Tips on building Mk3 SSTOs?

[Firemetal]

Hi. You guys must know me as the idiot who doesn't understand re-entry very well. Anyway I have a different question today.

Do any of you master SSTO builders have any tips on building interplanetary (Not cargo sstos to get into orbit) SSTOs? I have built two that can get into orbit. They both have an easy ascent path due to a super overpowered TWR. They are very different. One of them is basically a rip-off of Omnichrome's Duna cargo ssto.

https://www.youtube.com/watch?v=arujaPn4EBY

The other one has instead of a big cargo bay, a big mk3 fuselage. I believe (haven't yet tested it) that it can get to Laythe and back, having around 1000 units of oxidizer left in LKO. Here is a 3 picture album that shows the two SSTO's either in action or in the SPH.

 

Ok so I suck at building SSTOs. May I have some tips on building a good SSTO or if I'm doing anything wrong in these SSTOs or just complement me on my halfway decent SSTO designs??? Eh just give me the protips.

[bewing]

The last thing you want to do is spam engines. Engines are heavy. You want the minimum number of engines that will get you and all your fuel and payload (if any) to orbit. Once you've gotten to orbit, all you need is one. If Dusk2 has 4 engines, that's better than 8. It still may be too many, but it's better at least.

But MK3's are quite heavy things, and 1000 units of oxidizer probably won't even get you to the Mun.

So, are you actually planning on dragging cargo with you in the SSTO on your interplanetary journey?

[Geschosskopf]

12 hours ago, Firemetal said:

Eh just give me the protips.

I'm no SSTO expert but I know the general rules ....

First off, when planning interplanetary trips, don't think in terms of units (liters) of fuel / oxidizer, think in terms of dV.  It's dV that gets you places, and the number of units of fuel / oxidizer needed to create a given amount of dV varies with the mass of the ship and the type of engines it has.  Trips to the various planets require different amounts of dV as shown on the dV maps, so to get to a given planet, your SSTO needs rocket fuel tankage that will hold however much dV that trip needs.  However, not all the rocket fuel tanks don't have to be launched full.

Most SSTOs burn nearly all their fuel just getting to LKO.  Thus, most designs can't get to another planet without refueling soon after launch.  And they usually can't carry enough rocket fuel for a round trip, either.  So, the most common design for an interplanetary SSTO has a built-in drill and ISRU to refuel itself, and it needs to reach LKO with about 1500m/s of rocket fuel left in its tanks.  This fuel lets it get to Minmus, land there, and refuel, including filling any extra rocket fuel tanks that were launched empty, but which it needs for the long interplanetary trip.  Then it can go to the target planet, where it will usually have to refuel itself again for the trip home.  See, any fuel intended for use on the interplanetary trip counts as payload for the initial lifter, because the lifter can't use it itself.  For an interplanetary trip further than Duna, this becomes a very heavy load, so it's best not to have to lift it with an SSTO.

I personally am not a fan of interplanetary SSTOs, except maybe for Duna, and then mostly just for style points, not practicality.  The main reason is because whereas a conventional rocket stages away its initial lifter during launch, when it no longer needs it, an SSTO is stuck lugging it around (in the form of wings, jet engines, intakes, and jet fuel tanks) forever.  Thus, while SSTOs might be more efficient at getting stuff to LKO, they're way less efficient at moving stuff around in space because they're burdened with all this dead airframe weight.  This mass serves no useful purpose anywhere except Kerbin and Laythe.  In between those places, and at every other planet, all it does is wreck fuel efficiency and payload fraction.  If you've got enough tanks for the trip and plan on refueling for free along the way, then maybe you don't care about fuel efficiency in space.  However, the payload fraction problem never goes away.  But hey, style points.

[Firemetal]

I mean like Matt Lowne's Argus. Oh and I tried on the panther jet engines on my latest design in wet mode. They seemed to be doing quite well since at that point they had the same thrust as the whiplash engines but they burn fuel a lot quicker. They do give extra control but is it really worth it?

[Firemetal]

7 hours ago, bewing said:

The last thing you want to do is spam engines. Engines are heavy. You want the minimum number of engines that will get you and all your fuel and payload (if any) to orbit. Once you've gotten to orbit, all you need is one. If Dusk2 has 4 engines, that's better than 8. It still may be too many, but it's better at least.

But MK3's are quite heavy things, and 1000 units of oxidizer probably won't even get you to the Mun.

So, are you actually planning on dragging cargo with you in the SSTO on your interplanetary journey?

Dusk 2 replaced the cargo with a fuel tank.

Also you don't watch Matt Lowne, do you? Then you wouldn't know that 4 engines is probably the best. You see I'm planning on taking one of these to Duna. You need at least a .5 TWR (correct me if I'm wrong :/) to take off from Duna. 1 engine would be below .1 TWR! When I say 1000 units of oxidizer is left, I mean if I ever took it to Laythe, it could switch modes while still in the atmosphere and move the ap over 50km. Alright? I could of used less rapiers. I know.

But thanks anyway.

[Firemetal]

Heh forget the protips.

Dusk 2 is the one. Just a quick question though. I tried landing like a normal plane on Duna but it kept smashing into the ground even with the parachutes. I believe it is a lack of drag but I just want to confirm that. If I move this pair of wings down and add another pair of wings above it (like the Argus) will it land properly? I had to land it like a rocket due to this fail.

[bewing]

The parachute part of it is lack of drag. Did you land in the equatorial canyon like you are supposed to?

But the non-horizontal landing part is lack of lift -- especially at the front end. Adding more wing will not help.

Landing horizontally is all amusing and everything, but landing like a rocket on your engine bells, and then tipping yourself forward onto your wheels is much more efficient on lowish-gravity worlds. The only way you can manage to do horizontal landings is to put some vernors under your nose and burn them continuously to keep you level.

[Firemetal]

No I landed in a small crater slope. I have a lot of oxidizer left so I guess I'll use the parachutes at the front to slow me down more so I can minimize the usage of Oxidizer.

Thanks! 

Edit:

Quote

The only way you can manage to do horizontal landings is to put some vernors under your nose and burn them continuously to keep you level.

Uh you mean like A VTOL? I guess I could make a VTOL SSTO after this. But again thanks for your help!

Edited July 5, 2016 by Firemetal

[bewing]

The air is significantly thicker in the canyon -- flying and parachuting is quite a bit easier down there.

 

 

Edited July 5, 2016 by bewing

[Firemetal]

But harder to take off. I wasted most of my fuel fighting the thickest part of the atmosphere anyways and couldn't make it back but it was "an experiment". Or just simply trial and error. 

Thanks!

[Firemetal]

On July 5, 2016 at 8:33 AM, Firemetal said:

I mean like Matt Lowne's Argus. Oh and I tried on the panther jet engines on my latest design in wet mode. They seemed to be doing quite well since at that point they had the same thrust as the whiplash engines but they burn fuel a lot quicker. They do give extra control but is it really worth it?

Omg the SSTO God liked my post. Thanks Matt!

[Matt Lowne]

On 06/07/2016 at 2:26 AM, Firemetal said:

But harder to take off. I wasted most of my fuel fighting the thickest part of the atmosphere anyways and couldn't make it back but it was "an experiment". Or just simply trial and error. 

Thanks!

The Argus uses 6 parachutes to land on Duna and it has 2 airbrakes as well! 

 

You don't need additional engines on the nose to do a horizontal landing, just keep trying over and over. Make sure you use the right landing gear too, the Argus, Engadine and Argus II all use the small gear, which is pretty useless in 1.1. The Odyssey fixes this issue (see my forum post for more info if you're interested).

The Argus 2 was designed to land on Laythe (much more forgiving than Duna for landings) and that still needed 3 parachutes!

Note that both crafts (especially Argus 2) have huge front canards, see below for a good shot of this.

Other than that, it's like you say. Lots and lots (and lots and lots and lots) of trial and error. Mostly error. My "Argus Class" consists of 5 ships: Argus, Argus 2, Odyssey and Engadine (there's also Engadine 2, but Odyssey renders it obsolete so it has never been filmed). What you don't see are the ones that didn't make the cut. Ambition 1, Ambition 2, Resurgence, Resurgence v2, Uprising, Undulator, Raven, Raven 2, Raven 3, Oscillator, Scythe are all craft files that never made it. Below is the Raven 2, probably the "best of the worst" when it comes to failed prototypes. Eventually it was beaten out by the Cutlass H, which would then be renamed to Argus 2.

[Firemetal]

Thanks Matt! I will not give up on my SSTO building but taking a short breather while I explore Pol and Bop.

A little question though. Where is a good place to start with Duna SSTOs? Mk1, 2 or 2?

(oh aren't I lucky)

[Matt Lowne]

11 minutes ago, Firemetal said:

Thanks Matt! I will not give up on my SSTO building but taking a short breather while I explore Pol and Bop.

A little question though. Where is a good place to start with Duna SSTOs? Mk1, 2 or 2?

(oh aren't I lucky)

Mk2 is the most forgiving. 

With SSTOs, the best learning steps are:

1. Minmus

2. Mun/Gilly

3. Duna

4. Pol or Bop

5. Laythe/Eeloo

I'm very sceptical if Tylo and Eve SSTOs are possible. Moho probably isn't possible without ion engines.

 

[Firemetal]

Just now, Matt Lowne said:

Mk2 is the most forgiving. 

With SSTOs, the best learning steps are:

1. Minmus

2. Mun/Gilly

3. Duna

4. Pol or Bop

5. Laythe/Eeloo

I'm very sceptical if Tylo and Eve SSTOs are possible. Moho probably isn't possible without ion engines.

 

I have landed on Minimus and Mun and "returned safely" (got dunked on ) so the next step is obviously Duna right? I thought Mk3 SSTOs would have more fuel but maybe I should go for mk2 instead.

Anyway thanks again! 

 

[Matt Lowne]

8 hours ago, Firemetal said:

I have landed on Minimus and Mun and "returned safely" (got dunked on ) so the next step is obviously Duna right? I thought Mk3 SSTOs would have more fuel but maybe I should go for mk2 instead.

Anyway thanks again! 

 

In general, yes, MK3 ships have more fuel, and so are more forgiving when in space since you have plenty deltaV to work around any mistakes. But Mk2 planes are much easier to fly and get into orbit initially, which is the hardest part of any mission imo

Edited July 10, 2016 by Matt Lowne

[Firemetal]

2 hours ago, Matt Lowne said:

In general, yes, MK3 ships have more fuel, and so are more forgiving when in space since you have plenty deltaV to work around any mistakes. But Mk2 planes are much easier to fly and get into orbit initially, which is the hardest part of any mission imo

Yup same with me. Next time I attempt a Duna SSTO, I'll make it Mk2.

Thanks!

[AeroGav]

The problem with mark 3 designs is that

a) the stock mk3 cockpit makes a good airliner or shuttle clone but is butt ugly imho, doesn't integrate asthetically with the hypersonic design

and b) none of the stock wings are big enough.   With procedural wings you could probably make something that looks and flies nice.

c) all of the fuselage diameter adapters are liquid fuel/oxidizer.   I don't generally use ox in an interplanetary ship, it's jet and nuke only

d) multiple fuel ducts to manage Centre of Gravity/feed all the engines really kill performance due to their bugged drag

For these reasons I stick with mk1 and 2.  Mk2 lacks lab and hab modules in stock, though i did download a "hypersonic" mk2 extension pack that included a very cool science lab (nice IVA too) in mk2 shape.    All I need now is a mk2 sleeper cab and we're good..

 

Horizontal landing on duna requires a lot of wing area, robust gear and some vernier thrusters to lower landing speed further into the acceptable range.

The same Vernier engines allow vertical landing on airless moons with very low gravity.

Generally I use my interplanetary spaceplanes in conjunction with ISRU, so fuel economy is not a concern.  It's cool having one big ship that can go almost anywhere , rather than a tiny capsule.  The only places I can't go are Tylo (TWR too low),  Eve (re-entry heat/TWR too low without jets) and Moho (well, possible with a ridiculous amount of refuelling, but impractical).

Duna touchdown with lots of wing and vernier.  This ship can SSTO to Duna and back unrefuelled, but clips an LV-N inside a rapier which is somewhat cheaty.

This is a larger plane landing on Duna 

..and the exact same aircraft can touchdown on minmus horizontally too.