sevenperforce

Not QUITE the runway but obviously within capability so I'll allow it! You are at the top of the leaderboard.

Wow that is some beautiful engineering.

Yep, def counts!!

Yep, hence boost specifically.

Correct. It does, however, have to have enough fuel to make it back. You can use revert to switch vehicles.

@RCgothic If you gave Crew Dragon an aux prop pack in the trunk with 4-6 Dracos and the same propellant tanks it carries internally, it would increase takeoff mass to 12.97 tonnes and give the whole system 827 m/s of dV. That's assuming 6:1 ratios on the propellant tank system. More than enough to get from NRHO back to Earth but not enough to get there and back again. Triple the prop tanks in the trunk and you get 1,112 m/s of dV, which is enough to go there and back again if launched onto TLI by FH with the center core expended (would require man-rating FH). Tripling the prop tanks in the trunk would make the liftoff mass just shy of 15 tonnes, which is more than FH can throw to TLI with full reuse but easily within margins for side-core reuse.

Yes, it's pretty efficient. An escape tower is wasted mass; using the same propellant for abort as for maneuvering means you can take your LES to orbit for nothing more than the weight of the SuperDracos. Note that this is also what Starliner does, although its liquid-fueled abort and maneuvering system are in its service module so it drops that before re-entry. Disadvantage to both systems is that liquid engines are more complex and fault-prone, and if something goes wrong the crew are trapped with it (for example, the capsule that blew up). The original design had enough propellant to do all on-orbit maneuvers and still execute a powered landing, with chutes for abort or for landing backup. As I noted above, there's more props than we thought. Around 450 m/s of dV. Getting in or out of NRHO on a short transit costs 410 m/s dV. In both cases you do a powered lunar flyby in addition to your entry/exit burn at NRHO. IIRC, they said something during the video stream to the effect that the capsule is able to safely LES even if the booster engine does not shut down. I think the peak loading of the first stage is something like 2.5 gees and the abort pushes 5-6 gees, so plenty of margin.

I just dug a little and came across this, from discussion of the pad abort test: "The instrumented Dragon crew module—whose payload includes a crash test dummy, named 'Buster'—and the unpressurized trunk will be mounted atop a simulated upper segment of the Falcon 9 v1.1 rocket and a steel truss framework, which has been installed directly over the flame trench aperture on SLC-40. The overall weight of the stack will be in excess of 21,000 pounds (9,525 kg), plus around 3,500 pounds (1,590 kg) of propellant." So this actually gives us a better picture of things. They say the payload of the crew module "includes" Buster, and it wouldn't make sense to launch with less payload than a normal flight, so I think we can say that it included enough mass to represent an actual ISS mission. There wasn't anything in the trunk, though. Using these numbers, Dragon 2 ordinarily packs 453 m/s of dV. Enough to return from NRHO but only 43 m/s for repeated rendezvous and docking maneuvers, which obviously is not enough. Beautiful shots.

Other rockets with hydrogen upper stages likely stage at significantly higher velocities than NG, since NG has to re-enter and land.

FHe releases payload closer to orbital velocity than NG, which may have some impact. Also, where are you getting NG with 13 tonnes to TLI? BO's website says NG can send 13 tonnes to GTO. For comparison FHe can send 26.7 tonnes to GTO.

Superdracos are not used for on-orbit propulsion for numerous reasons: Waaaay too much thrust Low isp, underexpanded Cosine losses Cannot be re-fired The Draco thrusters pull from the same tanks as the Superdracos. There are four Dracos around the docking port, under the nosecone, that are used for all major orbital maneuvers since they are the only ones which have no cosine losses. Their isp is 300 s and their combined thrust is 1.4 kN; it takes about ten minutes of continuous burning just to deorbit from the ISS. I am not sure if that 9.5 tonnes empty mass is accurate. That might be mass exclusive of cargo, which would include propellant.

Ecoterrorists have seized control of the island runway and are threatening to launch a cruise missile at the KSC if we do not acquiesce to their demands for a rocket-free Kerbin. Attempts to point out the hypocrisy of opposing rockets with a rocket have thus far been fruitless. Negotiations have broken down, and their attack could be launched at any time. Your mission is to destroy the island runway before they can roll out the missile, thus neutralizing the threat and saving the KSC. Are you up for the challenge? Challenge Rules Launch a mission that bombs the island runway with at least 150 units of ore (this will be your "high explosive") as quickly as you possibly can. Time is measured from launch to impact. For the purposes of this challenge, you may use the "Set Navigation" option to give yourself a target on the navball, but you cannot place any physical vessel at the island runway to use as a hard target. Do not use MechJeb or other piloting aids. No physics-altering part mods. Entries will be placed into one of three categories with individual leaderboards: Aces High, Kold War, and Modern Kombat. Aces High Crewed launch from the SPH and return to land on the KSC runway Can only use propellers (stock or BG) as propulsion No staging, other than dropping the warhead; no broken parts Bomb must be unguided, without propulsion Kold War Uncrewed, vertically-launched missile from VAB (do not aim or rotate toward island using clamps, etc) No more than two propulsion stages (warhead can separate and have independent guidance, but no forward propulsion) Solid-fuel-only on final propulsion stage (RCS for pointing is OK) No more than 75 tonnes liftoff mass Modern Kombat Crewed launch from the SPH, fire a guided missile, and return to land on the KSC runway No staging on main craft other than dropping the missile; no broken parts Main craft may not use solid fuel Missile may be no more than two stages Entries not matching the above rules will be entered into an "anything-goes" overflow category. In addition, you can earn the following ribbons to add to your leaderboard entry and mission badge (note that not all ribbons are possible in combination with all categories): Maverick. Fly either Aces High or Modern Kombat with a second co-pilot. Nike Style. Exceed 20g acceleration during boost. K-35. Instead of landing on the runway when you return, land on one of the KSC helipads. Supercruise. Use only jet engines for propulsion. Extreme Prejudice. Instead of hitting the runway, hit the island control tower. Droning on and on. Fly Aces High or Modern Kombat using no crew and only a Stayputnik (no SAS) on the main vessel. Breezy. Fly your crew in a command seat. 2 Foxtrot. Payload lands on runway intact. No Kill Like Overkill. Include at least 300 units of ore in your warhead. No Warning. Impact at over 343 m/s. Carpetbagger. Hit the runway with at least three separate warheads. Winner in each category is the fastest time to impact. Mission badge (still working): Leaderboard Aces High: @Pds314 1:50, No Kill Like Overkill @mystifeid 1:48 @mystifeid 2:29, No Kill Like Overkill, Carpetbagger @JcoolTheShipbuilder 3:07, No Kill Like Overkill Kold War: @mystifeid 0:51, No Kill Like Overkill, No Warning @ralanboyle 1.07, No Kill Like Overkill, No Warning, Extreme Prejudice @Pds314 1:12, No Kill Like Overkill, No Warning, Extreme Prejudice

Good god that's flinchy in all the best ways

Crew Dragon would need 410 m/s to get from NRHO to earth entry interface. Not sure how much dV it takes for rendezvous and docking, which Crew Dragon would need to do twice...let's say 100 m/s total. If Crew Dragon still carries the same prop load as its pad abort test, then it's 1.4 tonnes. At 300 s isp, that's a maximum wet mass of 8.3 tonnes which I am pretty sure is less than a lunar Crew Dragon. An aux propulsion unit in the trunk would work but it would likely take FH out of the running for direct TLI. Starship can't do the Earth return burn; NASA would want independent abort capability via Dragon at any time. Honestly I don't blame them. This is what Orion was originally designed for during Constellation. It is pretty heavy. Still manageable, BOE, but not trivial.

Maybe. Aiming at a capsule is very different from aiming at the runway. I designed my rocket to have a runway-crossing trajectory and then built in small range adjustments so as to hit the runway. If I was going to aim at a capsule I would need a start from a clean-sheet design that had capability for finer lateral adjustment to the final impact point. Accuracy at present is an ellipse around 30 meters wide and 75 meters in length, due to error induced during explosive decoupling. Actually hitting the runway took a half-dozen attempts. What I could do is place a rover in the center of the runway and then see how close I get. But with the involved error it's just a numbers game.

Thanks! If I put a craft on the runway I would have hit it.

It looks like it will rely on the PPE's SEP.

Dragon 2 absolutely does not have reaction wheels. Reaction wheels are pointless on a craft that large and that mobile. Fractions of a second:

Painted. It needs insulation on the lunar surface. Same as the standard methane-GOX RCS but with bigger nozzles.

I was targeting the runway specifically so putting something on the pad wouldn't have helped. Getting the right angle wasn't as hard as I thought it would be. I was using an extremely lofted trajectory and I turned off angle snap to make fine adjustments. Having SAS on, even just to steady it, was key. That way the SRB thrust vectoring maintained my precise angle until I had a lot of speed built up. Otherwise I would have had more uncontrolled pitchover at ignition, amplifying fine attitude presets.

But not really any more details. Except maybe this idea of using multiple mass-produced refueling elements for the Dynetics lander.

By "unguided" I took @Pds314 to mean that this needs to have no control input from me beyond staging. It does use SAS but it does not deviate from its predetermined settings prior to launch. SRB has extremely specific thrust limiter and fuel quantity to fine-tune ascent. Even things like the rotation of the antennae and the translation of the cubic struts were tweaked by trial and error to get the desired trajectory. The warhead is a set of four radial ore tanks, filled to the brim with plutonium in a classic "pretending-to-be-a-nuke" fashion, with a probe core, battery, and reaction wheel inside underneath a heat shield. Warhead descending, moments before impact:

Being only a very poor rocket scientist myself, I would nonetheless freely speculate that an elliptical coplanar posigrade orbit could be better because it lowers the dV requirements for the transfer, landing, and ascent stages between Orion and the poles. It's not a good spot for LOP-G because it has higher stationkeeping requirements than NRHO, but fine for a mission that only uses Orion.

Hah! This is a great idea right up until you do the math on how much drag is produced when you try to scoop the air. Drag is unavoidable here because you have to actually collect the air and take it back to orbit. Let's say notionally that we have a 5-tonne payload released at 100 km at 3 km/s (which is a hypersonic cargo plane but whatever). Let's say that the dry mass of our orbital nukeship is an impossible 1 tonne and it can push air at 815 s isp. In order to boost that 5 tonnes from 3 km/s to 8 km/s, it will need to burn 5.2 tonnes of propellant. Yet it's also going to need to match velocity in the first place, which means it needs to burn 5.4 tonnes to drop to that speed in the first place. So it needs to carry 10.6 tonnes of propellant per launch. How does one dive and collect 10.6 tonnes of propellant? Here we have a problem. When you dive, the air you're encountering is not moving. Even with no parasitic drag whatsoever (i.e., it magically collects and liquifies 100% of the air molecules it encounters), your 1-tonne vehicle moving at 8 km/s will be moving at just 690 m/s after adding 10.6 tonnes of air. Burning to reach orbit again will leave you with only 3.66 tonnes of propellant. So you make another pass.You collect less air, so now you're moving at 3.2 km/s after topping up your tanks, and your second burn leaves you with 5.4 tonnes of props. Another pass, and another, and another, and so on until your tanks are finally full. And all that, only if you can manage a mass fraction of 1:11 in a vehicle with a freaking nuclear engine...and one, I might add, with sufficient thrust to deliver 7.3 km/s in mere minutes.

I'll give this a shot....