sevenperforce

I could support a system where hitting something over a certain speed causes the Kerbal to take damage and have a countdown to get back into a capsule. The helmet could have a higher impact tolerance than the suit.

*reads first line* You'll want the Lorentz factor. *reads on* *is very, very late to the Lorentz party*

Yeah, but that was predicated on the whole "engine slides in and out" approach, which again would require a complete redesign and would fail to validate FH.

This is the biggie. The shuttle/taxi has nearly all the requirements of the cycler itself. And if you must have gravity, just make your shuttle/taxi a tumbling pigeon and call it a day. The only thing Cyclers are good for is ensuring a commitment to extended Mars missions.

That would be a completely new engine. The Merlin combustion chamber cannot be modified to accept an aerospike nozzle. The best they could do would be swap out the Merlin turbopump and build an entirely new multichamber aerospike engine. But even that would be suboptimal. The Merlin's turbopump is designed for high chamber pressure; aerospikes typically use lower chamber pressure. Mount a pair of the new titanium grid fins on either side of the tail of the stage, bolt PICA-X tiles around the perimeter of the payload adapter (the edge of a re-entry surface takes the highest heating, since stagnation pressure protects the center), add a steerable chute, and hope for the best. Maybe aim it at a bouncy castle. Or just do like the early Falcon 9 recovery attempts and just do a controlled splashdown. Probably because there’s no way a 0.3mm (I think) thick nozzle would survive reentry and a restart facing downwards... Also, speaking of which, a Merlin would still produce thrust without a nozzle extension, right? It wouldn’t be efficient at all, but it would work, more or less. So theoretically, they could detach the nozzle extension or let it break apart and then fire the bare engine to land...? Its a bit far-fetched though, I do realize. Even underexpanded, without the nozzle extension, the Merlin would have WAY too high a TWR at minimum throttle on an empty stage to do a survivable suicide burn. And jettisoning the nozzle extension would require a total redesign, which would defeat the purpose of certifying Falcon Heavy in the first place. Allowing it to break apart wouldn't work, either; the shrapnel would shred the rest of the stage, and even if it didn't, any asymmetry in the breakaway would result in asymmetric thrust which would wreck the whole landing. Plus, the deep throttling of the Merlin Vacuum likely depends on maintaining outlet pressure, which wouldn't be possible without the nozzle extension. Flow separation in the full nozzle at sea level would be so catastrophic that the thrust would be completely uncontrollable and would probably rip the nozzle apart.

Not sure if you were referencing my preferred architecture or not, but if you read closely, I definitely have the hab on the return trip. The whole system is fully-reusable and cyclic.

Correct. It would not be simple. It would, in fact, be prohibitively-not-simple. Propulsive landings on the Merlin 1D Vacuum are a non-starter, 100%.

Note that although NG's base diameter is 7 meters, its initial fairing looks like it will be 5 meters. The 7-meter NG will be the three-stage variant, which will probably fly later. I would love to see a 5-meter mini-Raptor upper stage for the Falcon 9 and Falcon Heavy, potentially with an enlarged reusable cargo bay, but without cross-plumbing it simply won't happen.

That's what I thought too, initially, but I have it on good authority from someone in Cape Canaveral (and I don't mean a tourist) that SpaceX absolutely will not cross-plumb its F9 or FH launch pads. The contract with the Air Force was to obtain funding to develop an alternative-fuel upper-stage engine that COULD be used on F9. There was no obligation to actually test or deploy it. All the F9 upper stage really needs is a heat shield, something to stabilize it during re-entry, and chutes, and it can splash down and float, which is technically "recovery". That's what I suspect Elon is thinking of when he talks about setting up the FH inaugural launch for reuse.

The advantage of aerobraking cannot be understated. In particular, since the required dV for the outgoing trip is much higher than the dV for the homeward journey, aerobraking can be used in unconventional ways. My preferred mission architecture for long-term Mars exploration uses a combination of propellant transfer, aggressive aerobraking, reusable shuttles at both ends, and partial ISRU. The core is a ship similar to an Aldrin Cycler, with power and habitation but only small propulsion systems. The main difference is that the whole thing a) carries extra propellant tanks, and b) is structured such that it can point in a single direction and successfully, repeatedly aerocapture at both Earth and at Mars. The cycler is assembled in low earth orbit, and Earth-based shuttles (presumably the second stage of a beefy two-stage launch vehicle like New Glenn or ITSy) gradually fill the ship's propellant tanks, then re-enter for reuse. The cycler carries substantially more fuel tankage than oxidizer tankage. The final shuttle takes the crew/passengers up, docks with the cycler, then uses the fuel that has already been placed in orbit (along with its own engines) to execute 95% of the transfer burn to Mars. Immediately after a Mars intercept is reached, the shuttle decouples, flips to retrograde, and uses a short burst of fuel to bring itself back to an eccentric Earth orbit, from which it can aerobrake in multiple passes back down to a safe re-entry. The cycler uses its smaller engines to complete the transfer burn and make any necessary midcourse corrections. It aerocaptures at Mars, circularizes, then executes a rendezvous with the already-orbiting Mars-side shuttle. The crew transfers to the Martian shuttle and the cycler transfers all its oxidizer and a large portion of its liquid fuel, and then undocks. The Martian shuttle heads for the settlement or research station on the Martian surface. Once on the surface, the Martian shuttle deploys a solar array and begins cracking Martian atmosphere (CO2) into liquid oxygen. This can be done without the need for any drills, reprocessing, or access to Martian ice reservoirs. At the conclusion of a given mission, when the Martian shuttle's LOX tanks are full, it returns to Martian orbit using all but the last of its fuel reserves, and does a rendezvous with the waiting orbital station. The orbiter takes on a small amount of LOX and transfers most of its remaining liquid fuel to the shuttle, which uses its engines to execute 95% of the transfer burn back to Earth. Like its counterpart at Earth, it then flips, burns retrograde into eccentric Martian orbit, and uses aerobraking to return to a low Martian orbit, ready for the next mission. The orbiter aerocaptures at Earth, circularizes, and meets up with a waiting shuttle. Contrary to common assumption, the biggest dose of background radiation in space is omnidirectional. Blocking the sun only protects from high, sudden doses due to unanticipated solar flares/storms; it doesn't protect from the majority of the radiation. Cylers are not-so-useful for the same reason that you can't just "hitch a ride on a comet".

Very, very carefully. Duct tape is probably out. Honestly, though, I would look into a tongue-and-groove arrangement (where the edge of the nozzle slides into the combustion chamber) with retaining/tensioning bolts on the outside. Probably the simplest, most reliable way of doing it.

LOL, sorry if I was too snarky.

I could see that as a good thing. Agreed. Um. Okay, but.... Ugh, noooooo.

Note that in all fertilizations, the ovum is penetrated by many, many separate sperm, but only one reaches the nucleus to fuse.

The benefit of aerocapture at Mars (and at Earth) is substantial. In order to use aerocapture, the crew vehicle would have to break away from the Cycler well before the flyby (on both ends) in order to gently modify its trajectory for atmospheric intercept. However, this means the crew vehicle would have to have extended on-orbit life support compared to a shorter-persistence shuttle intended to ferry the crew from an orbiting mothership. This additional requirement somewhat obviates the value of the high-velocity Cycler, since you have to duplicate life support systems and crew space. Then there's the problem of getting back to the Cycler from Mars. Surface ISRU and a reusable crew shuttle is definitely the best option. Supplies and surface hardware would still all have to be sent via conventional Hohmann transfer to aerocapture in unmanned vehicle. One of the advantages of a persistent orbital mothership is that you can put not only life support and crew/cargo space on it, but you can also put your heavy transfer engines on it, to boost the mass of your actual cargo and crew up to speed for the transfer. But you can't do that here. Yes, an Aldrin Cycler is a space station orbiting the Sun in such a way that it maintains periodic flybys of both Mars and Earth on a repeating pattern, using gravity assists each time.

When is Elon giving his speech on mini-ITS, again?

Sending bulk material, yeah. Or being able to convert ore into bulk material. There could be some stuff you could build from refined ore onsite (tanks, structural elements, etc.) and some stuff (like engines, instruments, etc.) that you'd have to send from Kerbin, but once you send them you can use them to assemble. Career mode could have a whole tech tree for what you and can't build offsite. Heck, even just being able to ship the parts themselves in a standard, compact cargo bay and reassemble them at an offworld VAB, then deploy them, would do wonders. You could build so much.

I play almost exclusively in sandbox, and even I would absolutely love the ability to build offworld VABs and launch pads. It's like ISRU; just because I CAN ship as much fuel as I want directly from Kerbin in sandbox mode doesn't mean I don't like using ISRU when applicable. Building offworld would be similar in that it would allow more flexibility and give even sandbox players the ability to greatly enrich their exploration and mission experience. Not to mention that you could also do this on Kerbin -- build a second VAB and launchpad at one of the poles, for example. Of course the potential for enriched career mode play is huge. Instead of just grinding contracts for money endlessly, players could choose to invest in a Minmus VAB in order to launch more payload for cheaper. To complete a tourist trip to Val, for example, you could build a fairly small crew vehicle on Kerbin, launch it into LKO, and then build your transfer and return vehicle on Minmus without the huge added price of building a ginormous launcher to get it off the ground.

Oops, meant nitrous oxide. Stupid me.

A stock update or mod for Faux Lagrange Points would be helpful. For each moon (Gilly, Mun, Minmus, Ike, and the moons of Jool), define spherical regions of space at L1-5 with a radius roughly 10% that of the body itself, slightly outside the patched-conic SOI of that body. You could also do them for each planet relative to Kerbol. Ships carrying an active Gravioli Detector will see these regions appear on their maps as little spiral symbols, similar to how asteroids look, which can then be targeted. If you enter that region and drop your target-relative velocity lower than some predetermined value (e.g., 50 m/s), you will remain in that region indefinitely, drifting randomly but never actually leaving. Subsequent ships can target that particular ship without having to have a Gravioli Detector and dock with it accordingly. Captured asteroids can also be brought into these regions like spacecraft. This allows for orbital assembly at a predetermined, regular point without needing to enter into orbit around a particular body (e.g., the Mun) or match orbits with another spacecraft. I have been building a copy of the Deep Space Gateway and Deep Space Transport in polar Mun orbit for the Orion Style challenge and it is painful (and dV-expensive) to rendezvous every time after hitting Mun orbit. Like patched conics does for n-body, this mimics the function of Lagrange points without being computationally expensive or hard to understand. It wouldn't cause any change in normal gameplay but could allow advanced and beginner players alike more freedom in orbital construction.

If you're throwing something as heavy as a submarine into space, better break out the pig iron and plutonium. And while FH/NG would be able to handle most of the components of the fission fragment rocket stack, they might balk at the 110-tonne main engine assembly.

Have they even shown proof-of-concept of a dusty plasma reactor?

Do you mean to pump in compressed air? I would look at NO2 or H2O2 if I were you. How are you going to pump in the fuel?

Not an attorney and this is not legal advice... ...but you should check your local ordinances. State law probably won't have any issues, as long as you aren't flying the engine or profiting off of the engine in some way, but your local (city, county, etc.) ordinances may have rules about fires and noise restrictions that you will need to stay aware of.

Overlays are HUGELY important for telling me how my vehicle is handling and whether the re-entry characteristics are within acceptable limits. That being said, I would love to see expansion into colonization and bases that's more than what is currently available. The ability to build offworld VABs, for example.