Non-RO launch vehicles for RSS

[Pds314]

On 5/18/2020 at 7:32 AM, Laie said:

Been trying to solve this on paper...

LEO(KSC 23°)-> Geo requires about 4200m/s, with 20t payload and lots of nuke power I end up with 60t gross mass for that part of the mission.

Below that, a Rhino upper stage with 4Min burn time, starting at TWR 0.87 for 3200m/s. Still reasonable.

And then Tsiolkowski beats down hard: wrapping the above in eight Mammoths isn't quite enough, dV-wise, and TWR would be abysmal throughout. I'm used to RO launches where you'd reach 3-5g at the end of each stage, and have no idea how it would work out with an asparagus design that hardly ever reaches 2g. My guess is that it would require more like 12km/s to make orbit, rather than the 9+km/s I'm used to.

In a nutshell, I don't think it's worthwhile to use stock parts in a RSS setting. The good old MOAR approach will eventually get you there, but it's not the kind of challenge I'd enjoy.

I mean, my rocket uses a vaguely similar configuration but without nukes and doesn't require anything like 12 km/s of Delta-V to get to orbit but 9.0 vacuum equivalent, which means less than 9 in reality. I'm not 100% sure how much it actually uses because I'm staging during a burn and the readout for the quad-Rhino core stage is not seeing anything above the adapter as part of the stage, but to get an 80.5 tonne payload into orbit it's taking 6000 tonnes with no asparagus or drop tanks.

Edited May 20, 2020 by Pds314

[Pds314]

I didn't manage to achieve quite geostationary, but pretty close. If I had launched from 28 degrees North Cape Canaveral, Florida, USA, instead of 39.6 degrees latitude in Sohae, Democratic People's Republic of Korea, I would definitely have gotten it with Delta-V to spare.

Payload: 20000 kg of ore tanks, 80 kg of control equipment. 20080 kg.

Final orbit:
Inclination: 8.9 degrees.
Eccentricity: 0.0078.
Periapsis: 35,198,234 meters.
Apoapsis: 35,850,465 meters.
Orbital period: 23 hours, 42 minutes, 21 seconds.
Longitude of Ascending node: 92.5 degrees.
Arg of Periapsis: 182.6 degrees.
Current Longitude: -48, off the cost of Brazil. Nowhere near Korea...

Actual launch:

We have liftoff. Status is nominal.

 

 

Spoiler added to reduce page download size.

Spoiler

Initiate gravity turn at 100 m/s and aggressively turn over by 10 degrees.


Core stage ignition at 12.5 km.


Booster separation confirmed at 23 km.


Lock orientation above prograde to aim the liquid fuel boosters at Japan avoid overrunning our apoapsis too early.


Liquid-fuel booster separation complete, fairing fragmentation complete.


1 minute, 40 seconds to Apogee at 147 km.


Core stage is 8 seconds from burnout, not 1.


Upper stage is 4 seconds from stable orbit.


Stable orbit achieved.


Orbit is 193*159 km above sealevel. Plot a course for GTO.


Burn upper stage until it's out of fuel.


Burning GEO transfer drop tanks 5 and 6.


Separation of tanks 5 and 6.


Separation of tanks 3 and 4.


Overshot GTO by 64 km.


Planning a burn to an 8.9-degree inclined GEO.


Burning GEO transfer drop tanks 1 and 2.


Separation of tanks 1 and 2.


Burning GEO transfer core.


Transfer stage burnout.


Separation of payload from GEO transfer core.


Final orbit 1. Additional info in bottom left.


Final orbit 2. Additional info in bottom left.

Flight statistics. That's a super low peak G for a launch lol.

Edited May 23, 2020 by Pds314

[Pds314]

Just confirmed that it can indeed launch and circularize a non-inclined GEO from Xichang, which is 28 degrees from the equator, albeit at kind of an overpowered altitude of 2000 meters (sufficiently overpowered that I need to do my gravity turn earlier or I will put my Apoapsis way too high, like over 300 km). I did however botch a stage so I ended up having my Perigee too low.

 

Sidenote: I wanna try using Xichang as a shuttle landing site / international airport. Those mountains are enormous and right next to the launch site.

Of course, this would mean building a shuttle-like vessel, and obviously the best way to do that is in pure stock + DLC in RSS.

So maybe a side challenge, build a shuttle-like spacecraft that can launch 29 tonnes in its cargo bay into eastward LEO, and 18 tonnes to a >85 degree inclined polar orbit, can maneuver in space, and can land back on a runway.

Edited May 19, 2020 by Pds314

[Pds314]

Alright, successful launch from Xichang launch site, People's Republic of China, in the Bombardier III rocket [Craft Download]. It'll be hard to beat from a raw accuracy standpoint.

Payload: 20000 kg of ore tanks, 80 kg of control equipment. 20080 kg.

Final orbit:
Inclination: 0.0 degrees. Maximum latitude of 0.010034. So inclination is actually 0.010034.
Eccentricity: 0.0000 (actually 0.000014863).
Periapsis: 35,792,356 meters.
Apoapsis: 35,793,420 meters.
Orbital period: 23 hours, 56 minutes, 3 seconds. (I should not have had force on the decoupler! It messed it up by 1 second!)
Longitude of Ascending node: 234.5 degrees.
Arg of Periapsis: 126.3 degrees.
Current Longitude: -76.702, Directly above eastern Ecuador. Nowhere near China...


Actual launch:

Liftoff!

 

Spoiler to reduce page size.

Spoiler

Starting turn a bit early due to Xichang high altitude.


Core stage activate at 15 km.


Boosters unfurling. This is a whole 2 seconds after they decouple. The sepratrons really are just barely enough.


Ascending on liquid fuel only:


We need to angle up to keep our Apogee far enough out.


Shattering the fairing and losing the liquid boosters.


Accelerating on core stage.


Upper stage activated.


Almost in orbit.


In orbit. With 252 Delta-V left in the core stage! This rocket really could put bigger payloads in orbit even than this 87-tonne GEO transferer and test payload ore tanks.


Aiming for what I thought was GEO. I forgot about the non-oblateness of RSS and made the mistake of using Google search to find out what GEO altitude is, so that's why my altitude is the real altitude of GEO sats but still wrong.


Upper stage gives its remaining Delta-V to the transfer.


Transfer vehicle burning from drop tanks 5 and 6.


Separation of drop tanks 5 and 6.


Separation of drop tanks 3 and 4.


Finishing up the transfer burn.


Almost perfectly on-target to but several kilometers short due to aforementioned web search of GEO altitude rather than calculating it for a spherical Earth. a few days ago I abused spherical Kerbin to make a boat that goes toward the equator without power. Now apparently spherical Earth is getting revenge on me by having the wrong sea level vs Oblate Earth.


Separation of drop tanks 1 and 2.


Transfer core finishing up transfer.


I slightly overshoot. Also I'm 0.8 degrees inclined.


Correcting the inclination.


Due to the aforementioned unrealistically spherical Earth, I am at the real correct altitude above equatorial sea level, and within 63 meters of a circular orbit. Unfortunately, I am at 20 seconds too short of an orbit. This was when I realized... I messed up.


Orbital period is now corrected. This took way, way longer than you might expect. You have no idea how long you can take to consume 3 m/s of Delta-V making minute corrections with engine gimbal as your only directional control. Going from 33 m/s of Delta-V after inclination change to 30 after getting this orbit took literally hours.


Decoupled and... apparently I'm now 1 second faster. Why did I keep force% on the decoupler at 100...


New orbit.


More orbital info.


Latitude and Longitude slightly after ascending node.

Analysis of cost, mass and Delta-V:

Nominal Delta-V in editor: 12382 m/s, vacuum, with hypothetical non-release of SRBs until after core burnout.
Delta-V, vacuum, with core stage activation simultanously with SRB burnout: 13580 m/s.
Delta-V, with core stage activation on the pad: 12967 m/s.

Delta-V, experimental, 1 sextillion (10^21) meters or 105702 LY, the width of an entire galaxy, away from the sun, including all decouplers:
Launch vehicle: 9268.0 m/s. (which means my launch to LEO took only 9016 m/s of VACUUM Delta-V!)
Transfer vehicle: 4227.2 m/s.
Whole vehicle experimental DELTA-V: 13495.2 m/s.

Cost excluding final payload, but including fairing and decoupler: 1,342,191 funds.

Mass, excluding final payload, but including fairing and decoupler: 6,001,416 kg

Final payload: 20,080 kg.
Orbital payload: 86570 kg.
Orbital payload + unburned fuel in upper stage: 95790 kg. (this suggests this is more like a 96-tonne class launcher, not 87).

Mass ratio to GEO: 0.333%
Mass ratio to orbit, payload: 1.438%
Mass ratio to orbit, payload +unburned fuel: 1.591%

I'd say overall pretty decent for a pure chemical rocket with no asparagus-style fuel crossfeed.

Edited May 23, 2020 by Pds314

[joshudson]

This idea comes up from time to time. I'm gonna leave this here.

 

[moar ssto]

I haven't seen any stock part rss ssto challange so far, hmm. 

[DunaManiac]

I've actually done something like this before, not for a challenge though. I created a small one person craft and it could reach Earth Orbit, and I actually got a ship to fly past the moon, but the screenshots have been lost to the sands of time.

[moar ssto]

2 minutes ago, DunaManiac said:

I've actually done something like this before, not for a challenge though. I created a small one person craft and it could reach Earth Orbit, and I actually got a ship to fly past the moon, but the screenshots have been lost to the sands of time.

You mean an ssto?

[DunaManiac]

Just now, moar ssto said:

You mean an ssto?

No, not an ssto.

[Pds314]

17 minutes ago, moar ssto said:

You mean an ssto?

Is an SSTO even possible? Maybe some kind of Nerv craft...

[moar ssto]

6 minutes ago, Pds314 said:

Is an SSTO even possible? Maybe some kind of Nerv craft...

Possible if you accept aerodynamic trickery, it uses rapiers and nervs and only uses the open cycle of rapier engines.

[Pds314]

Just now, moar ssto said:

Possible if you accept aerodynamic trickery, it uses rapiers and nervs and only uses the open cycle of rapier engines.

There isn't too much FAR trickery possible though. You can make it sleek, but not delete drag entirely.

Edited May 20, 2020 by Pds314

[moar ssto]

They work in stock aero only, there are tricks you can do in FAR, bu the problem is in FAR, wings have rubbish hypersonic L/D ratio compared to wings in stock aero, so you will end up with far more drag with far, no matter how much magic you do. 

Edited May 20, 2020 by moar ssto

[Pds314]

29 minutes ago, moar ssto said:

They work in stock aero only, there are tricks you can do in FAR, bu the problem is in FAR, wings have rubbish hypersonic L/D ratio compared to wings in stock aero, so you will end up with far more drag with far, no matter how much magic you do. 

Yeah I think you probably want to fly it half way between aircraft and rocket. Use the rapiers and Nervs to loft your Apogee up so that the Nervs can do the work with minimal lift necessary.

[moar ssto]

57 minutes ago, Pds314 said:

Yeah I think you probably want to fly it half way between aircraft and rocket. Use the rapiers and Nervs to loft your Apogee up so that the Nervs can do the work with minimal lift necessary.

No, due the excessive dv requirements, craft will have a horrible TWR when nervs ignite, so they fly like ordinary planes and purely uses lift to maintain altitude. Stock aerodynamics will give you reasonably good L/D ration once passing the transonic regime, so the craft will have enough dv left after taking away aero losses.

Edited May 20, 2020 by moar ssto

[Pds314]

4 hours ago, moar ssto said:

No, due the excessive dv requirements, craft will have a horrible TWR when nervs ignite, so they fly like ordinary planes and purely uses lift to maintain altitude. Stock aerodynamics will give you reasonably good L/D ration once passing the transonic regime, so the craft will have enough dv left after taking away aero losses.

Not in FAR though. Flying on pure aerdynamics at mach 10 would have you lucky to get an L/D of 2, which means climbing or accelerating would require a TWR of >>0.5 for reasonable efficiency. What I'm saying is to put it on a somewhat lofted trajectory using wings to convert 1800 m/s horizontal to 1800 m/s at a 45 degree climb.

Edited May 20, 2020 by Pds314

[moar ssto]

9 hours ago, Pds314 said:

Not in FAR though. Flying on pure aerdynamics at mach 10 would have you lucky to get an L/D of 2, which means climbing or accelerating would require a TWR of >>0.5 for reasonable efficiency. What I'm saying is to put it on a somewhat lofted trajectory using wings to convert 1800 m/s horizontal to 1800 m/s at a 45 degree climb.

Maybe, but you will not reach high speed if you climb at 45degrees, unless you have a superhigh twr, which will result you having a lot less dv to workwith, and you will need a lot of lfo mix in the closed cycle phase, which will eat away your available dv. By the way, stock parts work best with stock physics probably, with far, when making ssto you really want something like smurff to buff your parts since air is helping you a lot less.

Edited May 21, 2020 by moar ssto

[Laie]

FWIW, here's my attempt. I started with a wrapper of Mammoth boosters similar to Pds314 above, then replaced them with SRMs on a whim just to see what happens. What a pleasant surprise! TWR is incredibly high for my standards, I don't usually see heat effects on ascent (in RSS, that is).

Engines used:
1 Nerva
7 Wolfhound
8 Mastodon
12 Clydesdale

Total cost including payload: 668,256 funds
Total mass including payload: 3,103,048 kg
nominal vacuum dV of the booster: 8888m/s

@Pds314: I don't know how to say it diplomatically, but: all those high-res PNGs really add up. Viewing this page currently requires a 100MB download.

[moar ssto]

3 hours ago, Laie said:

FWIW, here's my attempt. I started with a wrapper of Mammoth boosters similar to Pds314 above, then replaced them with SRMs on a whim just to see what happens. What a pleasant surprise! TWR is incredibly high for my standards, I don't usually see heat effects on ascent (in RSS, that is).

Engines used:
1 Nerva
7 Wolfhound
8 Mastodon
12 Clydesdale

Total cost including payload: 668,256 funds
Total mass including payload: 3,103,048 kg
nominal vacuum dV of the booster: 8888m/s

@Pds314: I don't know how to say it diplomatically, but: all those high-res PNGs really add up. Viewing this page currently requires a 100MB download.

Is there any reason for using lfo tanks for the nerv stage?

[Laie]

11 hours ago, moar ssto said:

Is there any reason for using lfo tanks for the nerv stage?

Other than aesthetics? No. They are configured as LF-only, however, so no worries.

[Pds314]

On 5/21/2020 at 8:23 PM, Laie said:

FWIW, here's my attempt. I started with a wrapper of Mammoth boosters similar to Pds314 above, then replaced them with SRMs on a whim just to see what happens. What a pleasant surprise! TWR is incredibly high for my standards, I don't usually see heat effects on ascent (in RSS, that is).

Engines used:
1 Nerva
7 Wolfhound
8 Mastodon
12 Clydesdale

Total cost including payload: 668,256 funds
Total mass including payload: 3,103,048 kg
nominal vacuum dV of the booster: 8888m/s

@Pds314: I don't know how to say it diplomatically, but: all those high-res PNGs really add up. Viewing this page currently requires a 100MB download.

Oh. Sorry. I will put most in a spoiler.

It looks like nukes are pretty effective at reducing the payload demands. Seeing as our rockets have very comparable orbital payload ratios but your upper stage and payload combined are about 46 tonnes and mine was over 86. How much excess fuel did you end up with in LEO in your upper stage? Or did it burn out right as you reached orbit?

 

Edited May 23, 2020 by Pds314

[moar ssto]

13 hours ago, Laie said:

Other than aesthetics? No. They are configured as LF-only, however, so no worries.

Taking away the oxidizer form lfo tanks and just use the lf space will tank hurt mass fraction alot. 

[CFYL]

On 5/20/2020 at 6:35 PM, Pds314 said:

Decoupled and... apparently I'm now 1 second faster. Why did I keep force% on the decoupler at 100...

Well, we still have to push the upper stage away from the payload. Consider tweaking force percent to 0 and attach small SRBs on the upper stage to push it really far.

 

On 5/20/2020 at 6:35 PM, Pds314 said:

with engine gimbal as your only directional control

You are free to add reaction wheels, if you can endure the added mass. Consider putting it on the upper stage.

[Laie]

On 5/23/2020 at 10:12 AM, Pds314 said:

It looks like nukes are pretty effective at reducing the payload demands.

Well, the payload to LEO has been reduced by, what, nearly 50%? It makes sense that I only need half as much rocket.
Note, however, that my Wolfhound upper stage is contributing much more work relative to the rest of the rocket than yours does.

My launch recipe, by the way: dial in a gravity turn that will bring the rocket close to 30° pitch by the time the first stage burns out, then hold approx 25-30° pitch - precise value depends on the original gravity turn being a little lower or higher than desired. Anyway, I usually stick to the same pitch relative to the horizon all the way throughout the second stage, and until time-to-apoapsis eventually starts to increase on the upper. I'm not using FAR, but even in stock RSS the atmosphere is of zero concern beyond 50km. Stock aero makes it necessary to wrap the interstages in fairings, though.

On 5/23/2020 at 10:12 AM, Pds314 said:

How much excess fuel did you end up with in LEO in your upper stage?

Not much. There were a few droplets left, but IIRC they amounted to 50m/s at most. I had planned for the nuke to provide perhaps 100m/s to making orbit, but found that this leaves not enough dV for going to GEO -- not at nuclear TWR. The next model will be a little heavier.

Or maybe it won't. @AllenLi is explicitly allowing Near Future stuff, and I wonder if I should have a look at these fabled VASIMR engines. I'm not familiar with NFT, but browsing the data on github, it seems as if you could get 280kN / 2000 ISP ( or 66kN / 6000 ISP) from a 3t engine, plus however much mass you need to satisfy the power demand. That might already work even as an upper stage.

[CFYL]

2 hours ago, Laie said:

Well, the payload to LEO has been reduced by, what, nearly 50%? It makes sense that I only need half as much rocket.
Note, however, that my Wolfhound upper stage is contributing much more work relative to the rest of the rocket than yours does.

My launch recipe, by the way: dial in a gravity turn that will bring the rocket close to 30° pitch by the time the first stage burns out, then hold approx 25-30° pitch - precise value depends on the original gravity turn being a little lower or higher than desired. Anyway, I usually stick to the same pitch relative to the horizon all the way throughout the second stage, and until time-to-apoapsis eventually starts to increase on the upper. I'm not using FAR, but even in stock RSS the atmosphere is of zero concern beyond 50km. Stock aero makes it necessary to wrap the interstages in fairings, though.

Not much. There were a few droplets left, but IIRC they amounted to 50m/s at most. I had planned for the nuke to provide perhaps 100m/s to making orbit, but found that this leaves not enough dV for going to GEO -- not at nuclear TWR. The next model will be a little heavier.

Or maybe it won't. @AllenLi is explicitly allowing Near Future stuff, and I wonder if I should have a look at these fabled VASIMR engines. I'm not familiar with NFT, but browsing the data on github, it seems as if you could get 280kN / 2000 ISP ( or 66kN / 6000 ISP) from a 3t engine, plus however much mass you need to satisfy the power demand. That might already work even as an upper stage.

It's fine, and I too only viewed their release threads for their propulsion sys and launch vehicles but not downloaded due to its massive size. If all that specific impulse isn't enough, we may need KSPIE, which is over-powered for this challenge, and not allowed. You know, NFT is in the "near future" which we may see, but KSPIE is in the "far future", which we would probably be unable to witness. It is interesting anyways, if wee have some engines giving off burned exhausts at freaking high speeds, like what NFT does. Chemical rockets are nearly to its end of development (in payload capabilities) in real life, but not in KSP. 

I know everyone has different habits, but my gravity turn usually initiates at some 15 seconds after launch, tilting it to 5^o at first, and slowly turn it afterwards, until ap exceeds 200km and 2min, for my low TWR second stage to get enough time to get into orbit.

BTW, boosters don't have to be symmetrical, and Atlas knows why. If 6 isn't enough and 8 is an overkill, just put 7. Don't really have to care about the deviation, if your gimbal is strong enough. CBC-styled rockets like Delta-IV and FH may also be helpful, if your core stage TWR is over 1. My rockets sometimes end up heavier, and more expensive, using more smaller boosters.

Do not explode like N-1. Do not let Jeb poke a hole in your first stage liquid fuel tank. Do not let Bill crash a home-made missile into the engine. Do not try to use f12.