How to get into eve

[Luc1fer]

So I’m sending a satelite, i barely can reach the planet (Ima always short of fuel) and when I entry no matter how many heat shields I stack the probe gets obliterated by the heat.

Can someone give me some advices and show me your designs?

thx beforehand

[Gargamel]

post a pic of the probe you got, and we can help there too.

Try building a bigger ship for the orbital insertion burn, then release the lander probe separate.  Then you can have a smaller lander, that requires less heat shields. 

[strigon]

Yeah, we're going to need a lot more than this.

Some basic tips, however, are to make things as light as possible. You don't need dozens of batteries and the biggest solar panels, for instance. Heat shields are quite heavy, so that might be part of your problem. It also took me a while to seriously consider engine weight; many times, a smaller engine - even if it's less efficient - will get you much further. A simple probe core, with a decent antenna, and a full science package with the half-sized 1.25 metre tank and the "Terrier" engine can make it to Eve from LKO, I believe.

As far as entry, go for a shallow approach. I don't often land at Eve, but 40-50 km is probably the lowest I'd go. If you have to make another pass to actually land, so be it. Aerobraking is notoriously dangerous.

Another tip you might like to use is what's called asparagus staging, or onion staging if you can't make that work.

 

And, just to make sure, how are you transferring to Eve? Are you waiting for a transfer window? Are you leaving Kerbin's orbit and then trying to force an approach? Walk us through what's happening. Because, at a guess, you're either not launching at a transfer window or brute-forcing your approach, wasting a ton of fuel, and resulting in a ridiculously fast approach. So you either run out of fuel, or come flying in so fast your whole craft disintegrates.

[Dman979]

Moved to Gameplay Questions and Tutorials.

Try entering at a shallower angle, and maybe making more than one entry into the atmosphere.

[OhioBob]

Make sure your entry vehicle has a low ballistic coefficient.  That is basically mass per unit area of heat shield.  For aerocapture I'd recommend a periapsis of about 60 km, though that will vary depending on the ballistic coefficient and the entry velocity.

[Kesa]

8 hours ago, Luc1fer said:

So I’m sending a satelite, i barely can reach the planet (Ima always short of fuel)
 

For the efficient trajectory part, do you know about :

1. Hohmann transfer
2. Launch Window
3. Oberth effect

You need to know about all three of them. It's completely possible to brute force your way any where in the Kerbol system using nuclear engines, but knowing how to do it the efficient way will teach you a lot of things, along which :

1. What is Delta V
2. How to read maps (search for ksp maps)
3. how to plan ahead and to know in advance what your vessels are capable of

As for the craft goes, go bigger. But do it smart. If you just scale up things, it won't work. Go bigger means add more stages with good proportion. Some rules of thumb I use to make an efficient rocket :

1. Minimize the playload mass. The size of each stage influence the previous one linearly. The difference between a 450 kg and a 900kg playload may not seem big compare to the mass of a rocket, but the 900kg playload will need twice as big of a launcher as the 450 kg playload. So don't bring anything you don't need.
2. Mass ratio between two stages should around 2.5-3. Just to be clear, this is the total mass of the craft at the ignition of a stage divided by the mass when the stage is ditched. If mass ratio is to small, you are likely staging too often, which implies you carry to much mass in engines and decoupler. If mass ratio is too big, you are suffering the tyranny of the rocket equation (dimishing return of additional fuel in a stage)
3. Adequate engines : adequate thrust : initial Thrust to Weight Ratio of about 1.4 -1.8 for ascending from a heavy body, acceleration of 4-15 m.s^-2 for space bound transfer burns. If thrust is too high, you are probably carrying too much engine mass. If thrust is too low, some manoeuver might be inefficient, or even impossible.
4. Adequate engines (bis) : adequate ISP some engines are better in atmosphere, some are better in vacuum. Some engines are poor reguarding both thrust and ISP, they generally only offer increased manoeuvrability and should not be fired for extended period of time (eg RCS thruster)**

When all that is done, fly your rocket. if it is short on fuel, add a stage, usually aninterplanetary one, and resize launcher accordingly. Other solution : do several launch and refuel missioins (needs you to know how to rendez vous and dock).

*acceleration divided by gravity. For Kerbin,g  = 9.81 ~10 m.s^-2. Acceleration is given in flight in the vessel info on the map view

**technically, it's more efficient to use the stages with worse ISP first, but you should not be carrying enough of poor ISP engines/fuel in the first place. Still good to know if you are very tight for some reason that you should first empty your monopropellant tanks to maximize your chances.

Quote

and when I entry no matter how many heat shields I stack the probe gets obliterated by the heat.

I guess your aiming directly at EvE. Don't. Even in order to land on an body without atmosphere, you want to decelerate as horizontally as possible, in the same fashion and for the same reason as for a gravity turn. When transferring from and interplanetary orbit, you can't expect to land in one aero brake. the first aero brake should be with a periapsis high enough so that your craft does not burn and low enough so that you get captured. If both condition can't be met at the same time, prefer the first and meet the second with a breaking burn at periapsis.

Then several braking passes may be necessary to slo into a circular orbit.

If your craft has fragile (low skin heat temperature resistance) components outside of a protective bay, be sure to have a heat shield strictly bigger than the craft.

Edited May 28, 2018 by Kesa

[blakemw]

Feathering is consistently effective at Eve, a small scale example which I built for 9000m/s entry at Eve:

It scales up well too. This rather exploits the fact that the game's drag model is too simplistic for hypersonic speeds, even stuff which should be in the wake of the capsule still generates full drag. So basically you can just add lots of these kind of flat pieces (spaced apart) to get as much drag as you like.

[MechBFP]

You should have no problem getting a small probe there with enough Delta V to burn into an orbit without even aero capturing.

Make each stage as small as possible, so your first stage should be a probe with say Oscar tanks and a tiny engine, then the next size of tanks with the next size engine, and so on until you get to the biggest engine you have. Then add a bunch of boosters to it as the final stage and you should have more than enough DV. 

[Luc1fer]

11 hours ago, MechBFP said:

You should have no problem getting a small probe there with enough Delta V to burn into an orbit without even aero capturing.

Make each stage as small as possible, so your first stage should be a probe with say Oscar tanks and a tiny engine, then the next size of tanks with the next size engine, and so on until you get to the biggest engine you have. Then add a bunch of boosters to it as the final stage and you should have more than enough DV. 

 

13 hours ago, Kesa said:

For the efficient trajectory part, do you know about :

1. Hohmann transfer
2. Launch Window
3. Oberth effect

You need to know about all three of them. It's completely possible to brute force your way any where in the Kerbol system using nuclear engines, but knowing how to do it the efficient way will teach you a lot of things, along which :

1. What is Delta V
2. How to read maps (search for ksp maps)
3. how to plan ahead and to know in advance what your vessels are capable of

As for the craft goes, go bigger. But do it smart. If you just scale up things, it won't work. Go bigger means add more stages with good proportion. Some rules of thumb I use to make an efficient rocket :

1. Minimize the playload mass. The size of each stage influence the previous one linearly. The difference between a 450 kg and a 900kg playload may not seem big compare to the mass of a rocket, but the 900kg playload will need twice as big of a launcher as the 450 kg playload. So don't bring anything you don't need.
2. Mass ratio between two stages should around 2.5-3. Just to be clear, this is the total mass of the craft at the ignition of a stage divided by the mass when the stage is ditched. If mass ratio is to small, you are likely staging too often, which implies you carry to much mass in engines and decoupler. If mass ratio is too big, you are suffering the tyranny of the rocket equation (dimishing return of additional fuel in a stage)
3. Adequate engines : adequate thrust : initial Thrust to Weight Ratio of about 1.4 -1.8 for ascending from a heavy body, acceleration of 4-15 m.s^-2 for space bound transfer burns. If thrust is too high, you are probably carrying too much engine mass. If thrust is too low, some manoeuver might be inefficient, or even impossible.
4. Adequate engines (bis) : adequate ISP some engines are better in atmosphere, some are better in vacuum. Some engines are poor reguarding both thrust and ISP, they generally only offer increased manoeuvrability and should not be fired for extended period of time (eg RCS thruster)**

When all that is done, fly your rocket. if it is short on fuel, add a stage, usually aninterplanetary one, and resize launcher accordingly. Other solution : do several launch and refuel missioins (needs you to know how to rendez vous and dock).

*acceleration divided by gravity. For Kerbin,g  = 9.81 ~10 m.s^-2. Acceleration is given in flight in the vessel info on the map view

**technically, it's more efficient to use the stages with worse ISP first, but you should not be carrying enough of poor ISP engines/fuel in the first place. Still good to know if you are very tight for some reason that you should first empty your monopropellant tanks to maximize your chances.

I guess your aiming directly at EvE. Don't. Even in order to land on an body without atmosphere, you want to decelerate as horizontally as possible, in the same fashion and for the same reason as for a gravity turn. When transferring from and interplanetary orbit, you can't expect to land in one aero brake. the first aero brake should be with a periapsis high enough so that your craft does not burn and low enough so that you get captured. If both condition can't be met at the same time, prefer the first and meet the second with a breaking burn at periapsis.

Then several braking passes may be necessary to slo into a circular orbit.

If your craft has fragile (low skin heat temperature resistance) components outside of a protective bay, be sure to have a heat shield strictly bigger than the craft.

 

13 hours ago, OhioBob said:

Make sure your entry vehicle has a low ballistic coefficient.  That is basically mass per unit area of heat shield.  For aerocapture I'd recommend a periapsis of about 60 km, though that will vary depending on the ballistic coefficient and the entry velocity.

 

15 hours ago, Dman979 said:

Moved to Gameplay Questions and Tutorials.

Try entering at a shallower angle, and maybe making more than one entry into the atmosphere.

 

20 hours ago, strigon said:

Yeah, we're going to need a lot more than this.

Some basic tips, however, are to make things as light as possible. You don't need dozens of batteries and the biggest solar panels, for instance. Heat shields are quite heavy, so that might be part of your problem. It also took me a while to seriously consider engine weight; many times, a smaller engine - even if it's less efficient - will get you much further. A simple probe core, with a decent antenna, and a full science package with the half-sized 1.25 metre tank and the "Terrier" engine can make it to Eve from LKO, I believe.

As far as entry, go for a shallow approach. I don't often land at Eve, but 40-50 km is probably the lowest I'd go. If you have to make another pass to actually land, so be it. Aerobraking is notoriously dangerous.

Another tip you might like to use is what's called asparagus staging, or onion staging if you can't make that work.

 

And, just to make sure, how are you transferring to Eve? Are you waiting for a transfer window? Are you leaving Kerbin's orbit and then trying to force an approach? Walk us through what's happening. Because, at a guess, you're either not launching at a transfer window or brute-forcing your approach, wasting a ton of fuel, and resulting in a ridiculously fast approach. So you either run out of fuel, or come flying in so fast your whole craft disintegrates.

 

21 hours ago, Gargamel said:

post a pic of the probe you got, and we can help there too.

Try building a bigger ship for the orbital insertion burn, then release the lander probe separate.  Then you can have a smaller lander, that requires less heat shields. 

 

13 hours ago, blakemw said:

Feathering is consistently effective at Eve, a small scale example which I built for 9000m/s entry at Eve:

It scales up well too. This rather exploits the fact that the game's drag model is too simplistic for hypersonic speeds, even stuff which should be in the wake of the capsule still generates full drag. So basically you can just add lots of these kind of flat pieces (spaced apart) to get as much drag as you like.

The vessel contains 4 small radiators, one large heat shield and one smaller becuz idk why the big one who is supposed to support heat is destroyed always by heat :-/

Finally i landed, but i wanted to land a whole rover, not a simple probe core :-/

[blakemw]

1 minute ago, Luc1fer said:

The vessel contains 4 small radiators, one large heat shield and one smaller becuz idk why the big one who is supposed to support heat is destroyed always by heat :-/

The inflatable heat shield is good only up to about 5500m/s (at Eve) because it lacks ablator. It can be used but you have to be careful to not come in too fast. The heat shields with ablator are good up to about 9000m/s.

[strigon]

Okay, I can't tell a lot about your craft from those pictures, but it looks massively overengineered from what little I can see. You do not, in any way, need eight parachutes to land a probe core on Eve. You don't even need two.

If the rest of your craft is like that, it explains a lot about why you're having trouble. Can you take some pictures from the Vehicle Assembly Building, and share them here? It has much clearer lighting.

[OhioBob]

6 hours ago, Luc1fer said:

The vessel contains 4 small radiators, one large heat shield and one smaller becuz idk why the big one who is supposed to support heat is destroyed always by heat :-/ 

This may be a silly question, but did you inflate the heat shield prior to entry?   Your screenshot shows it in the deflated position.  To work you have to right-click on it and select "Inflate Heat Shield".

Other than that, as long as you don't enter too steeply and too shallow, I see no reason why your vessel shouldn't survive entry.

And I agree that you don't need anywhere near that many parachutes.  Eve air is very dense, so you typically require less parachute than you'd need to land the same probe on Kerbin.

[CrashyMcCrashFace]

Is it even possible to land and re-orbit and get home? I just did an orbit there and refueled on Gilly but just looking at Eve specs I don't see how you'd get large enough craft down and back up again? In any number of hops. Maybe de-orbit and land with almost empty tanks and refuel on the ground before leaving.

[OhioBob]

4 hours ago, CrashyMcCrashFace said:

Is it even possible to land and re-orbit and get home?

It's possible, but it's one of the biggest challenges there is in KSP.  The selection of engines is really important because, at Eve's high atmospheric pressure, there are only a few that can produce adequate thrust.  The Aerospike and Vector are best.  It also takes a lot of delta-v, though I don't remember what the generally accepted value is.  Streamlining is also really important because of the dense air.  One of the biggest hurdles, as I recall, is designing something that can be aerodynamically stable during entry and landing, and then can also be aerodynamically stable during liftoff.

I've landed on and taken off from Eve once, but that was way back in KSP 0.90.  It has changed much since then.  The problem back then was the extremely high drag and designing a vessel with enough delta-v.  I think the delta-v requirement is now much less, but aerodynamic heating and stability are now much bigger issues.

 

Edited May 29, 2018 by OhioBob

[Daniel Prates]

In my book the only parts able to provide a safe entry into Eve are the retractable heat shields. They have a large area when deployed and can be used from the very start of the entry,  so they provide the most deaceleration all the way. Downsize is the complicated design that your craft will require,  but mostly thats all.

[foamyesque]

On 5/29/2018 at 11:39 AM, OhioBob said:

One of the biggest hurdles, as I recall, is designing something that can be aerodynamically stable during entry and landing, and then can also be aerodynamically stable during liftoff

 

The trick there is a winged lander. Works best with ISRU so you don't need to carry absurd amounts of wing coming in, though.

[Spraki]

The others who posted here are far more experienced than I am.

 

One thing I do have to note is not to go overboard with parachutes on Eve. I thought I was gonna come in like a damn rock due to it's gravity... Only to figure out that the air was so dense that my myriads of chutes made the final descent take years ,_, 

This was with a probe along with that being my first time ever at Eve.

I also had the issue of things burning up until I settled for skimming the upper atmosphere several times until I could dive in without becoming soup.

[Xd the great]

Big heat shields, more sas control, aerobrake at 85 km before reentry.

Trust me, eve is hard to land on. Try duna first.

Edited June 4, 2018 by Xd the great