Goliathud SSTO

[Pds314]

  On 6/19/2020 at 9:47 PM, SuicidalInsanity said:

Did some more optimization and tinkering based on the success everyone else has had with short and stubby vs long and managed to shave off almost 7 tons:

The Fat Sparrow - 36m/s left in the tank @ 81x80km orbit; 16,416 Funds, 22,227 kg Wet mass.
Only a single precooler as extra intakes are superfluous and saves on drag - it's not enough air for static full thrust, but by the end of the runway it's moving 150m/s and the precooler becomes more than sufficient for the Goliath. Got to 400m/s @9km before the 100 LF earmarked for the Goliath ran out and the Thuds lit.

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Wow that is extremely impressive. 22227 kg and you got to an 80 km orbit. Especially considering my failed attempt was over 8 tonnes heavier!

  On 6/19/2020 at 4:11 PM, Laie said:

 

Next up: trying something that actually carries payload. Double Goliaths, here I come.

ETA: hold on, one more...

23.8t -  50m/s in orbit - 550m/s@11km on jet power

 

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What is the name of this second vehicle? I am currently just calling it "Goliathud-Long-D3-derived craft" but that seems verbose and odd for a name to have a name in the name.

[Laie]

  On 6/20/2020 at 11:19 AM, Pds314 said:

What is the name of this second vehicle? I am currently just calling it "Goliathud-Long-D3-derived craft" but that seems verbose and odd for a name to have a name in the name.

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Thanks for considering it, but that was not supposed to be a proper submission, nor would it be fair to treat it as one. Once the propellant is spent, it's aerodynamically unstable in any attitude... I can't possibly land it, and don't believe anyone could. Unless you're willing to consider any landing one can walk away from?

[Pds314]

  On 6/20/2020 at 11:35 AM, Laie said:

Thanks for considering it, but that was not supposed to be a proper submission, nor would it be fair to treat it as one. Once the propellant is spent, it's aerodynamically unstable in any attitude... I can't possibly land it, and don't believe anyone could. Unless you're willing to consider any landing one can walk away from?

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Ok I guess I can remove it. It is one of the better craft though.

  On 6/18/2020 at 10:22 PM, SuicidalInsanity said:

I think this is just about as efficient as you can get: (Naturally, I fully expect to be proven wrong at some point).

17,592 Funds, 29.335 tons, 26 parts.
 

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Thought I'd try something different - instead of trying to gain speed on the jet and then switch to the Thud, my approach was to gain as much altitude as possible to try and get the best out of the Thud's sub-optimal performance.

The lack of intakes hurts initial accel, but can hit 140m/s by the end of the runway. The craft is light enough to actually slowly accelerate, even at ~30 deg pitch attitude.

The minimalist wing profile puts an upper limit on how high I can fly before atmo density becomes too thin to generate enough lift, so when the craft can no longer gain alt, the Thuds are lit.

Roughly ~81k by 70.5k orbit, with 9m/s to spare, though a better ascent profile should be able to improve that somewhat. Technically the current winner on kg of payload to permanent orbit at ~14.9 tons, since with only 9m/s dV left, it's not coming back down again.

 

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Can the One Way Trip land? At least in principle? Like, have you ever tried to land it?

 

I will be removing it from the leaderboard for now, as I can't see how it could even conceivably land recoverably and frankly I don't think it would even be stable without fuel.

Edited June 20, 2020 by Pds314

[Laie]

  On 6/20/2020 at 11:36 AM, Pds314 said:

Ok I guess I can remove it. It is one of the better craft though.

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Well, designing for only for ascent certainly made it easier. @swjr-swis added trailing tanks for CoM stability, for example, while I simply ignored the issue. He deserves a place of the leaderboard, but I don't. Working on it, though.

EDIT
Here we go: named Cargo-IVf2 for lulz and giggles, this probably demonstrates economies of scale more than anything else.

Cargo bay in the rear: The payload offsets the fuel mass, so the CoM is about in the same place going both ways. It shifts badly while the Thuds are running, but hey -- they're certainly not lacking in gimbal authority.

It barely manages to make orbit, after dropping the payload (which requires some wiggling) I've got a whopping 20m/s left for the de-orbit burn. Actually less: there is a fuell cell in the cargo bay, and I take great care to leave some vapors in the tanks so I won't run out of ElectricCharge on my way down.

Little detail: Tweaking the airbrakes I can hold almost any attitude. The PE was at 48km to begin with, but that kind of braking gets me back down quickly and decisively.

On my way to the landing I burned most remaining liquid fuel, in the belief that I might come up short. Then found myself divebombing for the KSC and touching down on the greens at more than 100m/s. Well, all in a day's work, I guess. A time lapse video is available for the seriously curious.

Mass at rollout: 130.361 - recovery: 38.571- payload: 17t

So I spent 74.79t in getting it to orbit. That's about 4.4kg of propellants per kg of payload, or 1136 grams-per-unit.

Edited June 20, 2020 by Laie

[SuicidalInsanity]

  On 6/20/2020 at 11:36 AM, Pds314 said:

Can the One Way Trip land? At least in principle? Like, have you ever tried to land it?

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Yes, in the sense all the material involved in it's construction will make it to the ground No. Not intact anyway, not with the rear landing gear where they are. TBH, I missed the landing part of the requirements the first time through, so it was designed purely for ascent  - trying to land it, the extreme CoM shift when dry caused it to helicopter its way down, ultimately splashing down at ~30m/s and exploding.

[swjr-swis]

This one was actually my first concept for this challenge, but it took me a good bit longer to optimize as I had my goal set on a payload that realistically exceeded the operational limits of this craft. I'm stubborn though, so here it finally is: The Thuliath Ib "Goose".

Specifications:

• Powered by one Goliath and four Thuds.
• Mk3 fuselage mid section, including two fuel tanks and a cargo bay.
• Single seat cabin.
• 37 parts, 21378 kg dry weight, 34315 funds.
• 49908 kg, 36906 funds fueled for this run.
• 54878 kg including payload.
• Operational limit of 4.5 t of payload to LKO and return (this run uses a 4.97 t payload).
• Exceeding operational payload limit is not recommended - margins are razor thin, and the ascent corridor allowing transition into supersonic is just decimals of a degree wide.
• With the proper ascent profile, moves into supersonic on a single Goliath alone, even at 55 t. Thuds are not engaged until 6km up and Mach 1.6+.
• CoM is balanced almost dead center on the cargo bay. The forward C7 adapter can be fueled for overweight payloads, which will shift the CoM forward; this does not compromise flight performance, and as it's prioritized to burn first, CoM quickly returns to its proper place.
• She can hold radial out on reentry down to about 40km, but take care to drop the nose close to prograde beyond that as there is a chance of getting into an uncontrolled tumble.

Fueled weight minus payload = 49908 kg.

Payload delivered: 4970 kg. Fuel used: (3110+3190) - (19.72+0) = 6280.28 units. Efficiency: 4970 / 6280.28 = 791 grams per unit.

Still stock 1.3.1, still no dV read out. Enough to drop Pe from 77km to 59km.

Pics or it didn't happen:

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Let's try with a 'proper' cargo bay. While I'm at it, let's see if I can once again mock the 'Mk3 is so draggy' crowd.

Wet weight minus the 4.97 t payload.

Ascent starts by skimming the waves until we pass Mach 1, then we engage SAS orbital prograde to follow the narrow slope that lets the Goliath keep climbing and accelerating.

Engaging the Thuds a bit before the Goliath is spent actually benefits our total fuel efficiency.

LKO with an overweight payload.

4.97 t of space station in orbit.

No expenses were spared to make this as functional a spaceplane as possible: antenna, batteries, solar panels and a radiator all included.

10 units of oxidizer lets us drop Pe from 77 to 59 km, which is plenty to stay in the atmosphere. We're coming home.

Oopsie, dropped too much airspeed too soon. But we have some fuel for the jet left, we can still take her in.

Soft touch down. We are home.

Full album: https://imgur.com/a/nPVZBel

Craft file: https://kerbalx.com/swjr-swis/Thuliath-Ib-Goose

[Pds314]

  On 6/21/2020 at 6:52 AM, swjr-swis said:

This one was actually my first concept for this challenge, but it took me a good bit longer to optimize as I had my goal set on a payload that realistically exceeded the operational limits of this craft. I'm stubborn though, so here it finally is: The Thuliath Ib "Goose".

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I'm somewhat surprised you managed to make it landable! Congrats though. So far among the entries that are in the lighter half, it has the best capabilities in orbit in terms of payload delivery or, if you replaced the payload with fuel, Delta-V.

[Pds314]

I have a preliminary entry. I'm not gonna add or name it yet, but I will say, it gets about 500 m/s in orbit in a 27-tonne craft with suboptimal piloting.

Edited June 21, 2020 by Pds314

[Laie]

This one works surprisingly well. Wing is way back to offset the Goliath torque (or it would flip), yet it's still controllable enough for a safe entry and return to the KSC. A soft and gentle landing at 40m/s, then a quick bounce and flip and sudden decrease in part count.

I guess I'll have to invest another 100kg in either training wheels on the wing tips, or a parachute or something.

The most interesting aspect is that slight shifts in CoM appears to matter *a lot*: several times I came up just a wee bit short to making orbit, then slipped in the donut tank, and on the next run I'd have twice the tank's contents left after circularization. So I guess I can make do without it, after all.

Edited June 21, 2020 by Laie

[Pds314]

Alright. The Vulture Thudgolion.
It's 22142 kg at launch and ends with 160 m/s of Delta-V in orbit.

Even though we are at over 150 m/s, we're still not at full power with just a precooler for an intake. We need to break 190 before that happens.


Breaking Mach 1.


Peak temperature on the Goliath. It's possible for this vehicle to explode its engine so it's best to be careful about climb rate. Don't climb too slowly.


About to engage the Thuds.


Disengaging Thuds. We're taking a fairly shallow trajectory to our Apokee.


And we're in stable orbit, if only by about 25 meters. We've got 160 m/s to spare. Plus a significant amount of maneuvering fuel left for the Goliath so we don't need to be too exact about our descent.

 

  On 6/21/2020 at 9:29 AM, Laie said:

This one works surprisingly well. Wing is way back to offset the Goliath torque (or it would flip), yet it's still controllable enough for a safe entry and return to the KSC. A soft and gentle landing at 40m/s, then a quick bounce and flip and sudden decrease in part count.

I guess I'll have to invest another 100kg in either training wheels on the wing tips, or a parachute or something.

The most interesting aspect is that slight shifts in CoM appears to matter *a lot*: several times I came up just a wee bit short to making orbit, then slipped in the donut tank, and on the next run I'd have twice the tank's contents left after circularization. So I guess I can make do without it, after all.

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Oh. Wow. You beat me in the time it took me to fly my plane I think...

[Pds314]

Managed a run with a partially-fueled Vulture Thudgolion without the nose boom tank.

20787 kg
5 m/s in orbit.
Splashed down instead of runway landing due to massively overshooting the runway after more than a full orbit in the atmosphere.

I'm also gonna remove my other Vulture Thudgolion run from the mass competition, as having 2 runs of almost identical craft at the top would be a bit silly.

Fully expect that it's possible to do a sub-20-tonne vehicle with good enough flying and design. Or maybe even just by using 1 thud. Afterall, that would improve the mass ratio and the aerodynamics and bring the weight down to 19887 kg for this craft.

Edited June 21, 2020 by Pds314

[swjr-swis]

  On 6/21/2020 at 11:55 AM, Pds314 said:

Managed a run with a partially-fueled Vulture Thudgolion

20787 kg
5 m/s in orbit.

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That general design can do even better, if the goal is just reaching LKO and landing. Under 20 t, 17 parts, single Thud. Allowed the use of a second precooler, both for intake air and for CoM balance.

You're right though, it's light enough for the Goliath to easily overheat if you don't climb fast enough. I did use a different control surface layout to improve roll control; made it easier on reentry and landing.

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I think it can still be improved a bit either way: add some more oxidizer and fuel for extra dV in orbit, or tweak the ascent profile to need less for barely making it, and lower its starting weight.

[Laie]

  On 6/21/2020 at 2:43 PM, swjr-swis said:

That general design can do even better, if the goal is just reaching LKO and landing. Under 20 t, 17 parts, single Thud. Allowed the use of a second precooler, both for intake air and for CoM balance.

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Oh boy, how do you even land? I guess I'm out. If that's what it takes... can't do.

[swjr-swis]

  On 6/21/2020 at 3:11 PM, Laie said:

Oh boy, how do you even land? I guess I'm out. If that's what it takes... can't do.

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Quite easily actually - it only weighs about 8.5t empty, and ends up pretty well balanced, which makes it surprisingly easy to glide in for a smooth landing. I was going as slow as 50 m/s and it was still not stalling. That landing gear may look fragile but it really doesn't need any more.

Just don't get nervous when you're almost down, any sudden control inputs can make that low tail hit the runway. Turning the Goliath upside down would allow some clearance to counter that risk, and it would have zero impact on its performance or control - but it would've affected the original concept a bit much.

 

[Pds314]

  On 6/21/2020 at 2:43 PM, swjr-swis said:

 

That general design can do even better, if the goal is just reaching LKO and landing. Under 20 t, 17 parts, single Thud. Allowed the use of a second precooler, both for intake air and for CoM balance.

You're right though, it's light enough for the Goliath to easily overheat if you don't climb fast enough. I did use a different control surface layout to improve roll control; made it easier on reentry and landing.

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I think it can still be improved a bit either way: add some more oxidizer and fuel for extra dV in orbit, or tweak the ascent profile to need less for barely making it, and lower its starting weight.

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I like the way you did the tail on that one. And wow it's light. Much lighter and we'll be able to launch it from level 1 facilities.

[swjr-swis]

  On 6/21/2020 at 8:59 AM, Pds314 said:

So far among the entries that are in the lighter half, it has the best capabilities in orbit in terms of payload delivery or, if you replaced the payload with fuel, Delta-V.

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I decided to give that a try. Replaced the payload with two tanks and fully fueled up the plane for a test run in KSP 1.9.1. End result: 777 m/s dV left in LKO.

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A test run in 1.9.1 to measure dV margin. Payload replaced by two LFO tanks and plane fuel maxed.

Acceleration is abysmal, and breaking Mach 1 on just the Goliath becomes impossible.

Since supersonic on jet alone wasn't going to happen, I just burned off the excess LF, climbed to a higher altitude, and ignited the Thuds for the ascent.

Very steep climbing angle to keep the Goliath from exploding.

Ap established, minimal burn needed to circularize.

LKO with 777 m/s left in the tanks.

This Goose is going on a trek.

 

[swjr-swis]

  On 6/17/2020 at 10:31 AM, Pds314 said:

swjr-swis, 19762 kg, Thuliath Pds

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You listed that one under my name, but I was just testing what your design could do with a few tweaks. It's your craft.

[Lt_Duckweed]

Please give a warm welcome to "Mr. Oneupsmanship", which has been very deliberately positioned at exactly 25kg lighter than the currently lightest entry.

Mass: 19,737 kg wet, 9,475 kg dry

Lf/Ox mix: 10,000 kg full, 26.4 kg remaining in orbit

Liquid fuel: 200 kg full, 4.55 kg remaining in orbit

Dv left in orbit: 8 m/s

Edited June 24, 2020 by Lt_Duckweed

[Lt_Duckweed]

In a stunning turn of events, Mr Oneupsmanship 3 was revealed so quickly, that Mr Oneupsmansip 2 never even got a chance to launch.  This craft improves on the original by shaving 1.2 tons of dry mass.

Mass: 18,537 kg wet, 8,295 kg dry

Lf/Ox mix: 10,000 kg full, 332.25 kg remaining in orbit

Liquid fuel: 200 kg full, 39.65 kg remaining in orbit

Dv left in orbit: 117 m/s

 

Parts replaced/removed are:

Mk1 Inline Cockpit + Aerodynamic Nosecone -> Mk1 Command Pod + Small Nosecone: 220 kg saved

2x Circular Intake -> 2x Aerodynamic Nosecone: 40 kg saved

2x Elevon 4 pitch surfaces -> 1x Elevon 4 pitch surface: 40 kg saved

2x Thud -> 1x Thud: 900 kg saved

Edited June 24, 2020 by Lt_Duckweed

[Lt_Duckweed]

Third and final update of the night.  By swapping my intake/liquid fuel storage setup from one precooler to a partially filled Mk0 tank and replacing two aerodynamic nosecones with circular intakes, and also getting rid of my roll control surfaces, I was able to trim another 215 kg off of the craft.

Mass: 18,322 kg wet, 8,295 kg dry

Lf/Ox mix: 10,000 kg full, 252.9‬ kg remaining in orbit

Liquid fuel: 175 kg full, 23.8‬ kg remaining in orbit

Dv left in orbit: 91 m/s

[Pds314]

I will add the new entries later. And wow. Only 322 kg away from being able to launch on an unupgraded runway.