Razor Resurrect

[Armanix]

Hello! This challenge isn't originally mine, originating from lordburgerr on the r/

Basic premise is to build a rocket within the limit of 4 squares wide that can go to mercury and back. My personal edit for this challenge due to it previously being made for 1.35* is as such.

You are to restrict the build to a single launch, no cheats, no refuel, no launchpad assembly. 1 shot, mercury and back. Drag must be enabled (I make qks, quit, resume, load, quit and resume again just to make sure)

Easy mode: any part that conforms to the 4 wide limit may be used, solar panels and legs may extend beyond. Note: Titan engine is 4 and a half blocks (ish) and cannot be used.

Hard mode: (this is specifically to recreate handicaps of 1.35* when the challenge was posted) propulsion is limited to hawk,broadsword,grasshopper and ions. (This version didn't have adapting parts so the frontier was too big) You cannot activate an engine if the nozzle is directly attached to another part. The amount of spacing doesn't matter as long as there is a gap between nozzle and part it can be used. The mission is required to be manned. Panels and legs may still extend beyond 4wide as long as they are within the limit stowed.

Link to original
https://www.reddit.com/r/SpaceflightSimulator/comments/95jjpj
*I believe 1.35 is the correct notation of the version, it's been awhile since then. Regardless, set limits are correct.

 

[TtTOtW]

1.35

 

[8BitCosmonaut]

and a word from our sponsor

 

[Blazer Ayanami]

The amount of spacing doesn't matter as long as there is a gap between nozzle and part it can be used.

But there's no way to do this without breaking the limit of 4-wide

 

[Horus Lupercal]

Mercury return journey, single launch, 2 metres wide.

Let's look at this then.

Looking at the original Reddit challenge

• Hard mode isn't achievable. The 1.35 engines ain't powerful enough.
• Normal is a pointless rule, as what are you going to dock with if you're not allowed to launch anything else?
• Easy is too easy. Multi launch and dock, you can lift as much stuff as you'd like in single launches, dock them together, re-fuel, whatever and fly to Mercury, re-fuel after landing and fly back.

So, I've gone for a 1.4 Hard mode. One launch, no docking, 1.4 versions of 1.35 only engines

Titan is banned, and you're not allowed to multi-launch. The most powerful engine you can use is Hawk, which limits the max launch weight to 115t. Inside that, you need to generate (according to the Dv Map) 7,500m/s of Dv.

Chemically, that just isn't do-able. The lightest I got it down to with nothing more than a capsule on top is 197tons, 4 stages.

Electric it is then...

This 'beauty' should be capable of a single launch Mercury return landing, no re-fuel.

On one condition. You follow the fuel tank weights below exactly.

From bottom to top, you drain the first stage engine to 75%, second stage to 82%. Then the bottom 5t tank to 82% and the top one to 48% (exact totals shown in row M).

This will give you the 7585m/s required to get to Mercury using Altaïr gravity assist route and return coming the same route and an Earth atmosphere aero-brake with some fudge built in as well. You can even leave the 5t tanks about 90% full if you want as well if you're worried about getting home.

 

[Blazer Ayanami]

Mercury return journey, single launch, 2 metres wide.

Let's look at this then.

Looking at the original Reddit challenge

• Hard mode isn't achievable. The 1.35 engines ain't powerful enough.
• Normal is a pointless rule, as what are you going to dock with if you're not allowed to launch anything else?
• Easy is too easy. Multi launch and dock, you can lift as much stuff as you'd like in single launches, dock them together, re-fuel, whatever and fly to Mercury, re-fuel after landing and fly back.

So, I've gone for a 1.4 Hard mode. One launch, no docking, 1.4 versions of 1.35 only engines

Titan is banned, and you're not allowed to multi-launch. The most powerful engine you can use is Hawk, which limits the max launch weight to 115t. Inside that, you need to generate (according to the Dv Map) 7,500m/s of Dv.

Chemically, that just isn't do-able. The lightest I got it down to with nothing more than a capsule on top is 197tons, 4 stages.

Electric it is then...

View attachment 28399

This 'beauty' should be capable of a single launch Mercury return landing, no re-fuel.

On one condition. You follow the fuel tank weights below exactly.

View attachment 28400

From bottom to top, you drain the first stage engine to 75%, second stage to 82%. Then the bottom 5t tank to 82% and the top one to 48% (exact totals shown in row M).

This will give you the 7585m/s required to get to Mercury using Altaïr gravity assist route and return coming the same route and an Earth atmosphere aero-brake with some fudge built in as well. You can even leave the 5t tanks about 90% full if you want as well if you're worried about getting home.

So the Ions will lift her from Mercury? I've never thought that would possible.

 

[Horus Lupercal]

So the Ions will lift her from Mercury? I've never thought that would possible.

Mercury gravity is a 3rd of what it is here. Even with a full 5t tank, it'll still lift from Mercury with one ion engine. Although, I've had to do some weight saving tricks like leaving the landing legs and empty tank behind and launching the top section a la LM.

 

[Horus Lupercal]

Got to Mercury without much hassle, and plenty of fuel left thanks to Altaïr slingshot route.

But now I have a huge problem. As Blazer pointed out, Ions don't have much thrust but that is offset by Mercurys' very low gravity when it comes time for take-off and I've calculated that even full, the top half of the MM (Mercury Module) will lift off the surface once detached.
However, landing is a whole different ballgame.
I knew a hoverslam was always going to be out of the question because just no but figured a long, slow burn from orbit and gradually touch down would work as I've got the Dv to spare.

Nyet.

Not only am I fighting local gravity, but also the orbit which is accelerating me even faster from apo to peri (i.e, the ground as the periapsis is sub-surface). That is over matching the Ions to the point where no matter what I do once I get low enough and decelerate below 350ishm/s, I then start accelerating and generally strike the ground at about 450m/s, even if I ditch everything.

The theoretical deductions from this are obvious. NEED MOAR POWAAAARRR.

The practical application is however much more difficult. The most suitable engine is the Grasshopper, and it only weighs 0.5t so it's not much extra mass to lift and shouldn't be an issue getting into LEO and then onto LMO.

The problem comes with adding a grasshopper engine in a realistic landing configuration inside a 2 metre width restriction.
The engine must sit on the 4 wide tank.
The legs can't go under the engine as nothing is allowed to be attached to the cone.
It can't go on the side of the tank as that breaks the width limits
And it looks like this if you place it over the tank...

There's no part clipping when they lower and extend.

Instead they just don't make contact with the ground.

So, playing with a few configurations and little ways of attaching the legs lower than the engines resulted in this:

Which is aerodynamic enough to be launched, but ground testing revealed the narrow leg stance when unfolded mean it was too unstable for practical use. And it's technically not legal because it's 2.5m wide with the leg securing parachutes.
Thus, the drawing board was returned to.

And several hours later, I've decided on a plan.

Fuck the 2 metre rule.

It's a good plan and I'm sticking with it.

I'll finish the payload tomorrow.

 

[Blazer Ayanami]

Got to Mercury without much hassle, and plenty of fuel left thanks to Altaïr slingshot route.

View attachment 28475

But now I have a huge problem. As Blazer pointed out, Ions don't have much thrust but that is offset by Mercurys' very low gravity when it comes time for take-off and I've calculated that even full, the top half of the MM (Mercury Module) will lift off the surface once detached.
However, landing is a whole different ballgame.
I knew a hoverslam was always going to be out of the question because just no but figured a long, slow burn from orbit and gradually touch down would work as I've got the Dv to spare.

Nyet.

Not only am I fighting local gravity, but also the orbit which is accelerating me even faster from apo to peri (i.e, the ground as the periapsis is sub-surface). That is over matching the Ions to the point where no matter what I do once I get low enough and decelerate below 350ishm/s, I then start accelerating and generally strike the ground at about 450m/s, even if I ditch everything.

The theoretical deductions from this are obvious. NEED MOAR POWAAAARRR.

The practical application is however much more difficult. The most suitable engine is the Grasshopper, and it only weighs 0.5t so it's not much extra mass to lift and shouldn't be an issue getting into LEO and then onto LMO.

The problem comes with adding a grasshopper engine in a realistic landing configuration inside a 2 metre width restriction.
The engine must sit on the 4 wide tank.
The legs can't go under the engine as nothing is allowed to be attached to the cone.
It can't go on the side of the tank as that breaks the width limits
And it looks like this if you place it over the tank...

View attachment 28476

There's no part clipping when they lower and extend.

View attachment 28477

Instead they just don't make contact with the ground.

So, playing with a few configurations and little ways of attaching the legs lower than the engines resulted in this:

View attachment 28478

Which is aerodynamic enough to be launched, but ground testing revealed the narrow leg stance when unfolded mean it was too unstable for practical use. And it's technically not legal because it's 2.5m wide with the leg securing parachutes.
Thus, the drawing board was returned to.

And several hours later, I've decided on a plan.

Fuck the 2 metre rule.

It's a good plan and I'm sticking with it.

I'll finish the payload tomorrow.

How about if you skip the landing legs and land on top of a 4 wide docking port.

I've used this before, on Ganymede. It works.

 

[TtTOtW]

In 1.35 the side parachutes fitted inside the 4w fairing, so that's an exploit I'd be willing to support.

 

[Blazer Ayanami]

You know, I'll give this a new try. On my previous attempt I almost succeed, but had the same problem as Horus: couldn't land because of the low TWR on the landing stage.

 

[Hossa]

I like this challenge. I know what I’ll be wasting time at work with.

 

[Hossa]

Just so I understand the challenge, go to Mercury and back using a single stack rocket no wider than 4 squares in a single launch without using Titan engines? Did I miss anything?

 

[Blazer Ayanami]

Just so I understand the challenge, go to Mercury and back using a single stack rocket no wider than 4 squares in a single launch without using Titan engines?

Correct

Did I miss anything?

You can't activate an engine if the exhaust is directly attached to other part.

 

[TtTOtW]

And no frontier engines

 

[Horus Lupercal]

And no frontier engines

You can use frontier if you're going for easy mode

 

[Horus Lupercal]

Right, take 2

This is the MEM (Mercury Excursion Module)

Features (from top to bottom) the 1 man CM, power and fuel for the return flight, the lander section with grasshopper and landing legs and the outbound Ion engine.

Then a very basic launch vehicle to get it up to LEO

Why 3 stages?

Cos I can. That's why.

Still got some juice in the the 3rd stage to be going with.

 

[Asgad]

I don't think 115 t is the upper limit. You can create more thrust, see examples attached.

 

[Asgad]

If we agree *half* the exhaust may be blocked, we can even do this:

 

[TtTOtW]

I don't think 115 t is the upper limit. You can create more thrust, see examples attached.

I did try that, but the aerodynamic penalty is stupid. Not worth the extra thrust.

 

[Blazer Ayanami]

I did try that, but the aerodynamic penalty is stupid. Not worth the extra thrust.

then it should work in space.

 

[Asgad]

Yeah, but TtTOtW is right - they would only make sense during the start.

 

[Horus Lupercal]

I don't think 115 t is the upper limit. You can create more thrust, see examples attached.

Your conclusion is correct but your methods are flawed.

You can stack grasshoppers that way, but you'd need a lot of them to generate the same thrust as a single hawk.
The other issue is TWR. Hawk is superior to grasshopper in every metric and adding more grasshoppers with the relevant attachments will add thrust but not as much actual TWR, which with the turd specific impulse, means you need to add more fuel which further compounds the problem.

The cycle of that is you need a bigger rocket to lift the same weight to the same location.

Add, as TtTOtW right says, the additional drag penalty of lots of engines, structural attachments etc, is it really beneficial?

And i say this as the grasshopper engines biggest cheerleader on the forum, but it's not a viable heavy lift engine under any but the most outrageous (Hoppy) circumstances.

What is possible though if you wish to stack engines, is stack a more useful engine like Hawk, each with 40t of fuel on them as like a vertical stack booster keeping in line with the wording of the rules if not the spirit and actually contributing to the overall TWR if you really need moar weight.

Have say 3 of them as your 'first stage', 2 in the 'second'. You'll be able to lift about 340-350t off the pad, and probably put...80t into LEO. You could probably go chemical all the way to mercury and back with a broadsword then, but you'd still have the same width restrictions with landing leg placement.

then it should work in space.

It would work, but you know that grasshopper is as bad as Titan as a vacuum only engine and the fuel requirements would horrifying down to Mercury

 

[Hossa]

Achieved. It was hard. But I made it after much testing.

 

[Hossa]

1 moon assist, 1 Earth assist, a couple Venus assists and a couple Mercury assists before I touched down. Using only the cricket engine for landing of Mercury and takeoff. Everything else was the ion. I had 39 percent fuel when landed. It took 35 percent to get back with only 1 Venus assist on the way back.