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SRB and Eve


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Due high atmospheric pressure engines are seriously hindered at Eve Surface Level. Most engines become useless with only a  not beaten so badly.  Ignoring how the vessel end up at ESL (assume Hyperedit, Eve Space Program or let's do it anyway) how that goes in regards of solid rocket engines?

A related but secondary question; which liquid fuel engines perform better at ESL(kinda top 3-5)?

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SRBs already have terrible Isp on Kerbin. I don't expect them to be of any use. In fact I'd be surprised if any of them could lift its own weigh.

As for the LF engines good for Eve, the Aerospike, Vector and Mammoth are the top 3. Don't remember much about the other engines since I haven't been there in a very long time.

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Judging by the numbers in the menu, SRBs are not hit in the same way as a terrier. For example, a BACC thumper produces 250kn at Kerbin sea level, 300 kn in space.

It seems also from the numbers in the SPH/VAB that you'll want really vectors or aerospikes - the ISP for vectors at Kerbin sea level are better, but vacuum isp is better for aerospikes. Also vectors have a much higher thrust. This is also consistent with what people have on youtube. Take your pick.

I don't really have experience with eve though...

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I've landed and returned from Eve twice now. Both were 2-Kerbal ships. The first time I used 4 Mainsails for the first stage. I used drilling equipment to refuel, so I was landing an empty ship, which made it a bit easier. The second stage was 4 Darts and 12 Twitches (I didn't know what I was doing). Then the top stage Terrier. It actually got me back to orbit.

The second time was 2 Kerbals, no drilling. I used a single fuselage design. A Mammoth first stage, then a Mainsail, then a Poodle, and finally the Terrier. Worked pretty well.

I've also tried an asparagus-staged Vector design, but the fuel drained frighteningly fast. So I gave that up, but I may try again next time.

As for SRB's; I saw somebody use a Hammer for his second stage. He used a Twin Boar for the first stage. I never would've thought to try that, but he said it actually worked 

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3 Engines for Eve Surface?

-Vector

-Mammoth

-Aerospike

The next best would be the Mainsail, but it's ISP is significantly lower than that of the above. I don't know about the twin boar, might be worth a try.

 

I only use the Vector and Aerospikes for my designs (at least one Vector in the center to provide gimbal is very useful), as I can build nice and sleek asparagus Vehicles with only 1.25 m parts.

 

Forget about every other Engine, especially SRBs.

 

Edit: Check this out if you like. It's an especially easy to use Eve Ascent Vehicle

https://kerbalx.com/Physics_Student/EAV4

Edited by Physics Student
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5 minutes ago, Cpt Kerbalkrunch said:

As for SRB's; I saw somebody use a Hammer for his second stage. He used a Twin Boar for the first stage. I never would've thought to try that, but he said it actually worked 

That is really turning on my curiosity. The twin boar, being a engine with built in fuel tank is another oddball

 

39 minutes ago, Gaarst said:

SRBs already have terrible Isp on Kerbin. I don't expect them to be of any use. In fact I'd be surprised if any of them could lift its own weigh.

Not convince it necessarily holds. At Kerbin SRB's terrible Isp is compensated by high Bang/Buck ratio, being good for a burst of energy right after launch. it may have a similar performance on Eve, not being beaten down as hard as other engines by the high pressure. I don't expect it to have a stellar performance but there is not enough evidence so far to say they are useless.

:prograde:And thank you all for the opinions and experience. Keep it coming.:prograde:

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26 minutes ago, Physics Student said:

I don't know about the twin boar, might be worth a try.

I actually ended up trying the Twin Boar (among many others during Eve testing), but it couldn't get off the ground. I'm prone to larger ships though, so it might've just been a bad design on my part. I'm definitely with you on the SRB's. While I love them on Kerbin, I think they'd be close to useless on Eve. And even if they did well, I don't think it'd be worth hauling them all the way there. And with any radial designs, you definitely have to take drag into account, since it's quite a bit worse on Eve than Kerbin.

And just to clarify, we are talking about sea level on Eve, correct? Above 2kms, things start to get a bit easier. Not much. But easier.

Edited by Cpt Kerbalkrunch
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I know for a fact that at least the Hammer is not able to lift its own weight on Eves surface Level. they do barely if you set the minimum amount of Solid fuel (I actually use them as a separator for the parachutes). Using them higher up will work, of course, but is isn't worth it. a solid stage needs much more mass for the same amount of delta-v, so taking them all the way up as upper stages increases your overall mass significantly. 

the only reasonable situation to use SRBs is on the very first stage to get off Kerbin.

Edited by Physics Student
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6 minutes ago, foamyesque said:

The Mammoth is the way to go. With clever design you can do a sea-level return and only need to discard one engine.

I'm a big believer in the Mammoth myself; especially after my last trip. As far as just ditching one engine though, I think it depends on how many Kerbals you intend to bring. I won't send a single Kerbal on a mission, and I won't use command seats or service module-type gimmickry. So it makes it a bit tougher. For my next Eve mission, I intend to bring the Mk1-2 and see if I can get it back to orbit. Not sure if I'll make it, but you can bet I'll be dumpin' some engines on the way. :)

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2 hours ago, Cpt Kerbalkrunch said:

I'm a big believer in the Mammoth myself; especially after my last trip. As far as just ditching one engine though, I think it depends on how many Kerbals you intend to bring. I won't send a single Kerbal on a mission, and I won't use command seats or service module-type gimmickry. So it makes it a bit tougher. For my next Eve mission, I intend to bring the Mk1-2 and see if I can get it back to orbit. Not sure if I'll make it, but you can bet I'll be dumpin' some engines on the way. :)

I brought back four, in a Mk3 cockpit. First stage was winged drop tanks, to haul me up to proper rocketry altitude without needing TWR > 1, feeding a single mammoth; second stage, the mammoth on a conventional stack of tanks with some wings on for aero stability; third stage, a poodle-powered microshuttle, which met up with a tank left in Eve orbit and acted as the Kerbin lander.

 

Needed a couple more mammoths to get off Kerbin's surface in the first place, but those were winged and recoverable boosters that I landed back at KSC.

Edited by foamyesque
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19 minutes ago, foamyesque said:

I brought back four, in a Mk3 cockpit. First stage was winged drop tanks, to haul me up to proper rocketry altitude without needing TWR > 1, feeding a single mammoth; second stage, the mammoth on a conventional stack of tanks with some wings on for aero stability; third stage, a poodle-powered microshuttle, which met up with a tank left in Eve orbit and acted as the Kerbin lander.

 

Needed a couple more mammoths to get off Kerbin's surface in the first place, but those were winged and recoverable boosters that I landed back at KSC.

Nice. The Mk1-2 is only a little heavier, so that tells me I'll be able to make it. I ditched the radial designs for my second mission cuz my ship kept trying to flip and I felt like the drag I added to straighten out was holding me back. I've since learned to love the Delta Deluxe winglets, so maybe I'll try it again.

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Looking at the atmosphere curves, SRBs are indeed a joke at Eve; their zero-thrust point is just 7 atm compared with the 12 atm of the Vector and Mammoth.

The Vector and Mammoth have identical Isp curves, at 315 sec in vacuum, 295 sec at 1 atm, and 0 at 12 atm. The Aerospike shines relative to this, going from 340 to 290 at 1 atm, 230 at 5 atm (Eve surface level), 170 at 10 atm, and tailing off to 0 at 20 atm.

Engines from the Eve Optimized Engines mod fare better, although they're almost horribly over-specialized for taking off in high-pressure environments.

 

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Agree with all the Vector,  Mammoth,  Dart talk.   If I remember,  the Dart actually has top ISP at sea level,  the Vector is briefly more efficient around 1 atm pressure, and then the Dart gets better again in the thinner air.  Of course,  the Vector destroys the Dart in TWR, and has gimbal.  So a Vector core stage with radial Dart boosters has worked well for me. 

Vacuum engines work fine in a surprisingly large chunk of Eve's upper atmosphere, but I don't recall quite where the cutoff is.  I've generally used the Dart as my second stage to ensure good ISP, but that lack of gimbal can be a hassle.  Poodle or Terrier are also second stage options if your booster has enough delta v to get you relatively high. 

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'Performs better' has multiple dimensions - TWR, ISP, payload fraction  (interplay of multiple factors).  But  there's always this oldie that should still be relevant as engines haven't changed much (at all?) across recent game updates.

http://meithan.net/KSP/engines/

Ignoring staging, basically for very low payloads (under 30 tonnes, not possible to get home?) - aerospike 

Then for some general definition of 'best' to worse, at Eve sea level, Mammoth, Vector, Twin Boar, Mainsail., occasionally switching places depending on ship/payload  + player TWR constraints.

The thing with SRB's is that they come with propellant packed like the Twin Boar. So pack them 25% - 12.5% of the way and the Kickback can be decent for a very short while.  Since we don't care how we got there in the first place :sticktongue:, a 25% packed Kickback can provide 1.45TWR and upwards is it burns (for itself, at 8.4t) for about 12.5s. Some SRB spam in addition to LF engine for the very first bit of the ascent before staging the lot of them could be helpful.

Using the same tool for different  atm pressures should help plan an entire vehicle if we aren't going for an SSTO type launch. Doesn't support SRBs though.

Edited by Weywot8
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I agree with Ultimate Steve and foamyesque. Eve is not about efficiency. All this talk of Isp and TWR is mostly irrelevant. Eve is just about endurance. Which means you plant as much mass as you conveniently can on the ground (which can be quite a lot, since parachutes work so well), and then waste it with complete disregard on the way up.

 

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@Starman4308 @Norcalplanner thanks for the mod suggestion.  Unfortunately for the intent of the question Eve optimised engines don't count.  'Typical'  moded engines (e.g SpaceY) may be considered but the focus is for stock. 

2 hours ago, Weywot8 said:

An interesting tool to play with.  I think it'll keep me busy for awhile   

56 minutes ago, bewing said:

 Eve is not about efficiency. All this talk of Isp and TWR is mostly irrelevant. Eve is just about endurance....

Strongly disagree.  Even your decision, to rebel against this talk of Isp and TWR,  is about efficiency,  just the metric you use to assess it is different. Mind you, a valid metric in its own merit. 

 

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1 hour ago, Spricigo said:

Strongly disagree.  Even your decision, to rebel against this talk of Isp and TWR,  is about efficiency,  just the metric you use to assess it is different. Mind you, a valid metric in its own merit. 

As much as anything on Eve, it is about drag. 

Eve's atmosphere is like mud. So anywhere you can reduce drag will result in significant dV improvement. 

This means less stacks, thinner stacks, less engines, less of anything sticking out, and generally the lowest drag parts. 

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3 hours ago, bewing said:

I agree with Ultimate Steve and foamyesque. Eve is not about efficiency. All this talk of Isp and TWR is mostly irrelevant. Eve is just about endurance. Which means you plant as much mass as you conveniently can on the ground (which can be quite a lot, since parachutes work so well), and then waste it with complete disregard on the way up.

 

 True kerbal style - essentially a version of MOAR BOOSTERS. Disregarding any form of efficiency, everything is about MOAR BOOSTERS. (mostly)

  • launching from Kerbin,  ascent profile - MOAR!
  • get to Duna,  launch window - MOAR!!
  • plane change to polar orbit from equatorial around Jool, raise apoapsis    - MOAR!!!  :cool:

Mostly, because getting off Eve at Sea Level - Rhino: explicitly 0 TWR at 5atm. MOAR of that ain't going to help.

Edited by Weywot8
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9 minutes ago, Spricigo said:

 

3 hours ago, Foxster said:

As much as anything on Eve, it is about drag. 

Bringing fairing to a booster discussion? I'm not sure I understood your point. 

 

It's more about going fast enough and not burning up to minimise drag & gravity loss +++ the cheaper and faster you can head straight up, the thinner the air and the better your performance becomes, what was 2500dV worth of fuel at sea level becomes like ~4000dV for the same amount further up. 

So comparing a flat sardine can shaped ship that's draggy vs a pencil shaped ship of same fuel fractions and engine performance, the pencil shaped ship would win by a huge margin. Essentially @Physics Student approach to Eve.

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