Eve SSTO: any possible ways?

[foamyesque]

14 minutes ago, GoSlash27 said:

Yep. But if you're using additional vehicles to explore then there's no point in making the ascent vehicle SSTO.

Well, for myself, given ISRU, I like to use one vehicle as my to-Eve transfer stage, lander, biome-hopper, and ascent vehicle. All of the first three can readily be accomplished without staging, which only needs to be done during the final return to orbit. It isn't so much "additional vehicles" as it is "multiple-purpose first stage". Part of the reason I'm confident a design along @Kergarin's lines could biome-hop to the mountain is that I have biome-hopped on Eve, and gone above the altitude of the mountain in the process, albiet (as I say) with a multi-stage vehicle but without staging during the hops. A SSTO design will be able to accomplish the same feat, particularly if it can be landed somewhere higher than absolute zero altitude before going for the final jump.

There are pitfalls -- the oceans, or screwing up the landing -- but it can be done. I mean, personally, I'd use a staged vehicle since I'd lay good odds you spend more in fuel to get a SSTO vehicle to Eve (and back!) than being able to recover it would save you, but I don't know why you're so skeptical about this. The larger, ISRU-capable design in the second video is wholly capable of hopping, to my eye.

Edited January 11, 2017 by foamyesque

[GoSlash27]

14 minutes ago, foamyesque said:

I don't know why you're so skeptical about this.

foamyesque,

 Clearly.

15 minutes ago, foamyesque said:

The larger, ISRU-capable design in the second video is wholly capable of hopping, to my eye.

Seems to me that you could just as easily try it as guesstimating by eye. If you think it's so easy to biome- hop, land on a mountain, and then SSTO to orbit then you should have little difficulty doing it.

Best,
-Slashy

[KerikBalm]

On 1/11/2017 at 1:00 AM, Leafbaron said:

what we need for Eve is a scramjet type engine, that generates static charge from the thick atmosphere to power lasers to break the co2 into c and o2, the o2 then can be used to ignite the ethane in the atmosphere. Electric jet propulsion on eve! of course you'd still need chemical rockets to achieve the speeds to get the scramjet fired up. 

This is basically a perpetual motion machine.... unless you're assuming that Eve weather already has static charge built up... and it would basically be like saying you'll make a lightning powered aircraft on Earth.

 

22 hours ago, Marzl said:

Basically that exactly is what I did in my mod. I use an intake and lot of electricity to split co2 to o2, with that you are able to use all jet engines on eve (and duna) then.

I was not able to do a release due to missing time, but may be next week I will be able to. But it is already working as designed

IMO, this is ridiculous. CO2 has no usable energy (excluding nuclear reactions, or reactions with fluorine). All that electric energy you spend to split it is going to be greater than what you get when you combust the split products. Where does the electric charge come from? solar? just use an electric fan. Nuclear? just go with a nuclear thermal turbojet. Chemical/Fuel cells? just directly combust the fuel, you gain nothing by combusting it to make energy to split other compounds to combust the products.

This is what we need:

 

 

 

 

 

 

 

[foamyesque]

10 hours ago, GoSlash27 said:

foamyesque,

 Clearly.

Seems to me that you could just as easily try it as guesstimating by eye. If you think it's so easy to biome- hop, land on a mountain, and then SSTO to orbit then you should have little difficulty doing it.

Best,
-Slashy

The hard bit's the SSTO piece.

[Blaarkies]

11 hours ago, foamyesque said:

Well, for myself, given ISRU, I like to use one vehicle as my to-Eve transfer stage, lander, biome-hopper, and ascent vehicle. All of the first three can readily be accomplished without staging, which only needs to be done during the final return to orbit. It isn't so much "additional vehicles" as it is "multiple-purpose first stage". Part of the reason I'm confident a design along @Kergarin's lines could biome-hop to the mountain is that I have biome-hopped on Eve, and gone above the altitude of the mountain in the process, albiet (as I say) with a multi-stage vehicle but without staging during the hops. A SSTO design will be able to accomplish the same feat, particularly if it can be landed somewhere higher than absolute zero altitude before going for the final jump.

There are pitfalls -- the oceans, or screwing up the landing -- but it can be done. I mean, personally, I'd use a staged vehicle since I'd lay good odds you spend more in fuel to get a SSTO vehicle to Eve (and back!) than being able to recover it would save you, but I don't know why you're so skeptical about this. The larger, ISRU-capable design in the second video is wholly capable of hopping, to my eye.

This! This is amazing, i have always just been content with the lander staying upright and being on land (i mean, its in the name). But i had an ISRU and could probably jump 10km at a time using only the bottom tank...good enough to find higher ground for sure, except repacking the parachutes is a small problem.

No longer do we need to design Eve landers to be sea-level capable, thanks!

[tseitsei89]

Does anyone know the coordinates of the highest mountain? This biome hop + SSTO thing sounds like something I might want to attempt at some point but coordinates of the best launch side would be very useful...

[GoSlash27]

3 hours ago, foamyesque said:

The hard bit's the SSTO piece.

foamyesque,

 Good to see you coming around to the notion that there are "hard pieces" But the SSTO piece has been done. I think the tricky bit will be doing these different jobs with a single design. Operating at or near sea level is a lot easier with a higher t/w, but an SSTO can't haul all those engines. An SSTO is going to necessarily be tall and spindly with nothing to help stabilize it. Not an easy design to land on uneven terrain with tight fuel. And so on...

Best,
-Slashy

[foamyesque]

8 hours ago, GoSlash27 said:

foamyesque,

 Good to see you coming around to the notion that there are "hard pieces" But the SSTO piece has been done. I think the tricky bit will be doing these different jobs with a single design. Operating at or near sea level is a lot easier with a higher t/w, but an SSTO can't haul all those engines. An SSTO is going to necessarily be tall and spindly with nothing to help stabilize it. Not an easy design to land on uneven terrain with tight fuel. And so on...

Best,
-Slashy

 

Man, I've never said SSTOing from Eve is either easy or practical. This whole chain came about because I pointed out that one particular part of it -- a restricted set of launch areas -- doesn't mean you have to land in those launch areas. As for tall-and-spindly, that's true to some extent but it's actually less true on Eve than nearly anywhere else because of the huge multipliers from keeping your TWR up. If you look at the examples provided you can see they have pretty substantial footprints.

[Reusables]

On 2017. 1. 11. at 6:35 PM, KerikBalm said:

Those stock electric props, as far as I know, rely on splitting the craft into two parts and using reaction wheel craft to turn the prop, which will push/pull the associated craft along a "stock bearing" while physics simulations are going on. I'm pretty sure that they fall apart once placed on rails - so not usable. in this context

Propeller rotors can be re-docked to the stator by shielded docking port/claw reliably. So it is reusable if only it can get into the orbit.

On 2017. 1. 11. at 8:14 PM, cantab said:

I doubt "stock propellers" are going to be workable because of the mass and drag penalty they'll cause. It'll be fine when you're just pootling up on the propeller, but once you light the rockets that drag is going to bite. Maybe if you can squeeze a working prop into a cargo or service bay you might have something, but that's a tall order too and doesn't address the mass.

Yeah, the mass penalty is very big. I made propellers of TWR 4(half of jets), but still it is marginal for SSTO. (I'd go up to stratosphere)

About the drag penalty, I think it won't be too much as it'll be certainly smaller than wing surfaces, and fully deploying it will make it parallel to the airflow. (4 Big-S control surfaces is simillar size with a structural wing C)

By the way, isn't a plane with TWR 0.5 supposed to be fly well even in stratosphere? How much winget surface  per ton do I need for this?

[Sharpy]

1 hour ago, Abastro said:

Propeller rotors can be re-docked to the stator by shielded docking port/claw reliably. So it is reusable if only it can get into the orbit.

By the way, isn't a plane with TWR 0.5 supposed to be fly well even in stratosphere? How much winget surface  per ton do I need for this?

The stock propellers have a nasty habit of exploding horribly at speeds exceeding 150m/s. Unless you manage to re-dock them mid-flight before switching to rockets, you're in for a boom.

TWR of 0.5 can keep you airborne at any altitude that gives you reasonable lift. The problem is the thinner the atmosphere the weaker the lift - and it's lift that gives propellers thrust; TWR 0.5 at Kerbin sea level will be zilch at 10km.

 

[Reusables]

8 hours ago, Sharpy said:

The stock propellers have a nasty habit of exploding horribly at speeds exceeding 150m/s. Unless you manage to re-dock them mid-flight before switching to rockets, you're in for a boom.

Yeah, it likes to explode on high speed/altitude though the limit can vary via control surface pitch.

So, I'm planning to re-dock it in flight. It's really problem of typing speed, and it will get easier if I change the design.

8 hours ago, Sharpy said:

TWR of 0.5 can keep you airborne at any altitude that gives you reasonable lift. The problem is the thinner the atmosphere the weaker the lift - and it's lift that gives propellers thrust; TWR 0.5 at Kerbin sea level will be zilch at 10km.

I forgot about that since my 40t plane flied better on 10km. I thought drag decreases faster than lift till specific altitude around 9km...

As it isn't the case, I might go bigger and lower.

How's the lift&drag characteristics for altitude and speed? Anyone knows? This could be really helpful..

[Sharpy]

5 hours ago, Abastro said:

How's the lift&drag characteristics for altitude and speed? Anyone knows? This could be really helpful..

Both quadratic with speed, linear with pressure, which is inverse exponential with altitude  Drag and lift depend on these in exactly the same way, differing only by a constant factor, dependent on plane geometry (angle of attack, wing surface, plane crossection etc).

Would seem very fun allowing for engines not depending on intake air to allow SSTO through arbitrarily slow climb and acceleration, if not one more factor: ram rise. It's the air temperature 'as felt by the airplane skin', the reason why you're covered in flames. It's dependent on speed squared in Mach, times ambient air temperature in Kelvins. That plays a really nasty trick, as up to about Mach 1.5 it's very mild and manageable and above starts climbing at a really alarming rate, reaching quite solar core temperatures at mach 21 (Earth LEO speed). Luckily Kerbin's LEO speed is much lower, but it's still a good reason why aerocapture is a risky business.

[Reusables]

1 hour ago, Sharpy said:

Both quadratic with speed, linear with pressure, which is inverse exponential with altitude  Drag and lift depend on these in exactly the same way, differing only by a constant factor, dependent on plane geometry (angle of attack, wing surface, plane crossection etc). 

Doesn't that mean level flight is always possible on most altitude with constant thrust(certain TWR)? In other words, lift-drag ratio is constant for certain AoA. Do you mean that?

[Sharpy]

35 minutes ago, Abastro said:

Doesn't that mean level flight is always possible on most altitude with constant thrust(certain TWR)? In other words, lift-drag ratio is constant for certain AoA. Do you mean that?

1) thrust in all airbreathers and props is related to pressure; you're losing TWR with pressure. Only rocket is immune to that (and benefits from pressure drop) - but then, it needs to carry own oxidizer and run near stochiometric rate. Jets push tons upon tons of air through while burning relatively little kerosene.

2) ram rise.

But if you can somehow deal with these two... there's just one obstacle left: pressure drop with altitude is exponential, lift rise with speed is quadratic, so you must gain speed at a higher rate than you gain altitude... and long before you're out of the atmosphere you reach orbital speed. Your gravitational drag drops so much lift becomes entirely moot and only atmospheric drag matters. Accelerating farther won't let you stay in horizontal (parallel to the surface) flight as your trajectory throws you out of the atmosphere, and lift (negative, at negative AOA) from certain altitudes won't be able to prevent that.

Essentially that's what "arduous climb" profile SSTOs do in KSP - e.g. based only on Whiplash and LV-N, no oxidizer. They circularize around 40km and only then rise apoapsis above the atmosphere.

Edited January 14, 2017 by Sharpy

[Reusables]

22 minutes ago, Sharpy said:

1) thrust in all airbreathers and props is related to pressure; you're losing TWR with pressure. Only rocket is immune to that (and benefits from pressure drop) - but then, it needs to carry own oxidizer and run near stochiometric rate. Jets push tons upon tons of air through while burning relatively little kerosene.

2) ram rise.

But if you can somehow deal with these two... there's just one obstacle left: pressure drop with altitude is exponential, lift rise with speed is quadratic, so you must gain speed at a higher rate than you gain altitude... and long before you're out of the atmosphere you reach orbital speed.

Essentially that's what "arduous climb" profile SSTOs do in KSP - e.g. based only on Whiplash and LV-N, no oxidizer. They circularize around 40km and only then rise apoapsis above the atmosphere.

Then I think I can just add more wing surfaces to improve L/D and max altitude. Thanks!

On the other hand, I found that I need to try the props on eve surface as they gets more drag slowing the rotation. It seems that thrust decreases over certain pressure... In the case, this will be the certain limit. 

[Sharpy]

18 minutes ago, Abastro said:

Then I think I can just add more wing surfaces to improve L/D and max altitude. Thanks!

On the other hand, I found that I need to try the props on eve surface as they gets more drag slowing the rotation. It seems that thrust decreases over certain pressure... In the case, this will be the certain limit. 

Yep - thrust decreases with pressure drop and that IS your fundamental limit on altitude on props. You'd be able to do everything you wish with sustained TWR, but that is something not achievable on engines that depend on pushing air. More wing surface increases drag and mass, further reducing your TWR, and it's the TWR and not lift that is your ultimate limiting factor.

Edited January 14, 2017 by Sharpy

[Reusables]

37 minutes ago, Sharpy said:

Yep - thrust decreases with pressure drop and that IS your fundamental limit on altitude on props. You'd be able to do everything you wish with sustained TWR, but that is something not achievable on engines that depend on pushing air. More wing surface increases drag and mass, further reducing your TWR, and it's the TWR and not lift that is your ultimate limiting factor.

Yeah, but what I mean was that thrust of props is affected by drag. Since L/D ratio is only dependent on AoA, thrust is proportional to drag assuming constant AoA. I expect the drag to be nearly same as torque from SAS modules divided by radius, as other friction will be small. This means that thrust will be constant for certain AoA and nominal friction.

[Sharpy]

4 hours ago, Abastro said:

Yeah, but what I mean was that thrust of props is affected by drag. Since L/D ratio is only dependent on AoA, thrust is proportional to drag assuming constant AoA.

That's an unrealistically idealistic assumption.

So, your propeller suffers less drag, so the same torque can make it spin faster, until the drag is the same as it was, and resulting thrust/lift (in case of propeller blade these are equivalent) gets back to prior level.

Your problem is in "spin faster".

In real life minuscule instabilities resulting from fabrication imperfections grow to forces that bend, stretch and dislocate the engine elements, and the engine explodes. In KSP minuscule instabilities resulting from floating point calculations grow into displacements that crash the rotor into the chassis and the engine explodes. With falling drag, constant torque, RPM grows, and stock bearings simply can't handle that.

[Reusables]

19 minutes ago, Sharpy said:

That's an unrealistically idealistic assumption.

So, your propeller suffers less drag, so the same torque can make it spin faster, until the drag is the same as it was, and resulting thrust/lift (in case of propeller blade these are equivalent) gets back to prior level.

Your problem is in "spin faster".

In real life minuscule instabilities resulting from fabrication imperfections grow to forces that bend, stretch and dislocate the engine elements, and the engine explodes. In KSP minuscule instabilities resulting from floating point calculations grow into displacements that crash the rotor into the chassis and the engine explodes. With falling drag, constant torque, RPM grows, and stock bearings simply can't handle that.

I know that it won't work that way for smaller drag on higher atmosphere(maybe a bit over sea level). What I wanted to say was that there would be maximum thrust the propellers can provide on high density(drag). Thus higher atmospheric pressure would make the effects other than drag nominal.

That's why I said that I should test the plane on eve sea level.

[Sharpy]

28 minutes ago, Abastro said:

I know that it won't work that way for smaller drag on higher atmosphere(maybe a bit over sea level). What I wanted to say was that there would be maximum thrust the propellers can provide on high density(drag). Thus higher atmospheric pressure would make the effects other than drag nominal.

That's why I said that I should test the plane on eve sea level.

Sea level prop plane for Eve is a very reasonable solution (other than their natural tendency to explode, and no convenient 'recover' button in order to deploy a replacement). Just don't expect it to go anywhere very high or be a reasonable SSTO phase.

[Reusables]

11 minutes ago, Sharpy said:

Sea level prop plane for Eve is a very reasonable solution (other than their natural tendency to explode, and no convenient 'recover' button in order to deploy a replacement). Just don't expect it to go anywhere very high or be a reasonable SSTO phase.

Do you mean somewhere over 12km by high? I don't expect that propellers ever work there either. I wanted to see if rocket engines can get rest of the plane to the orbit, though it will certainly be marginal to impossible for eve.

[Sharpy]

45 minutes ago, Abastro said:

Do you mean somewhere over 12km by high? I don't expect that propellers ever work there either. I wanted to see if rocket engines can get rest of the plane to the orbit, though it will certainly be marginal to impossible for eve.

 To reach orbit from Eve, even 12km, you need a big, heavy rocket. To lift such a rocket you need a mighty propeller. And to lift that propeller to orbit from Eve...?

I suggest you try Kerbin first. SSTO that goes, say, 5-8km up on propeller, more if you can manage it, the rest on rockets. If it works on Kerbin, it might work on Eve, but if it doesn't work on Kerbin, you can be sure as hell it won't work on Eve.

Edited January 14, 2017 by Sharpy

[Reusables]

12 minutes ago, Sharpy said:

 To reach orbit from Eve, even 12km, you need a big, heavy rocket. To lift such a rocket you need a mighty propeller. And to lift that propeller to orbit from Eve...?

I suggest you try Kerbin first. SSTO that goes, say, 5-8km up on propeller, more if you can manage it, the rest on rockets. If it works on Kerbin, it might work on Eve, but if it doesn't work on Kerbin, you can be sure as hell it won't work on Eve.

So I've been trying it on Kerbin, which seems to work better. I was lacking wings and had too much nukes, I'm adjusting those now.

(My calculation shows that aerospike-only configuration will yield 3k dv and reasonable thrust for entire flight which would be enough for Kerbin, but on Eve it just lacks dv)

[Sharpy]

11 minutes ago, Abastro said:

So I've been trying it on Kerbin, which seems to work better. I was lacking wings and had too much nukes, I'm adjusting those now.

(My calculation shows that aerospike-only configuration will yield 3k dv and reasonable thrust for entire flight which would be enough for Kerbin, but on Eve it just lacks dv)

Yup. You'll be able to start the burn from about the same pressure, so same efficiency - but you need more delta-V to get to the orbit. Arrive into LKO with some 1.5km/s to spare and you should be fine on Eve.

[Reusables]

I found that I'm getting more drag on higher altitude during level flight. (Using the aero gui)

It's probably because of the AoA increase to compensate the reduced lift, but how does the airplane compensate the drag in this case? The only cause I can think of is increase in thrust..