Is Mk1 cockpit useless for shuttles?

[tarkhil]

Hello

I've tried several times to do a re-entry with a Slim Shuttle from stock ships (with some modifications not affecting re-entry). Each time Mk1 overheats and expoldes.

Is it an intended feature, unitnended bug, or silly me unable to do right profile?

[AeroGav]

Inline cockpits are much hardier, i imagine the mk1 inline would do much , much better.

Other factors that help, from a craft design standpoint

• more wing area = more lift, don't fall into deeper atmosphere till later
• deployable drag also helps, eg. lowering landing gear and opening any service bays you have

From a flight profile point of view, if overheating is your first concern, pitch up to nose 20 degrees above prograde marker, you'll stay up more and slow down faster.

If you're trying to actually reach KSC, I did a video on that very thing (with a mk1 inline cockpit, no less)

edit - i forgot to say, less mass also helps.  ie. coming back empty means less kinetic energy to turn to heat on the way back.  

Edited January 10, 2017 by AeroGav

[Aegolius13]

It's not the best part for reentry certainly,  but it should be possible to survive if treated very carefully.  Are you coming in from a very low orbit?  I would get as close to 70x70km as you can first.   

Are you pitching up a lot as you reenter?  That should take some stress of the nose.

The total mass of your ship also plays a factor (the bigger the ship, the more kinetic energy is being dispersed as heat).  This part may be just unusable with big enough ships. 

@AeroGav says,  the easiest solution may be to change to the in-line cockpit and put a shock cone or other high temp part in front. 

[ForScience6686]

When it comes to shuttles and space planes I prefer steep re entries.  It makes targeting the runway easier IMO, and takes less time.  I burn prograde above the ocean wrapped by the continent west of ksc (if that made sense), return to prograde and enable sas.  From there it's hands off until below 35km and 1500 m/s, then adjust for approach bringing me to about 1 km at about 5 km out.  This method reduces the amount of time that your craft is soaking up heat and gets you into the thicker air to slow down faster.  If you come in too high, roll over and pull up to point towards the ground.  Having the wings greatly increased your drag profile which makes these types of landings possible.  However if you're still really heavy you'll need to burn further east to give more time to slow down.

[bewing]

Among spaceplane builders, you will get this argument about shallow vs. steep reentries. I'm in the shallow camp. If you have your Ap at 71km and set your Pe at 68km, and aerobrake gently, I think you can bring almost anything down to the surface, with a few exceptions. Setting your Pe to 0km makes it a race between heatsploding and slowing to below 1300 m/s. The one thing you really can't do is be wishy washy about it and set your Pe to something in the middle -- you'll die every time, then. But if the nose really is too sensitive to reenter, then your only alternative is a little bit of retrograde burning. If you slow to 1500 m/s then you can reenter anything.

[ForScience6686]

17 minutes ago, bewing said:

Among spaceplane builders, you will get this argument about shallow vs. steep reentries. I'm in the shallow camp. If you have your Ap at 71km and set your Pe at 68km, and aerobrake gently, I think you can bring almost anything down to the surface, with a few exceptions. Setting your Pe to 0km makes it a race between heatsploding and slowing to below 1300 m/s. The one thing you really can't do is be wishy washy about it and set your Pe to something in the middle -- you'll die every time, then. But if the nose really is too sensitive to reenter, then your only alternative is a little bit of retrograde burning. If you slow to 1500 m/s then you can reenter anything.

I actually set my pe well below 0, usually having the trajectory enter the ocean near the islands just off the coast of ksc.  This does call for a bit of fuel to De orbit though.  I prefer it to guarantee I make the runway, that's the big reason for me using this method.

[Kerbart]

The bottom part is extremely heat resistant but if you're building a shuttle around it than that's the part that does not get exposed to heat. The sidewalls of the cone might indeed not be that heat resistant, to "promote" re-entry blunt-end first.

[AeroGav]

I did enable the thermal data in action menus a few times (option in the alt f12 menu) and just got more confused.

There's a lot of factors at play.   In an inline cockpit,  because the front end is protected by modules ahead of it in the stack, heat flow is minimised by flying directly prograde - in the short term.  Pitching up exposes more of it to the air flow.

Of course, in the longer term, staying prograde makes you plunge deeper into the atmosphere and doesn't shed speed, you can run into a skin temperature limit when you plunge below 20km still going orbital velocity.

Using the wings to stay high slows down heat transfer and is easy on the skin temp, but due to the prolonged re-entry the core of the part can heat soak due to heat coming inward from the skin.

On the other hand, heat flows out as well, as the core gets hotter this outward transfer speeds up, and you can achieve an equilibrium even though the part is yellow hot.  Especially if the rate of inflow is quite low because you're high.

Finally you can start trying to work out what parts to attach to cockpits to help them cool off.  Wings and jet engines seem to make good radiaitors.

It gets very complicated when you drill into it.

[GoSlash27]

The trick to using Mk1 parts for SSTOs is aggressive aerobraking. Get the plane slowed down so quickly that it doesn't have the chance to overheat.

Yes, the low heat tolerance of Mk1 cockpits is intentional. They're not intended for space planes, just atmospheric flight.

Best,
-Slashy

Edited January 11, 2017 by GoSlash27

[Spricigo]

2 hours ago, GoSlash27 said:

Yes, the low heat tolerance of Mk1 cockpits is intentional. They're not intended for space planes, just atmospheric flight.

To make things worse often the mk1 command pod outperform it. 

[bewing]

1 hour ago, Spricigo said:

To make things worse often the mk1 command pod outperform it. 

Always outperforms it, in fact. The command pod is lighter, has less drag, and has better heat tolerance.

[tarkhil]

Thanks a lot! I've managed to return shuttle safely. 

[AeroGav]

15 hours ago, bewing said:

Always outperforms it, in fact. The command pod is lighter, has less drag, and has better heat tolerance.

...and horribly squishy.  I prefer at least a 3 star Kerbo-NCAP rating

 

[WanderingKid]

On a side note, I was having the same problem you were until I started sticking a radiator on top of the Mk1 right behind the cockpit on top, away from the heat.  That solved 95% of the problem.  A slightly higher Periapsis did the rest.

[foamyesque]

On 2017-01-10 at 2:32 PM, bewing said:

The one thing you really can't do is be wishy washy about it and set your Pe to something in the middle -- you'll die every time, then.

That ain't true. As long as you can maintain a stall you can reenter damn near anything with a periapsis of 45km on Kerbin. Shallow reentries just waste a bunch of time pulling your periapsis down to a point where you break at a reasonable rate, and heat-soak vulnerable parts like cockpits while they're at it, and steep ones exceed your skin tolerances and potentially g-loading as well.

45 degrees AoA, 45km periapsis. Works great.

My guess is he's not managing to keep the AoA up.

[Wanderfound]

On 1/12/2017 at 8:47 PM, foamyesque said:

That ain't true. As long as you can maintain a stall you can reenter damn near anything with a periapsis of 45km on Kerbin. Shallow reentries just waste a bunch of time pulling your periapsis down to a point where you break at a reasonable rate, and heat-soak vulnerable parts like cockpits while they're at it, and steep ones exceed your skin tolerances and potentially g-loading as well.

45 degrees AoA, 45km periapsis. Works great.

My guess is he's not managing to keep the AoA up.

Yup.

Cobra-style it; you can come in easy if you do it nose-up.

 

 

 

 

 

Less-stable ships may need to keep the pitch down a bit lower to maintain yaw stability, but the theory is the same. Just keep the nose up until your vertical speed settles down to a comfortable rate.

Edited January 13, 2017 by Wanderfound