISRU and drills just behind the heat shield, which coupled with not a lot of fuel on board keeps the centre of mass nice and low.  It's scary just how much force you need to keep straight braking in to Eve from a low orbit. 

Obviously this isn't going to give me as much drag as the OP's design, but it's a lot easier to launch from Kerbin as the box wing segment is attached via a docking port so be launched low down on a separate launcher and docked later.  The rest of the ship can then hit LKO as an SSTO 

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On my last eve-mission, I put one of the inflatable heatshield at the front of my craft, one at the top, and that made my ship spin so fast that no part over got hot enough to explode :cool:

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It works with field modified crafts to. 
m0XOF9sl.png
The plates was added on Minmus. Produced with OSE workshop and added with KAS

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Fast update on this, even if the drag plates has worked very well for high speed re-enter from Minmus or even peak into solar orbit,

it failed catastrophically during the simulations of the Duna hard-brake scenario. 
Requirements was as follow, 3Km/s aerobrake around Duna with less than 1km/s cost of entering Ike orbit afterward. 
in this setting multiple shields work perfectly. peak G was 5, you will need autostrut for to avoid back shields to fold. 

Extra shields are skipped to Minmus to be added, major issue is that time is of an essence window does not wait. However 2Km/s at LKO can get you to Minmus orbit in 2 days

Thanks to Vanamonde who saved me an lot of time trying to get this right. 

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These are all solid moves, but don't forget to generally design as much weight as possible forward (toward your heatsheild). This usually means the engines and ISRU, which on an Eve ascent module is no problem, but gets more complicated for complex Jool/Laythe aerocapture schemes.   I also usually use a shallow tank right at the heatshield to consolidate residual fuel as far foreward as possible. 

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My solution is to just put a 10m heatshield on front and back.  That way, it doesn't really matter where the mass is-- whichever end has the CoM closer to it will end up being :prograde: during aerobraking.

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5 minutes ago, Snark said:

My solution is to just put a 10m heatshield on front and back.  That way, it doesn't really matter where the mass is-- whichever end has the CoM closer to it will end up being :prograde: during aerobraking.

That's so ugly though, rite? I cant bring myself to such means. 

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Aerobraking efficiency has much to do with how much you want to game the KSP aero/heating model, most notably the fact that vessels are transparent to drag when it comes to surface attached stuff. Simply packing in surface attached stuff (into a location fully protected from heat!) is by far the most effective way to shift the center of pressure, for example when I don't feel like being realistic I just shove lots of radiators into a service bay, for drag-on-demand.

Another fun fact is that nozzle exhaust only needs a pinhole to pass through, so you can essentially make heat-shielded engines by overlapping heat shields in a way that leaves a pinhole for the exhaust. Not only that but if you want to to even crazier with the exploiting, engine exhaust is only blocked by the OUTSIDE of a part, if you place an engine (like a vector) so that its nozzle is INSIDE a heat shield its exhaust can still exit through the heatshield: the result, a heat shielded engine that is still able to fire! Suffice to say this technique is stupidly good for aerobraking.

So in KSP it's easy enough to make fantastically well shielded craft, which go in the direction you want, and even with discretionary drag if you like so you can launch them as SSTO from Kerbin/Laythe. Doing so in a way that is realistic is another matter entirely though one can try to rationalize things likes engines offset inside heat shields, since real craft have had holes in heat shields for thrusters.

Edited by blakemw

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7 hours ago, Pthigrivi said:

These are all solid moves, but don't forget to generally design as much weight as possible forward (toward your heatsheild). This usually means the engines and ISRU, which on an Eve ascent module is no problem, but gets more complicated for complex Jool/Laythe aerocapture schemes.   I also usually use a shallow tank right at the heatshield to consolidate residual fuel as far foreward as possible. 

This is true but its not always practical if you want to land the ship, the 10 meter shield has to stay on top if you only use one. 
My drag plate was designed for reusable ships who can land. 

On the other hand I did plenty of mistakes on my Duna ship.
QvhdLrGl.png
heat shield an science lander and an huge tank for kis parts, then the 100 ton base and an lv-n pusher stage.

Yes, i should put the lander and the tank at bottom. I wanted to land on Minmus to fuel up so I put them on top but I could dock in orbit. 
I could also put an 10m shield on bottom of the pusher stage 

In the image I did not use autostrut, that did not work well, with struts if worked very well. 

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10 hours ago, Pthigrivi said:

That's so ugly though, rite? I cant bring myself to such means.

I dunno, seems to me that except for streamlined atmospheric-flight ships, pretty much all spacecraft are ugly, ungainly concatenations of hardware.  It's part of their charm, at least to me.  :)

What I can't abide is stupid looking, but "ugly"?  Gimme.

Anyway, here's an example of fore-and-aft heat shields that I put together a year or two ago.  It's a ship that's built around the largest-size 5m tank from SpaceY:

mRTaeAj.png

Designed to bring several hundred tons of fuel from Mun or Minmus to LKO, then go back for another load.  Works great, rock-solid stable, and I'm fine with the looks, myself.

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*Winces* 
Haha jk thats not bad. I feel like the splayed out engines would irk me though? What we really need is a stock ballute to offset the drag.


global_aerospace_ballute.jpg

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Quick question, on a ship that you reuse a lot, is there a way to recharge the ablation material?

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48 minutes ago, cephalo said:

Quick question, on a ship that you reuse a lot, is there a way to recharge the ablation material?

There is no stock way to transfer ablator that I know of.

Personally in your shoes, I would make a modular set up with a docking port between the ship and the heatshield, then swap out a fresh one when ever you are refitting. Obviously you may need some kind of infrastructure for it, like an "orbital forklift" at your station. Or just a rack where you keep the spares, and then you nose the ship up to the new one after discarding the used?

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1 hour ago, Pthigrivi said:

I feel like the splayed out engines would irk me though?

Actually, I liked 'em on that ship.  When they're all running, the exhaust plumes (with the slight outward flare) looked pretty cool, like a fountain.

1 hour ago, cephalo said:

Quick question, on a ship that you reuse a lot, is there a way to recharge the ablation material?

Nope, ablator can't be transferred.  It's why I like using the inflatable heat shield, since it doesn't have any ablator so it's 100% reusable.

It's worth noting that even the ablative heat shields actually do a pretty good job even without any ablator.  They're reasonably well insulated (don't transfer heat rapidly), and have a really high temperature tolerance (natch).  Yes, they work better with ablator, and if you're trying to bleed off multiple km/s of speed after a high-energy interplanetary transfer, then sure, you'll want ablator.  But for a Mun/Minmus milk run, or even a Duna/Kerbin shuttle?  I expect they'd be just fine even without the ablator.

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