Goliathud SSTO

[Pds314]

Mission

This challenge is to create, fly, and land a crewed SSTO using quite possibly the worst engines for the job. Specifically, the Goliath and the Thud.

There will be three categories:

1. Minimum mass

(How light can you make your SSTO?)

1. swjr-swis, 19762 kg, Thuliath Pds
2. Pds314, 20787 kg, Vulture Thudgolion 2.0
3. SuicidalInsanity, 22227 kg, Fat Sparrow
4. swjr-swis, 29407 kg, Thuliath Vc2 "Vicissitude"
5. Laie, 31060 kg, Goliathud-Long-D3
6. swjr-swis, 49908 kg, Thuliath Ib "Goose"
7. Laie, 60400 kg, a data point
8. Sevenperforce, 60800 kg, Goliathud X
9. Laie, 130621 kg, Cargo-IVf2
10. ralanboyle, 149000 kg, Goliathud 1

2. Fuel economy

(kg of payload put in permanent orbit per unit of fuel plus oxidizer spent putting it there).

1. Laie, 1136 grams/unit, Cargo-IVf2
2. swjr-swis, 791 grams/unit, Thuliath Ib "Goose"
3. swjr-swis, 339 grams/unit, Thuliath Vc2 "Vicissitude"

3. Range

(how much Delta-V do you have once in orbit?)

1. ralanboyle, 756 m/s, Goliathud 1
2. Sevenperforce, 268 m/s, Goliathud X
3. Laie, 227 m/s, a data point
4. Pds314, 160 m/s, Vulture Thudgolion 1.0
5. SuicidalInsanity, 36 m/s, Fat Sparrow
6. Laie, 17 m/s, Goliathud-Long-D3
7. Pds314, 5 m/s, Vulture Thudgolion 2.0

Oh, and no command chair. Use a proper cockpit. Also please use both engine types. No pure Thud SSTOs.

Edited June 21, 2020 by Pds314

[Superfluous J]

I'm not going to enter this contest as I can't even make a normal SSTO (well, a normal plane SSTO) but I want to give more kudos than the "thumbs-up" allows for the name "Goliathud"

[Pds314]

My failed attempt, the Chubby Catfish. Maybe with better piloting it could achieve orbit. It never even reached mach 1 under pure jet power.

Weight: 30400 kg.
LF/O load: 3700 units.
Payload: 0 kg.
Delta-V in orbit: -140 m/s (140 m/s short of reaching orbit).

Edited June 17, 2020 by Pds314

[sevenperforce]

I have so much trouble with yaw authority on the runway, on almost all of my designs.

[doggonemess]

I used to have that problem a lot, and a big part of it seemed to come from the landing gear. One thing I always do is switch to the rotate tool, set it to absolute, and move the wheel off-axis and back in all three orientations. For some reason, that works for me most of the time. Other than that, sometimes switching the controls to 'fine' using CapsLock helps.

EDIT: OH, and one other thing. If you turn off engine gimballing it can help. Tie it to a control key and turn it back on once you're in the air.

Edited June 17, 2020 by doggonemess

[sevenperforce]

I made it to LKO easily enough once I was able to get off the runway in one piece, but the Goliath was useless. Basically I just made a Thud-based SSTO that carries a Goliath along for the ride.

5 minutes ago, doggonemess said:

OH, and one other thing. If you turn off engine gimballing it can help. Tie it to a control key and turn it back on once you're in the air.

Engine gimbal with the Thuds was the only way I was able to get off the ground at all.

[doggonemess]

2 minutes ago, sevenperforce said:

I made it to LKO easily enough once I was able to get off the runway in one piece, but the Goliath was useless. Basically I just made a Thud-based SSTO that carries a Goliath along for the ride.

Engine gimbal with the Thuds was the only way I was able to get off the ground at all.

Huh. I figured that the gimbal was hurting ground controllability. Interesting.

[sevenperforce]

Here's my entry -- the Goliathud X.

Weighs in at 60.8 tonnes.

You'll notice that I made use of the attachment node on the front of the Goliath. Having a bare 2.5-m face was going to produce ridiculous levels of drag, so I utilized four air intakes instead. The shock cone intakes don't have enough static suction, so I added two basic air intakes at the rear of the main rocketfuel tanks. They are just slightly heavier than a small nose cone but have less drag, so it was worth it.

I also had to use large landing gear due to the significant weight of the vehicle, which I didn't like, but oh well.

Spoiler

Starting down the runway. With the weight characteristics and low wing area of this craft, the Goliath won't get me going fast enough to get off the ground by the end of it.

Once I start to yaw, I fire up the Thuds (with a reaction group) to give me a boost off the runway.

Safely in the air.

I shut off the Thuds and raised the gear. Now the goal is to get whatever use I can out of the Goliath. Speed is more important than altitude...particularly because the Goliath loses thrust relative to altitude faster than it gains relative to speed. The faster I'm going, the more dV I can squeeze out of the Thuds when I pitch up.

The goal is to maintain positive velocity growth without losing too much altitude.

I started losing speed, so I pitched back down.

Finally starting to level out, dangerously low. I will build up as much speed as I can and then fire up the Thuds.

Looks to be reaching my limit.

Thuds are ignited and I'm pitching up to gain altitude quickly.

I might have been able to get away with just four Thuds but having six really helps with thrust.

The Goliath has flamed out at this point.

I've got sufficient speed to make my apoapsis, so I cut throttle to ultra-low and I'm coasting.

Now that I'm out of most of the atmosphere, I can pitch down and burn gradually for orbit.

Almost there. Warping around.

And there's my orbit, with a "whopping" 268 m/s of dV remaining.

 

[Pds314]

8 hours ago, sevenperforce said:

I have so much trouble with yaw authority on the runway, on almost all of my designs.

Make sure landing gear are aligned. Also reduce the friction control of the front landing gear. Finally, always use a steerable landing gear for the nose gear (in tricycle designs) or the tail gear (in taildraggers) and don't try to use one for any other part of the plane. It's better to double up steerable gears if you have to and increase their spring strength than it is to use unsteerable gears for nose or tail wheels.

Also it's a bit floppy but I've had some success with using Breaking Ground servos as landing gear steering controls for the larger gears.

Edited June 18, 2020 by Pds314

[sevenperforce]

14 hours ago, Pds314 said:

Make sure landing gear are aligned. Also reduce the friction control of the front landing gear. Finally, always use a steerable landing gear for the nose gear (in tricycle designs) or the tail gear (in taildraggers) and don't try to use one for any other part of the plane. It's better to double up steerable gears if you have to and increase their spring strength than it is to use unsteerable gears for nose or tail wheels.

I always align my landing gear correctly, but I will try the friction control changes and see if that makes a difference. Usually I just end up adding more vertical stabilizers but that's a painful way of doing it. 

And my large nose gear was unsteerable so that might have contributed too.

[ralanboyle]

Alright, 

Goliathud 1 Weighs 149T, but she has 756 m/s dv left at orbit. 

 

[Laie]

Different philosophies, similar outcomes... this one masses 60.4t at rollout and has 227m7s left in orbit. It's not meant as a proper submission, more a data point.

I gave up on going supersonic. My fastest plane managed 360m/s in level flight, but even the slightest amount of climb would ruin it. The fastest practical speed appears to be 300m/s or so -- but I noticed that I can maintain that velocity until 5km or more.

With only one intake, the Goliath is starved for air until 150m/s, and it barely reaches 70m/s by the end of the runway. That's enough for takeoff, though, and the plane goes up to 290m/s@6km before I turn on the Thuds with an ISP of 295s. The I pull up and, well, essentially that's it. AoA reaches 10° at some point, and due to the low-heat wings I have to pull up harder and longer than usual, reaching 1800m/s@40km. But never mind, she makes it.

I'll try shuttle wings tomorrow. And maybe more Thuds.

[Cavscout74]

@Laie it never occurred to me to use a Goliath for the tail of a plane.  I may have to steal that idea to use on something.  I'm not sure what to use it on yet, but the gears have started turning.....

[sturmhauke]

It's possible to go supersonic with Goliaths on a conventional aircraft, at least, but the problem is they start to overheat around Mach 1. You can mitigate it a bit with creative use of precoolers or radiators, but of course they add mass and drag.

[SuicidalInsanity]

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.
 

Spoiler

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.

 

Edited June 18, 2020 by SuicidalInsanity

[sevenperforce]

19 hours ago, ralanboyle said:

Alright, 

Goliathud 1 Weighs 149T, but she has 756 m/s dv left at orbit. 

I see that you too found a need to fire the Thuds on the runway.

Do you think you could have used the Goliaths without them to get more altitude and speed once airborne?

19 hours ago, Laie said:

Different philosophies, similar outcomes... this one masses 60.4t at rollout and has 227m7s left in orbit. It's not meant as a proper submission, more a data point.

I gave up on going supersonic. My fastest plane managed 360m/s in level flight, but even the slightest amount of climb would ruin it. The fastest practical speed appears to be 300m/s or so -- but I noticed that I can maintain that velocity until 5km or more.

With only one intake, the Goliath is starved for air until 150m/s, and it barely reaches 70m/s by the end of the runway. That's enough for takeoff, though, and the plane goes up to 290m/s@6km before I turn on the Thuds with an ISP of 295s. The I pull up and, well, essentially that's it. AoA reaches 10° at some point, and due to the low-heat wings I have to pull up harder and longer than usual, reaching 1800m/s@40km. But never mind, she makes it.

I'll try shuttle wings tomorrow. And maybe more Thuds.

Very nice, clean planform. You've got me beat on mass barely but I think I have a touch more dV.

18 hours ago, Cavscout74 said:

@Laie it never occurred to me to use a Goliath for the tail of a plane.  I may have to steal that idea to use on something.  I'm not sure what to use it on yet, but the gears have started turning.....

I didn't know until I did it that the Goliath has a shroud on the front if you attach a 2.5-m part.

16 hours ago, SuicidalInsanity said:

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.

Very interesting design! I think you definitely saved on weight by doing it this way, but less payload for sure.

[Laie]

2 hours ago, sevenperforce said:

Very nice, clean planform. You've got me beat on mass barely but I think I have a touch more dV.

You're missing the point: for each and every decision of yours, I did the opposite... yet the results are virtually the same. That wasn't the plan, of course, but it's how it came out. I think that's funny.

18 hours ago, SuicidalInsanity said:

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

Yes, I think that's perfectly sensible. It may be a question of sheer energy, kinetic vs. potential -- though I generally don't think it's worthwhile to push supersonic through the lower atmosphere, certainly not on rocket power.

Another attempt, and this one actually goes supersonic -- why trade speed vs altitude if you can have both?

31,060kg, 17m/s left.

I brought too little jet fuel, otherwise it would certainly have gone up to something like 550m/s. As it was, I had to kick in the Thuds when the Goliath had run through it's alloted amount. All things considered, I'm afraid that this may be too much wing. I'm not certain that give or take 50m/s or 1km of altitude are really worth the drag later in the flight.

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

 

Edited June 19, 2020 by Laie

[ralanboyle]

4 hours ago, sevenperforce said:

I see that you too found a need to fire the Thuds on the runway.

Do you think you could have used the Goliaths without them to get more altitude and speed once airborne?

Yes, my design can be run more efficiently, and it now has but I moved on to other challenges and can't be bothered to make a new video...

[swjr-swis]

On 6/17/2020 at 12:31 PM, Pds314 said:

This challenge is to create, fly, and land a crewed SSTO using quite possibly the worst engines for the job. Specifically, the Goliath and the Thud.

Create, fly, and land. Check.

On 6/17/2020 at 12:31 PM, Pds314 said:

Oh, and no command chair. Use a proper cockpit. Also please use both engine types.

No command chair: crewed Mk1 cockpit. Both engines used: 1x Goliath, 2x Thud.

 

Spoiler

Net weight of the craft mission-ready, without the payload: 29407 kg.

Payload is an ion-powered relay satellite weighing 1129 kg.

1x Goliath, 2x Thud. There is also a small RCS capability for payload delivery, but it's not required or used to reach orbit.

The Vicissitude is streamlined enough to take off and move supersonic on Goliath power alone.

Not entirely done climbing or accelerating, but we want to move on to orbit now. Time to engage the Thuds.

80x80km orbit reached, payload delivered. There's still enough fuel left to return home.

Aerobraking helps if we are overshooting or if we spent too much fuel on ascent.

And touchdown. Safely back to the KSC.

Full album: https://imgur.com/a/K6oCzA3

Craft file: https://kerbalx.com/swjr-swis/Thuliath-Vc2

 

On 6/17/2020 at 12:31 PM, Pds314 said:

How light can you make your SSTO?

29407 kg fueled, minus payload.

 

On 6/17/2020 at 12:31 PM, Pds314 said:

(kg of payload put in permanent orbit per unit of fuel or oxidizer spent putting it there)

The 'or' in this phrase implies it's optional which one to use for the calculation, in which case I pick LF (1568 of 2280 units tank space used). 1129 kg relay satellite payload lifted to space. 1129/1568=0.72 kg/u.

 

On 6/17/2020 at 12:31 PM, Pds314 said:

how much Delta-V do you have once in orbit?

Hmm, I can't see this on KSP 1.3.1 stock. Enough to return to KSC and land. Just under 31 units of O plus some excess LF.

 

[sevenperforce]

1 hour ago, swjr-swis said:

The Vicissitude is streamlined enough to take off and move supersonic on Goliath power alone.

Very very impressive job.

I see you also made use of reversed air intakes.

[swjr-swis]

1 minute ago, sevenperforce said:

I see you also made use of reversed air intakes.

I did. The static intake of the two precoolers falls just a bit short of what the Goliath needs at stand-still. The two intakes are almost as good a drag end as the nose cones, plus they give some extra powerful static intake for the start of the roll. Once at speed they do nothing anymore, but by then the precoolers are delivering all the air the Goliath needs.

[SuicidalInsanity]

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.

Edited June 19, 2020 by SuicidalInsanity

[Pds314]

16 hours ago, swjr-swis said:

Create, fly, and land. Check.

No command chair: crewed Mk1 cockpit. Both engines used: 1x Goliath, 2x Thud.

 

  Hide contents

Net weight of the craft mission-ready, without the payload: 29407 kg.

Payload is an ion-powered relay satellite weighing 1129 kg.

1x Goliath, 2x Thud. There is also a small RCS capability for payload delivery, but it's not required or used to reach orbit.

The Vicissitude is streamlined enough to take off and move supersonic on Goliath power alone.

Not entirely done climbing or accelerating, but we want to move on to orbit now. Time to engage the Thuds.

80x80km orbit reached, payload delivered. There's still enough fuel left to return home.

Aerobraking helps if we are overshooting or if we spent too much fuel on ascent.

And touchdown. Safely back to the KSC.

Full album: https://imgur.com/a/K6oCzA3

Craft file: https://kerbalx.com/swjr-swis/Thuliath-Vc2

 

29407 kg fueled, minus payload.

 

The 'or' in this phrase implies it's optional which one to use for the calculation, in which case I pick LF (1568 of 2280 units tank space used). 1129 kg relay satellite payload lifted to space. 1129/1568=0.72 kg/u.

 

Hmm, I can't see this on KSP 1.3.1 stock. Enough to return to KSC and land. Just under 31 units of O plus some excess LF.

 

That is very impressive. However, that's not what I meant by "OR." I guess really I meant "AND" or rather "PLUS."

 

OK so this challenge kinda exploded over the past like.. day and a half. I'm gonna start putting the entries on the OP.

Edited June 20, 2020 by Pds314

[Pds314]

On 6/18/2020 at 1:00 PM, sturmhauke said:

It's possible to go supersonic with Goliaths on a conventional aircraft, at least, but the problem is they start to overheat around Mach 1. You can mitigate it a bit with creative use of precoolers or radiators, but of course they add mass and drag.

Yes you can do over mach 2 but they overheat very badly.

[Laie]

16 hours ago, swjr-swis said:

Full album: https://imgur.com/a/K6oCzA3

Whoa! I had no idea that Goliths can go *that* fast.

3 minutes ago, Pds314 said:

Yes you can do over mach 2 but they overheat very badly.

Gaining altitude helps with that. 450m/s gets hot at 5km, but higher up it cools down again. Not enough data to be sure, but I think at 10km you can cruise at any speed.