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Reinhart Mk.1

Slowing down in an SSTO

Question

So much like my whole Eve adventure im having some trouble on rentry to Kerbin, just to spare everyone with the giant list of details for this mission ill break it down: I just got back from the Juul system but im currently going 4000mps upon rentry and while i COULD just let the ship be destroyed and parachute to the ground... well that hardly seems classy. I KNOW there's ways to slow down your orbital speed before actually encountering Kerbin but all my attempts just seem to end up in gravity assists that seem to ramp my speed up (accidental gravity assist?). Help?

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5 hours ago, Dale Christopher said:

@Reinhart Mk.1 post your spaceship! The community must save you! 

It's not just the craft. It's also the way he's trying to aerobrake.

@Reinhart Mk.1 if your current aerobraking method is anything like what I saw in that recent video, that's not the way to do it. You don't go tail first and lock retrograde. Instead, you go nose first, pitch up to ~30 degrees and let those wings work.

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23 minutes ago, Atkara said:

if your current aerobraking method is anything like what I saw in that recent video, that's not the way to do it. You don't go tail first and lock retrograde. Instead, you go nose first, pitch up to ~30 degrees and let those wings work.

lol no the reason i did it like that last time was because the mk.1 cockpit was always overheating, but yeah i just refueled it and just recaptured and it ended up fine! tbh i think i would've been perpetually stuck out there if i didn't refuel so the problem still isn't technically solved for me. i still love this community for always being helpful and responsive :P

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MK1 cockpits are the absolute worst possible noses you can put on an SSTO. They have extremely low heat resistance, and the nose gets some of the very worst heating (even if you try reentering backwards).

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5 hours ago, Reinhart Mk.1 said:

...so the problem still isn't technically solved for me.

We still haven't seen your craft, we have no info on it's fuel reserves/remaining dV and we don't have a save with the craft (ideally) halfway between Jool and Kerbin. Without these, all we can do is chit-chat :) 

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8 hours ago, bewing said:

MK1 cockpits are the absolute worst possible noses you can put on an SSTO. They have extremely low heat resistance, and the nose gets some of the very worst heating (even if you try reentering backwards).

Ya, the MK1 needs careful design and flight profile to work. The only design for more than LKO re-entry I saw actually used canards as a heat shield! The inline cockpit works much better (and allows a forward fuel talk for COM alignment)

That said I wouldn't call the MK1 the worst SSTO nose. I would say that would either be an open node or the MK2 cockpit.

Edited by ajburges

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4 hours ago, ajburges said:

I would say that would either be an open node or the MK2 cockpit.

What's the problem with Mk2 cockpit?

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What bewing suggested can be done of course, only if your quicksave is miles away from a lunar interception.

If your plummeting into the inner solar system from Jool you can intercept the Mun and use precise node mod to fine tune so the slingshot makes you hit the atmosphere while losing 100+ m/s or so.

But you have to intercept the mun from the proper angle to have a effect.

Question: which parts heat up?

If it's a specific part then perhaps you can shield it by aerobraking in the atmosphere at a specific angle. I know many parts heat up more if they're exposed to a greater frontal cross section. That means that a cockpit nose heats up more if it hits the atmosphere at a attack angle. That is what you would want to slow down. However, if it doesn't have enough stopping power using to little wings the part may overheat.

You can do 2 things. pitch and roll while going through the lower atmosphere your aiming for to actuate the vessel in a spin roll to distribute the heat blast over all cross sectional areas. This means you wont have as much stopping power but you will be able to dive in deeper. Best is to use a attack angle and as soon as the heat bar reaches near max you start rolling and pitching.

Or... you can activate spoilers on the elevons as soon as the heat bar reaches max and just keep the nose pointed to prograde and use the spoilers as airbrakes to decelerate. This might not be calibrated and lift balance might tumble the vessel, but that should actually be helpful as that would make the vessel actuate automatically and help stopping.

The most stopping power while expending Delta-V is when your are closest to Pe with the oberth effect. So if you use the tumble technique and your well inside the atmosphere and you happen to roll in relation to retrograde from time to time then try to use Z and X keys to quikly full and stop throttling when the nose is near retrograde as that would give the most stopping power.
Since you'd couple a deeper dive made possible by tumbling, activated spoilers and retro burns near pe in case the nose happens to tumble the proper way then it might be enough to capture into a orbit.

If only a few m/s extra are necessary you can always EVA and push the vessel, it may take to much time but it's always doable. Just rotate the vessel flat body to retro grade and EVA push the vessel facing towards kerbin on the Center of Mass.

If any of the steps are not reproducable you can fuel flow any left over monoprop or liquid fuel to stabilize the vessel.

 

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On 7/10/2019 at 8:34 AM, sh1pman said:

What's the problem with Mk2 cockpit?

Mk2 parts have excessive drag for their volume. On top of heat tolerance issues, they also are draggy and move your COL and  COP forward.

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