sevenperforce

Yeah, this is a promising solution. It's easy enough to set individual wheel motor direction.

Prove me wrong!

They should make bigger landing legs but require an engineer onboard in order to refold them.

I think there's a solution. There are three different use cases for non-physics timewarp; three reasons it is done. The first reason to warp is something we'll call position warp. Position warp is used when you simply want to change where you are in your current orbit, irrespective of any other objects. For example, your shuttle is in LKO and you want to deorbit at the right location so you can make a gliding approach to the KSC runway, so you warp around to some specific point relative to KSC. Or perhaps you're in low Duna orbit and you want to warp around to the preferred injection burn point for a Hohmann transfer to Ike. Position warp is also used on ascent; if I only need 20 m/s to circularize but I'm still 6 minutes away from my apoapse at 100 km, I'm going to warp around to my apoapse, then fire my engines. Finally, position warp can be used if you are trying to rendezvous with another vehicle but need 4 or 5 orbits to pass before you reach closest approach; you can warp around to rendezvous. Position warp can be measured in radians, because you're just changing your position along a fixed orbit. The second reason is what we will call true warp. You've just completed the first leg of your Hohmann transfer to a distant destination, and you don't want to wait hours or days or years to get there, so you warp. The trouble is, it's not the same as position warp, because you're aiming for a destination, and you rather need that destination to be there when you arrive. This is the more challenging use case. The final reason is what we will call dynamics warp. You're waiting for an ideal transfer window, so you jump over to the Tracking Center and wait until the planets align. If you're lazy, like me, you probably already flew your vehicle's ascent, so your poor Kerbal spends three years whipping around Kerbin in LKO while you wait for the perfect moment. In dynamics warp, it doesn't matter where vehicles are located; you're only concerned with where the planets (or moons) are located. To deal properly with warping, you need to handle the use cases differently. Position warp can be dealt with easily, as discussed upthread. Right now, if I want to move to a specific point in my orbit around a single body, I simply click where I want to go, select "Warp Here", and it happens. In multiplayer, the same thing would take place, but instead of warping there, I jump there as if I had used HyperEdit or the debug menu. Nothing else shifts. There is a slight potential for abuse, in that you can jump directly to closest approach with another vehicle instead of waiting for an intercept, making launch windows less important, but that is not an unreasonable tradeoff for multiplayer. There is no free energy; your orbit remains the same before and after the jump, you're just in a different place along that orbit. True warp and dynamics warp are the problem. If you're warping toward a specific destination, moving your vehicle faster along your orbit (as with position warp) doesn't help, because then you'll miss your destination when it arrives. So the solution here is a little more complex. In order to deal with true warp and dynamics warp, each player's warp experience has to be segregated. What is shared across multiplayer is not the entire solar system, but each individual SOI. Suppose Bill wants to go to Duna, but Alice is already on Duna. No problem; Bill does the usual ascent, warp-to-window, trans-Dunian injection, and warp to SOI entry, with all the planet and moon positions stored locally. Once Bill enters Duna's SOI, he suddenly "pops up" on Alice's map view. They share only the SOI, not the whole solar system. This solution does mean that Bill and Alice will see Ike at different locations in its orbit, but that's fine. There may be a moment of confusion if they both do simultaneous trans-Ike injection burns from different points in low Duna orbit, but once they both arrive in Ike's SOI, they share it anyway. I think it can be done.

Upthread, I was discussed a reduced-complexity ISRU system, where the ascent vehicle carries its own hydrazine and merely needs to manufacture LOX to fill tanks which were used for descent. A gallium-phosphide semiconductor, combined with a nickel-based alloyed catalyst, can be used to crack CO2 into CO and O2 using solar power. So all you need is the solar array, a compressor/collector which can work in a 600-Pa atmosphere, and a gas liquefaction system with a small centrifuge. This could be tested in LEO on Dragon 1. Send up the Dragon 1 and have it vent to vacuum. It would have a canister filled with 96% CO2, 2% argon, and 2% N2, attached to a valve. The valve would release gas at such a rate as to maintain a constant internal capsule pressure of 600 Pa, and then the Dragon 1 would use its thrusters to put itself into a steady tumble to simulate Martian gravity. The ISRU system would kick on and test everything. Oxidizer is the majority of the propellant mass of an ascent vehicle, so if you can crack it from the atmosphere, you've cut your starting mass down considerably. You'd need to test it in LEO, then send a small version with a working filtration system to Mars on a Falcon Heavy for testing (this would be a good time for a Mars Sample Return mission), then send a full-scale ascent vehicle for testing, and THEN you can do your flags-and-footprints landing. Yes, but at the same time, you do need as much mission safety and redundancy as possible. The TMI needs to put you on a free-return, so that even if EVERYTHING goes wrong, you can still make it home as long as your life support remains functional and your entry capsule is intact. The orbiter cannot rely on ISRU fuel; it needs to carry enough propellant to brake in and out of low Martian orbit on its own.

As always, pics or it didn't happen. In all seriousness, we need to see what you're working with in order to make an educated guess. My uneducated guess would be that you're working with too much wing surface.

Moar Boosters, but okay.

NASA should pay contractors to design components for a Mars mission, pay SpaceX to launch all the components individually on FH, use the ISS to put it all together, and then do an SLS launch without payload so they can use the EUS for the TLI burn.

Yes, that's what Elon said about an hour after the launch.

Put the panels on the props themselves, if you can. Otherwise no, not really.

If you want a reusable lander, you absolutely need a biconic vehicle...but then you need to execute the flip-stall-drop maneuver, which is pretty damn difficult. And you still have to worry about debris impingement. If you are willing to go expendable, you can use a jettisoned heat shield, but without separate landing engines, you still run the risk of debris damage. A workable solution is an Apollo-style two-stage lander tucked behind a heat shield, with LOX-hydrazine on both stages. Landing engines, which need only provide impulse from drogue-stabilized terminal velocity to touchdown, can be canted out like the Dragon 2's, and plumbed to the LOX tanks on the ascent stage. The descent stage includes an airlock, solar panels, compressor, and associated systems for ISRU. The heat shield is retained until touchdown, to protect the centrally-mounted ascent engine. Probably 20-25 tonnes, and needs to be landed at least several months before ascent. Requires, at minimum, one reusable and one expendable Falcon Heavy to put it on TLI (partially-reusable launch to put the vehicle in LEO, and an IDA-only expendable launch mated in LEO for the TLI). If it can be made to fit in the 5-meter fairing.

Nope.

Neither Dragon nor Dragon 2 are viable Mars descent vehicles.

How hard would it be to test a Mars ISRU system in LEO with a little rotation to simulate Martian gravity?

Agreed. Dragon could be used as the ascent vehicle for the astronauts, and/or for the final Earth re-entry vehicle, but anything else is not going to work. Dragon 2 could be made to work for a lunar mission, but not for Mars. Target orbit rendezvous (separating the landing vehicle from the orbiter) is a no-brainer for lunar missions, due to the dV requirements for powered landing, but Mars is different. The possibility of aerobraking or aerocapture means it's not so simple; if you don't have to bring ANY fuel for Mars capture, a direct ascent approach can mean a lower TLI mass than an Apollo-style architecture. But that means the whole vehicle needs to be in a heat shield, which means orbital assembly is out. A hydrazine/LOX ascent vehicle with LOX ISRU (cracking atmospheric CO2 into CO+O2) would work well enough, but it has to be done at least three times: once in a small-scale test article, once in a full-scale unmanned ascent test, and finally in the real article.

Well, yes. But logistically, it's really too much.

Also, random... If SpaceX really wanted to go all-up on an expendable Falcon Heavy launch for a very large LEO payload, they could conceivably deliver MORE to orbit by losing the upper stage altogether and mating the payload directly to the core interstage. Despite the core's lower ISP, you'd still be looking at 75-90 tonnes of payload.

It's also easy to forget that we landed on the Moon at Apollo 11, not Apollo 1 or Apollo "2". It took five manned missions before the first actual landing. Using Falcon Heavies to assemble Mars vehicles, on the same system, would be a twelve-year ordeal, minimum, just for the first landing. And you'd be looking at 25-30 expendable FH launches.

The first west coast sooty was Iridium-NEXT launch three, of Giant Space Jellyfish fame. I thought that was fishy. No pun intended. First of all, Falcon Heavy cannot presently lift 60+ tonnes to LEO. It is volume-limited and the PAF is mass-limited. The upper stage would need a full redesign. But what I meant, for starters, was using Falcon Heavy to actually send something on the way to Mars. If a fully-expendable Falcon Heavy was used to launch nothing but an International Docking Adapter, it would reach orbit with a nice healthy 97.1 tonnes of propellant remaining (the center core would be 330 m/s short of orbit at MECO, btw). If that upper stage were then to be mated using the IDA system to a Mars-ready stack, it could send up to 21 tonnes on TLI. Not nearly enough for a landing. Rockets are not legos, despite what my Roads to Duna challenge suggested. Assembling a higher-energy transfer stage using Falcon Heavy is really well outside the boundaries of what we are able to do right now. The IDA approach is the closest we can do to orbital assembly at this point. Propellant transfer is right out. Orion was intended to be "Mars-capable" only in the sense that it was supposed to go along as the Earth entry vehicle. Anything Orion can do, Dragon 2 can do, apart from propulsion. More importantly, we have no landing or ascent vehicles. The sticker price for FH assumes booster recovery. Buran looked like the Shuttle more for reasons of necessity than anything else. I suspect the same is true with the Chinese Falcon knockoff.

I've used that a lot, but the actual quoted/advertised/observed vehicle performance is more reliable. SilverBird makes too many assumptions about ascent, especially when we are dealing with altered trajectories for RTLS or ASDS. The only thing that matters to the upper stage is staging velocity. The FH was a sandbag; I don't judge it as very useful for establishing anything, especially since the payload mass is unknown. But those staging velocities are very useful. Helps answer questions about BLEO performance. Awesome!

Does anyone have a table comparing staging velocities for expendable F9 to staging velocities for RTLS F9 and ASDS F9? With that sort of data, I could build a very solid model for F9 performance to almost any destination in any configuration.

Swooping from nose-down to nose-first into a controlled stall, followed by engine ignition and vertical retropropulsive descent, seems like an unnatural act of physics comparable to an STS RTLS abort.

In other news, the next SpaceX launch is only a week away! It will be the last flight of a Block 3 stage (this being the one from August 2017). The first Block 4 reflight will be a month later, in March. It doesn't look like we will get more than a single reflight per booster until Block 5...though I suppose they won't schedule any Block 4 re-reflights until they actually have reflown Block 4s handy. So far, the fastest reflight has been booster 1036, at just under 5 months turnaround, for Iridium launches 2 and 4. No future scheduled reflights have a shorter turnaround time, though this will likely change as Block 4 reflights (and, later, Block 5) become standard. What are the best numbers so far on FH and F9B5 performance in reusable configurations? In the post-launch presser, Elon talked yet again about how FH could do a moon landing in one launch using orbital propellant transfer. I think this is a little dumb; the Falcon 9 upper stage CAN'T do orbital propellant transfer. Not even theoretically. It's not set up for it; the required modifications would mean a complete vehicle redesign. BFS will be designed for orbital prop transfer using the base prop loading system, but that's not something F9 can do, especially given the use of helium as pressurant. However, there are other options. A little fun math: if an end-of-life F9B5 is used to launch ONLY an IDA (mass: 526 kg) mated to the PAF, it would reach orbit with around 25 tonnes of propellant remaining. That's enough to send up to 16 tonnes of payload to TLI, provided the payload can be docked to the IDA in LEO. No new tech or dev required.

Yeah, you want to watch plasma boundary layer flow around the engines. The bells themselves can handle a lot of heating, but the surround machinery will get toasty if you don't do something to redirect the plasma. The NG "sextoweb" will wrap down around the engines so that it produces effectively a blunt-body and plasma will flow around the outside. SpaceX has opted to just reserve a little extra propellant and slow down with an entry burn.

Uh...MSL had a whole heat shield. That's what I mean. NG is supposed to be full-up reusable from the first launch, so they are designing it with extra dry mass for TPS.