SRB and Eve

[Cpt Kerbalkrunch]

9 hours ago, Ultimate Steve said:

Funny you mention that, as I'm in the process of designing an SRB only Eve Ascent Vehicle. I found that the ISP's are decent enough provided you're on a tall mountain.

That sounds interesting. Is it SRB only 'til it's out of the atmosphere, or all the way to orbit?

[Human Person]

13 minutes ago, Cpt Kerbalkrunch said:

That sounds interesting. Is it SRB only 'til it's out of the atmosphere, or all the way to orbit?

Tere's a huge difference between Eves sea level and eves highest mountains. You have good chances on the mountains.

[Spricigo]

43 minutes ago, Weywot8 said:

sardine can VS   pencil 

The advantages of better heat resistance and less drag are clear.  It's the relationship with what he quoted that eludes me. 

[Cpt Kerbalkrunch]

45 minutes ago, Physics Student said:

Tere's a huge difference between Eves sea level and eves highest mountains. You have good chances on the mountains.

Agreed. It just got me to thinking that it sounded like a good challenge: SRB's only from the surface of Eve to orbit. Might be a bit tedious, but fun as well. You'd have to cheat your ship to Eve and land it each time just to test it. Definitely sounds interesting, though.

Edited June 29, 2017 by Cpt Kerbalkrunch

[Gordon Fecyk]

8 minutes ago, Cpt Kerbalkrunch said:

You'd have to cheat your ship to Eve and land it each time just to test it. Definitely sounds interesting, though.

Well... I did just finish updating this add-on that would be perfect for such tests, if you didn't mind keeping a second KSP installation around. A trailer video is in the spoiler.

Spoiler

 

 

[Foxster]

1 hour ago, Spricigo said:

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

 

There's no particular need for a faring, though it can help with the whole streamlining process with some Eve craft. 

My point is that as well as the discussion about isp and TWR, a really very important factor is drag. Throwing a lot of inefficient SRBs on a craft, along with their decouplers, will add drag and that will reduce their efficiency even further. 

Edited June 29, 2017 by Foxster

[Spricigo]

33 minutes ago, Foxster said:

My point is that as well as the discussion about isp and TWR, a really very important factor is drag. Throwing a lot of inefficient SRBs on a craft, along with their decouplers, will add drag and that will reduce their efficiency even further. 

But drag is a concern regardless of engine Isp and  TWR. If anything SRBs lack the ability to throttle down. 

[Human Person]

1 hour ago, Cpt Kerbalkrunch said:

Agreed. It just got me to thinking that it sounded like a good challenge: SRB's only from the surface of Eve to orbit. Might be a bit tedious, but fun as well. You'd have to cheat your ship to Eve and land it each time just to test it. Definitely sounds interesting, though.

It has been done before

 

[Cpt Kerbalkrunch]

1 hour ago, Gordon Fecyk said:

Well... I did just finish updating this add-on that would be perfect for such tests, if you didn't mind keeping a second KSP installation around. A trailer video is in the spoiler.

  Hide contents

 

 

I play straight-vanilla, but that was a great video. I keep saying when I get bored of the stock game (which still hasn't happened) I'll add a planet pack and some other mods to spice things up. I think this might make the list. Very cool.

 

17 minutes ago, Physics Student said:

It has been done before

 

Pretty much sums up life, doesn't it? 

[Ultimate Steve]

4 hours ago, Cpt Kerbalkrunch said:

That sounds interesting. Is it SRB only 'til it's out of the atmosphere, or all the way to orbit?

Not to derail the thread too much, but it's actually an almost entirely SRB powered grand tour that I'm trying to do. The "almost" meaning I can use RCS to dock if I want.

[Spricigo]

Just now, Ultimate Steve said:

Not to derail the thread too much, but it's actually an almost entirely SRB powered grand tour that I'm trying to do. The "almost" meaning I can use RCS to dock if I want.

The thread's subject is basically Speculation About Unorthodox Use Of Solid Rocket Engines, I think you  project is, at least, interestingly close related ...As would be using SRB for docking maneuver (That! Would Be a Challenge!)

[Cpt Kerbalkrunch]

18 minutes ago, Ultimate Steve said:

Not to derail the thread too much, but it's actually an almost entirely SRB powered grand tour that I'm trying to do. The "almost" meaning I can use RCS to dock if I want.

Wow. Love the ambition, but I'm picturing about a hundred hours of testing. 

 

And what would you be docking for, more monopropellent? 

[Ultimate Steve]

Just now, Cpt Kerbalkrunch said:

Wow. Love the ambition, but I'm picturing about a hundred hours of testing. 

 

And what would you be docking for, more monopropellent? 

Docking would be for the "refueling" of the mothership, AKA adding more stacks of solid rocket boosters along the way because my computer can't handle the whole ship at one time.

As for the hundred hours of testing, I have spent eight so far on the Eve lander alone.

Speaking of the Eve lander, I can enter Eve's atmosphere, glide to and pinpoint land at the tallest peak, take off, and enter orbit. However, I'm having a bit of trouble getting rid of one of the pesky forward heat shields...

[bewing]

Have you tried the "Normal hold" trick?

 

[wumpus]

15 hours ago, Abastro said:

I'm quite sure that SRBs will only worth it for the money. They are pretty cheap to dispose of, but have no good Isp. (which is especially critical on Eve)

The only way SRBs will be "worth it for the money" is if they are lifted to LKO by spaceplane and taken from LKO to Eve via LV-Ns.  And even then it  will be hard to justify.  The problem of bad Isp is compounded every time you supply it with delta-v.

I like SRBs.  I'm even aware of times they make sense to use as second stages (rare, but similar to the times it makes sense to reduce their thrust).  But don't expect to be able to justify them much past the surface of Kerbin.

[Spricigo]

Just now, wumpus said:

The only way SRBs will be "worth it for the money" is if they are lifted to LKO by spaceplane and taken from LKO to Eve via LV-Ns.  And even then it  will be hard to justify. 

As I said in my original post: Ignoring how the vessel end up at ESL (assume Hyperedit, Eve Space Program or let's do it anyway)

Recoverable ultra efficient transport is not even the cheapest option available. They may worth the money because its an Eve Space Program.

OTOH using Extra-Planetary Launchpads to build it they may not worth the money because nothing have a value in funds, the difference between build SRBs or something else is how much time warp is necessary.

For the proposal of this discussion it don't need to be efficient, feasible is enough.

 

 

 

[Reusables]

Well, I should've elaborated this: SRBs are not useful if the goal is not about money. (i.e. I meant 'if only' with the word 'only')

No need to use it for either simplicity, aesthetics or mass.

On the other hand, now I realized there is one more case for SRBs: when you challenged yourself to create eve ascent vehicle out of SRBs.

[magnemoe]

On 28.6.2017 at 11:36 PM, 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. 

The mammoth is a bit of an overkill as I see it unless multiple crews, think the lightest ship you get is aerospike in asparagus, second is vector who let you use an capsule.

[Foxster]

1 hour ago, magnemoe said:

The mammoth is a bit of an overkill as I see it unless multiple crews, think the lightest ship you get is aerospike in asparagus, second is vector who let you use an capsule.

The lightest single-manned craft that you can get from Eve sea level to orbit uses a single vector and then a terrier. 

[Cpt Kerbalkrunch]

4 hours ago, magnemoe said:

The mammoth is a bit of an overkill as I see it unless multiple crews, think the lightest ship you get is aerospike in asparagus, second is vector who let you use an capsule.

A multi-Kerbal ascent is exactly what I used it for. I wanted to keep drag to a minimum, so no radial parts. That meant a single-fuselage design (the pencil shape or, in this case, magic marker). I don't know if another single engine could lift that kind of mass off of Eve at sea level.

[magnemoe]

10 hours ago, Foxster said:

The lightest single-manned craft that you can get from Eve sea level to orbit uses a single vector and then a terrier. 

Any workable designs? the dV map don't work out for me, 

[Foxster]

3 hours ago, magnemoe said:

Any workable designs? the dV map don't work out for me, 

The capsule is a tad creative to reduce the launch mass to an absolute minimum, about 18.5t. It has a short pointy fairing clipped inside the lander can to make it have zero drag, at the expense of the mass and drag of the fairing. 

The same can be achieved with a more conventionally used fairing but that pushes the mass up slightly, Like this...

Edited July 1, 2017 by Foxster

[magnemoe]

Why the side boosters with 48-7s? that thing will have an insane twr without them. 
Would you not get serious drag an heating issues with the landing can with no nose cone. The 0.625 cone on top of an MK1 pod tend to explode during accent  

[Foxster]

59 minutes ago, magnemoe said:

Why the side boosters with 48-7s? that thing will have an insane twr without them. 
Would you not get serious drag an heating issues with the landing can with no nose cone. The 0.625 cone on top of an MK1 pod tend to explode during accent  

In the 2nd craft, those aren't Sparks, they are the little air intakes. They are just a low-drag flat end for the drop tanks to help with landing the craft. 

In the 1st craft, as I explained above, the lander can is actually "inside" a fairing, it just happens to be quite small and clipped inside the lander can in a slightly "cheaty" way to reduce the drag of the lander can to zero.

Pro tip 1: Fairings can be pre-built and then re-positioned so they clip inside other parts and as long as they protrude just a bit from them then they still do their job.

Pro tip 2: In the 2nd craft you can see the bottom of the drop tanks offset in steps. This was just there to help with the landing. This does not add to the drag of the drop tanks, strangely.  This is because drag is calculated in KSP based on where a part is first placed, if you move it afterwards with the translate tool then the drag does not change (as long as you don't rotate the part too). 

0.625 cone exploding: You will get that depending on your flight profile. You want to be punching up quickly to start with, with as much time as possible close to a zero AoA , using throttle control to maintain a prograde direction. If you go full-throttle all the way to orbit then, yes, things may get a tad warm-ish. 

Edited July 1, 2017 by Foxster

[magnemoe]

42 minutes ago, Foxster said:

In the 2nd craft, those aren't Sparks, they are the little air intakes. They are just a low-drag flat end for the drop tanks to help with landing the craft. 

In the 1st craft, as I explained above, the lander can is actually "inside" a fairing, it just happens to be quite small and clipped inside the lander can in a slightly "cheaty" way to reduce the drag of the lander can to zero.

Pro tip 1: Fairings can be pre-built and then re-positioned so they clip inside other parts and as long as they protrude just a bit from them then they still do their job.

Pro tip 2: In the 2nd craft you can see the bottom of the drop tanks offset in steps. This was just there to help with the landing. This does not add to the drag of the drop tanks, strangely.  This is because drag is calculated in KSP based on where a part is first placed, if you move it afterwards with the translate tool then the drag does not change (as long as you don't rotate the part too). 

0.625 cone exploding: You will get that depending on your flight profile. You want to be punching up quickly to start with, with as much time as possible close to a zero AoA , using throttle control to maintain a prograde direction. If you go full-throttle all the way to orbit then, yes, things may get a tad warm-ish. 

Did not know the fairing tricks, 
And I lowed the landing legs with fuel.