How can I reenter safely

[hsnmck]

Hello,

I'm new to KSP and still trying to learn it. I'm not able to reenter safely, my parachute gets destroyed by aero forces and heat since I'm hitting the ground at 300m/s. Also while I'm reentering, the parachute icon is red. How can reenter safely without destroying my parachute and how can I slow down at reentry? Thanks. Edited November 21, 2015 by hsnmck
Change the prefix to answered

[ElWanderer]

What are you trying to re-enter with? From what orbit?

The usual advice for a pod returning from low Kerbin orbit is to set a periapsis of about 30km. You need the velocity to drop to around 250-260m/s before it's safe to pop the chutes. The early game is quite dangerous because it can be hard to get things to slow down. It's been reported that a mk1 pod with a heatshield is too heavy and aerodynamic to slow down effectively unless you reduce the amount of ablator during ship design. My current design carries about 30 instead of 200.

[sdrevik]

[quote name='hsnmck']Hello,

I'm new to KSP and still trying to learn it. I'm not able to reenter safely, my parachute gets destroyed by aero forces and heat since I'm hitting the ground at 300m/s. Also while I'm reentering, the parachute icon is red. How can reenter safely without destroying my parachute and how can I slow down at reentry? Thanks.[/QUOTE]

Are you coming in from Mun, interplanetary, or what?

Generally, the further you are coming in from, the higher your relative velocity to Kerbin. Dropping from Kerbin orbit is relatively slow, coming from Mun is faster, transferring from Jool or Moho is hella-fast. The faster you are, the harder it is.

First: get AIRBRAKES. Put four of them on your capsule. If you don't have it yet, do lots of science close to Kerbin and Mun so you can get it.

If you have any fuel left, burn retrograde and slow yourself down before you get < 60km.

Use heatshields. And turn ON the airbrakes. Put lots of external things in equipment bays so they don't explode, or on top of the capsule.

Engine systems make pretty good heat shields, too. Make sure you ship is pointing retrograde as you enter.

If you're coming in fast, dip down to between 40K and 50K, and if you get it right you'll slow down enough to orbit ,and you can make multiple passes to eventually slow down to get captured for full re-entry.

But coming back from other planets, leave yourself plenty of delta-V to slow down before you hit Kerbin atmosphere. Otherwise- boom.

[hsnmck]

Thank you guys, your suggestions helped. I'm not crashing anymore :)

[EditorRUS]

Many players seem to struggle with re-entry and it's not so far from reality, actually.
There are a couple of tips I can give.
First of all, all planets have certain critical height at which you can put periapsis without getting most of your crafts exploded. For Kerbin it seems to be around 30 km. Never put your periapsis lower than that if you are re-entering. If you are returning from orbit around Kerbin, you should stick to 30 km to 40 km. Exact safe altitude depends on your starting velocity upon re-entering. Getting back from interplanetary flight seems far more trickier and you should mostly find the value empirically. For most part it's not worth it to put it higher than 50 km, but it's too dangerous to put it at <40 km.
When re-entering, take a look at your craft and answer a question: "Does my craft have any heat-sensitive equipment which may get into the air flow?". If so than re-enter pointing nose forward, otherwise try to induce as much drag as possible by exposing more of your craft. If you have a heat shield, you should _always_ make sure it gets in the flow the most. Heat shields are very heavy and you should shrug off some of ablator since you won't need it anyway. Depending on your re-entering profile you might need up to 200 ablator for 3.5 m heat shield.
And you can open with right click parachute's menu which will state if it's safe to deploy it now. Unsafe will get your parachute destroyed immediately, risky might do that, safe will never lead to that.

[QUOTE]First: get AIRBRAKES. Put four of them on your capsule. If you don't have it yet, do lots of science close to Kerbin and Mun so you can get it.[/QUOTE]
DON'T. They are not designed for re-entry and most likely won't survive for long. Edited November 22, 2015 by EditorRUS

[sdrevik]

[quote name='EditorRUS']


DON'T. They are not designed for re-entry and most likely won't survive for long.[/QUOTE]

Meh, if I'm not coming in too fast, they survive just fine, and help bleed off more velocity / ensure capture. Generally, if they blow up, the whole ship is gonna blow anyway. I swear by them in all my designs.

[Chakat Firepaw]

[quote name='sdrevik']If you have any fuel left, burn retrograde and slow yourself down before you get < 60km.[/QUOTE]

Be careful when doing this, as it will also lower your periapsis. You may need to add some radial-out to keep from descending too far too fast, (a mod that adds flight info can be very useful here).

[GoSlash27]

The recommended workaround for this wasn't mentioned, so I'll post it here:
Attach the heat shield with a decoupler. Once you've gotten through the reentry heating and deceleration drops below 2 Gs, decouple the shield. You will slow in plenty of time to deploy chutes after that.

Best,
-Slashy

[Adm010]

I find that the droge shoots are pretty useful in slowing down before oping the main chute

[hsnmck]

[quote name='ElWanderer'][COLOR=#333333]
It's been reported that a mk1 pod with a heatshield is too heavy and aerodynamic to slow down effectively unless you reduce the amount of ablator during ship design
[/COLOR][/QUOTE]

[quote name='EditorRUS'][COLOR=#333333]
Heat shields are very heavy and you should shrug off some of ablator since you won't need it anyway
[/COLOR][/QUOTE]

[quote name='GoSlash27']
Attach the heat shield with a decoupler. Once you've gotten through the reentry heating and deceleration drops below 2 Gs, decouple the shield. You will slow in plenty of time to deploy chutes after that.
[/QUOTE]

I really like this workaround, it works well, thanks.

[Pecan]

1. Read any of the 'How to re-enter threads'
2. Laugh at some 'Re-entry impossible threads'
3. Try shallower.
4. If that doesn't work, try steeper (don't ask)

[Ulfstein]

If you put the heatshield on the nose of the cone instead of under it, the shield plus the cone immediately after it creates enough drag to brake efficiently, but it looks less realistic.

[sal_vager]

That's true Ulfstein, it's thanks to the shape of the drag cubes and the flat back in that configuration, though it looks awful.

[Willy101]

I just use drouge chutes, normal chutes and heat shields.

[Hodari]

All the posts about Pe height are technically correct, but may not be overly helpful for a brand new player.  Obviously, someone who doesn't even know how to reenter safely yet is NOT coming back from an interplanetary mission and it's entirely likely that haven't even reached a full orbit yet, so in that case they won't have a Pe.  If this is a suborbital flight that we are talking about here, then there are 3 important things to consider for reentry.

1.  Keep the mass of your reentry stage as low as possible.  The more massive it is, the harder it will be to slow down in time.  Early on, you'll probably want to only bring back the command pod, parachutes, heat shield, and whatever science instruments you can(be careful with the science jr. if you're trying to return that.)  You should definitely drop all your engines and fuel tanks before reentry.  And make sure you have enough parachutes for whatever craft you are using.  I normally find 2 radial mounted chutes will be much better than 1 regular mk16 and will probably be enough for most of my designs(more will be needed if I'm using something like the 2.5m command pod).

2.  Even if you're just going suborbital and don't have a Pe, it is still important to come in at a shallow angle.  Don't just go straight up and try to come straight back down again.  You should be trying to follow a similar ascent path to what you would use if you were going for a full orbital flight.  Going more horizontal during the descent means more air to slow you down(also means more time for your ship to be exposed to reentry heating, so at SOME point this becomes a balancing act, but especially if you have a heatshield, this won't be an issue yet.

3.  Make sure you keep the blunt end of your craft pointing forwards.  Again, you need the air to slow you down as much as possible.  If the top of your command pod is pointing forward, it won't slow down nearly enough.  Also, keep this in mind when designing your reentry stage in the first place.  Try to keep the center of mass of this stage as low as possible, close to the heat shield.  This is where the science jr. can be a bit of a risk since having it in between the pod and shield might make things less stable.  If your reentry stage is properly balanced, once you start reentry, you can usually turn SAS off altogether and just aerodynamics alone will keep it pointing the right way.  Also, if you do lose control of your ship and can't keep it pointing retrograde, the next best option is usually to keep it spinning/tumbling as fast as possible(might not be much fun for the poor kerbals trapped inside, but better than blowing up).  You lose the protection of the heatshield this way, but it will at least mean that it's constantly exposing different parts to the heat instead of keeping the same one there long enough to explode.  Obviously if you're going fast enough, this won't help much though.  Again, the one thing you usually DON'T want is for your craft to end up pointing prograde and getting stuck there since even if you survive the reentry heat, you probably won't slow down quickly enough.

And finally, the parachute turning red doesn't mean it's broken or anything.  It just means it's not safe to deploy it at that moment.  Once you've slowed down enough to safely use it, it will change back, so watch it closely.  If you still can't slow down enough in time, that's when drogue chutes might be useful, but you probably won't need those for a while.

[Warzouz]

On 22/11/2015 at 0:19 AM, sdrevik said:

First: get AIRBRAKES. Put four of them on your capsule. If you don't have it yet, do lots of science close to Kerbin and Mun so you can get it.

If you have any fuel left, burn retrograde and slow yourself down before you get < 60km.

Use heatshields. And turn ON the airbrakes. Put lots of external things in equipment bays so they don't explode, or on top of the capsule.

Engine systems make pretty good heat shields, too. Make sure you ship is pointing retrograde as you enter.

If you're coming in fast, dip down to between 40K and 50K, and if you get it right you'll slow down enough to orbit ,and you can make multiple passes to eventually slow down to get captured for full re-entry.

But coming back from other planets, leave yourself plenty of delta-V to slow down before you hit Kerbin atmosphere. Otherwise- boom.

Well, that's not very true...

1- Airbrakes were very efficient in 1.0.4. In 1.0.5 and 1.1.x, they will simply burn very quickly (< 5 seconds), except if you tweak their stats in the part file... Airbrakes aren't designed for atmospheric reentry.

2- Heatshield is not useful for reentry even from Mun. Kerbal-X has no heatshield and can totally reentry safely from Mun or Minmus. I'm not sure about the basic command pod, though. In any case, you can set a heatshield and remove ALL ablator, or at least keep less than 10%. That saves a lot of mass.

3- 50km Pe will let you heat without slowing down. Best periaps is around 30km (25 -30 if you're slow ; 30-35 if you come very fast > 4000m/s).

4- For interplanetary reentry, it largely depends on your return vehicle. Keep the reentry vehicle simple (pod, partial heatshield and chutes). You should test them and rate them (in m/s at 30/35km). Only Moho is dangerous to return from and you should prepare for slowdown before reentry. Even though a full heat shield is never useful. Direct reentry is always an option except for complex ships like SSTO

EDIT : stupid me, I didn't saw this was an outdated question, sorry.

Edited June 28, 2016 by Warzouz

[sdrevik]

Yes, re-entry is a lot more deadly.   You pretty much have to enter an orbit and lower the orbit before trying to re-enter.   I lost a lot of ships after the change by not having enough dv left to orbit Kerbin, and they just go sailing past... although it's fun to try to quickly build / launch, and rendezvous  a refueling vehicle from Kerbin as they fly by Kerbin so they can have more fuel for the next pass.   That's a rendezvous that MechJeb won't help you with very much, you really have to use a combination of math, eyeballing, and F9 to launch at the right time, match angles, and match speed.

[Targetedmissle]

Can anyone help me do this but from jool, i need help getting back to kerbin.

 

[Vanamonde]

3 hours ago, Targetedmissle said:

Can anyone help me do this but from jool, i need help getting back to kerbin.

 

Do you have the large inflatable heat shield? It should be able to handle the heat and forces for re-entering at Kerbin. What does your craft look like? 

[Bej Kerman]

On 11/21/2015 at 10:24 PM, hsnmck said:

Hello,

I'm new to KSP and still trying to learn it. I'm not able to reenter safely, my parachute gets destroyed by aero forces and heat since I'm hitting the ground at 300m/s. Also while I'm reentering, the parachute icon is red. How can reenter safely without destroying my parachute and how can I slow down at reentry? Thanks.

Use a heatshield and make sure your parachute is set to only deploy when safe./ Also, use drogue chutes to slow yourself down.

[jimmymcgoochie]

14 hours ago, Targetedmissle said:

Can anyone help me do this but from jool, i need help getting back to kerbin.

 

Direct returns from Jool are not recommended as you’ll be going extremely fast, try to brake into orbit or skim the atmosphere to aerobrake before re-entering; aerobraking will burn up a lot of ablator so the 10m inflatable heat shield is your best bet.

You can still do a direct re-entry coming back from Jool but things will get very very hot and you better keep those pods pointing exactly retrograde or they’ll cook pretty quickly.

All that is assuming you have re-entry heat at 100% or more, if it’s lower then just bomb into the atmosphere with reckless abandon and you’ll be fine. Probably.

[Targetedmissle]

I am using an SSTO

On 6/11/2020 at 6:49 PM, Vanamonde said:

Do you have the large inflatable heat shield? It should be able to handle the heat and forces for re-entering at Kerbin. What does your craft look like? 

 

[Vanamonde]

That's going to be tough, returning from Jool with a plane. I'd advise doing pretty significant braking burns with the engine. Then descend belly-first to maximize the drag that will decelerate you and thereby reduce the heat you sustain. Some parts are more resistant to heat than others, like the shielded docking port, but those won't help much because they fit to the frontal surfaces. 

[Spricigo]

14 hours ago, Targetedmissle said:

I am using an SSTO

Please, a picture. You need to post it somewhere and give us the link so we can see what are your tools for the job.

Generally speaking, you don't want to reenter with a craft that have low heat tolerance. If aerobrake/aerocapture is possible at all, you want a craft that can fly like a pancake to bleed out velocity quickly before diving into the low atmosphere.

Unfortunately, that is the kind of thing you need to take care way before the time of reentry. If you ended up in a plane that burst in flames just after touching the atmosphere then it's time to design a rescue mission.