sevenperforce

...yes, that would be the plan.

Actually, it would be a boostback, prior to re-entry. It wouldn't be enough to reverse downrange velocity and execute RTLS, but it would most likely be enough to lower re-entry speed to something closer to a CRS-8 entry profile.

@Frozen_Heart beat me to it, but yeah, the FH core is built differently. The boosters are identical to the F9FT stage 1s, though. Wasn't trying to add any more rampant speculation; just pointing out that reserving additional propellant for boostback is one of the possible survival modes for the FH core.

They may plan on the FH core to carry a larger reserve propellant budget so it can brake heavily in boostback.

My thought was to do a blended lifting body/ballistic surface so that as long as you come into the atmosphere pitched up, the craft will auto-orient to the maximum-drag blunt-front orientation. Active stabilization on launch.

Once you ionize the CO it will want to recombine. Xenon, like all noble gases, has the handy attribute of not ever forming compounds with anything. If you're willing to play with something as deadly as beryllium hydride, use it to build an SSTO.

Moderate: large enough that immediate action is required to prevent serious injury or death; small enough that you have time to take such action.

"Because I'm all about that mass, 'bout that mass, mass fraction" Another factor that is often overlooked but is perhaps far more important: payload fraction. The ratio of payload to inert stage mass at burnout is the payload fraction, and it determines how much structural margin a given design has. Ideally, your payload should be at least as massive as your inert stage mass at burnout; that way, if you need to add strength or TPS or anything else to your terminal stage, you only lose a few percent of payload for the corresponding percent increase in inert stage mass. Payload fraction, not mass fraction, is typically what kills SSTOs. If your payload is only a tenth of your dry mass, then an unexpected 10% increase in structural weight cuts 90% of your payload. In its fully expendable configuration, the terminal stage of the Falcon 9 boasts not a 1:1 payload fraction, but a 5:1 payload fraction. That's money.

It's not hard to see why. In the FT update, a first stage without payload has roughly 8.8 km/s of dV, while an independent second stage has a whopping 11.3 km/s of dV. SpaceX basically stacked a small SSTO on top of a large SSTO and called it a badass rocket.

How many seconds would the crew have to reach and don protective gear in the event of a moderate breach?

Yeah, I'm gonna have to figure a way to cheat using perspective.

You can always have a nice little label that says "orbits to scale; planets displayed on a scale 10,000 times greater". I'm thinking of doing a receding spiral...something like this: Where perspective makes the spiral look like it is receding into the distance.

Yeah, I love that illustration, but it doesn't fit so well in a single graphic.

So I was trying to come up with a way to graphically represent the scale involved concerning the speed of light. I wanted to make a comparison between that speed (~300,000,000 m/s) and the fastest airbreathing craft in existence (the X-43 at roughly 3300 m/s). It's a pretty large gulf. The simplest approach, I decided, would be to depict the distance traversed by a photon next to the distance traversed by the X-43 in some arbitrary period of time. Trouble is, the ratio is 90,333:1. That's a hard distance to depict in a simple graphic; I don't know of anybody with a screen large enough to display a 90,333 pixel line. However, what about a spiral? If I could create a spiral with an arc length of 90,333 cm, then I could display it next to a 1-cm line. That would be a pretty striking way of depicting the difference. If an arc length of 90,333 cm was impossible, I could make a perceived arc length of 90,333 cm...for example, by depicting a spiral with 500 turns and an outer diameter of 180 cm (as if the diameter is constant but the spiral is receding back into the screen). No idea how I could possibly find a way to render that, though. Any ideas? Or any other ideas of how to depict a scale difference of 90,333:1?

The Winnebago outrunning the supersonic seismic wave... ...or was that 2012?

Do you have any appreciation of the difference between a quantifiable risk and an unquantifiable risk? Geothermal heat is so many orders of magnitude greater than our baseline energy consumption that we cannot even alter the rate of heat transfer. We can only create channels to route the heat through generators as it goes past us. Yes, they were. Because the most massive nuclear accidents in history killed fewer people than coal kills every month. You know that even if you include the casualties of Hiroshima and Nagasaki and Castle Bravo as victims of "nuclear power", nuclear power is STILL safer than any other energy source? Thought experiment: If aliens arrived in Washington DC and offered to give the entire Earth free unlimited energy, with the warning that the flux from their energy source would kill ten humans randomly each day, would you take them up on it?

How do you imagine that any human activity could have a measurable impact on the Earth's magnetic field? Our magnetic field regularly fluxes and reverses on energy scales that dwarf the entire cumulative energy consumption of humanity by orders of magnitude. One nuke in Yellowstone Park wouldn't do a thing. You'd have to dig a massive shaft five miles deep, fill it with water so that it would transfer the shockwave more efficiently, and then lower a several-dozen-megaton nuke to the bottom. But after the dust cleared and all life was extinguished, Earth would continue to spin without any appreciable change in the amount of heat it generates. To be fair, I assume Gaarst was talking about what you can see on an unmarked map of the surface topography... As someone who works in certification and testing, an anecdote about "reducing the level of the stress test" really doesn't mean much to me. Those sorts of things are rather complicated. Nuclear power is simply so much safer than any other energy source that it's stupid.

That sounds quite unpleasant, but it should be noted that this is a problem with poor civil engineering, not with overuse of a resource. Globally, you cannot overuse geothermal. Locally, perhaps, but not globally. Nuclear fuel is not used without thinking. Quite the opposite. It is used sparingly, with a great deal of thought and planning and caution, and it is ignored and maligned without thinking. More education about nuclear power would lead to more use, not less use. One idea I still think would work well would be an inflatable wind tower that is vertical with a helical turbine. A really, really tall one (15+ km) under a combination of compression and tension. The power it generates allows you to electrolyze and pump in hydrogen gas at the base to replace diffusion losses.

Well, you don't have to land on it. You just have to match orbit with it. It does the rest.

Oh, that reminds me: I had a perpetual motion machine driven by buoyancy. Hydrogen or helium balloon that rises into the air, then uses a spring to compress a portion of the lifting gas, causing it to drop. Once on the ground, the compressed gas would be released, storing its energy in the spring, and lifting the balloon back up. I knew that the energy exchange between the spring and the gas could not be 100% efficient, but I figured I could make up the loss by taking energy from the upward and downward motion. Took me forever to figure out that the gas would lose energy pushing against the higher atmospheric pressure at the surface...and that this pressure gradient was the only reason that the balloon moved at all.

"...however slight we might think it is..." Not really an issue of "think". We know how much geothermal energy exists, and its rate of escape into the atmosphere. We can calculate exactly the impact of temporarily diverting a fraction of that energy to power our civilization. It is stupidly below negligible. Avoiding geothermal energy out of fear that we will deplete the Earth's internal heat is orders of magnitude sillier than thinking you can save gas mileage by clipping your fingernails shorter. To the OP: I was full of perpetual motion machines, and their analogues. Magnets held tremendous promise. One was a "magnetic blocker" that blocked magnetic fields to let a ball roll down a slope, generating energy, then slid back out of place to let the magnet pull the ball back up the hill. When I learned that would definitely not work, I decided that I could simply put an electrical motor on one end to push the ball out of range of the magnet...not realizing that force x distance = work. Then there was the simple "generator powering a motor turning a generator" idea. A slightly more refined one, when I was around 13 years old, was an electromagnetic Brownian ratchet to extract energy directly from heat. Violated the second law of thermodynamics but not the first (so I thought). Quite a nice setup, if I do say so myself. When I was 16 I designed a battery-powered jet turbine engine for a motor vehicle that was supposed to run on water via electrolysis. Not a perpetual motion machine in any sense, of course, but still not viable.

No, that's a way to deorbit, not a way to land or to orbit in the first place. Though I suppose you could use it for the latter purpose. Its primary value would be for worlds without enough atmosphere for aerobraking. Assuming you have autonomous asteroid mining or some other way to get a lot of raw materials in space, build a 30+ km platform in LEO with a gigantic coil gun in it. Set up solar panels and some sort of energy storage mechanism (flywheels or supercapacitors). When you want to deorbit your spacecraft, you simply load the spacecraft into one end of the coil gun and fire it retrograde, killing its orbital velocity. Far less propellant needed for the deorbit (or, in the alternative, a much easier shot at lithobraking or other landing methods).

So? If the Falcon Heavy is going to be required to begin with, then why worry about trying to minimize launch mass? It's not like they are going to save money on fuel or something.

Surprisingly, once you run the numbers it turns out that a 50+ km orbital coilgun is actually one of the more reasonable ways to kill orbital velocity, regardless of whether you have an atmosphere or not.

This is the part that I keep coming back to. Development of a dedicated lander is NOT cheap...not even close. If you're starting from scratch? Sure, in theory it is cheaper to develop, build, and test a dedicated Mars lander alone than it is to develop, build, and test a multiplanetary lander capable of dropping payloads on any terrestrial world. No question about it. But if your Earth lander that you ALREADY developed with NASA's money happens to be overengineered enough that it can serve as a passable Martian lander or a moon lander with only moderate modifications, then it is almost certain that those modifications will be vastly cheaper than developing a purpose-built lander for each target world. If SpaceX can do a Mars mission or a moon landing or any other shot by modifying the lander they already have, it makes a lot of sense to prefer that approach over the development of a completely new spacecraft. Would a new spacecraft be more mass-efficient? Probably. Does a 15% mass-efficiency increase justify a 400% increase in development cost? I doubt it.