sevenperforce

Give Pluto to Neptune, and fuse Triton with Ganymede to use as the core of a super-earth water planet.

Randal Munroe has some ideas about changing our solar system for the better. Looks like it would make it much more like the Kerbol system.... I can get behind more asteroids.....

I'm sure most of us here have seen, or are familiar, with the Lightcraft -- a design which would use a ground-based laser to accelerate it through the atmosphere and into space. Rather than using photon pressure, as with a lightsail, the lasers would be focused to superheat the air under the craft, causing plasma explosions that accelerate it upward against an aerospike nozzle. Its nose would form an inlet to compress air into the heating zone like a ramjet. There have been several proofs of concept constructed and tested, with decent degrees of success. It's a neat idea. An orbital version would use a huge laser to track the ascending vehicle, which would carry onboard propellant to release into the heating zone as the available atmospheric reaction mass decreased. The vehicle would also carry a small amount of onboard chemical propellant for final orbital insertion once it was out of range (alternately, an orbiting solar-powered laser array could be used in place of the ground-based array once out of range). The idea of a spacecraft rising on a column of light, a sort of bifrost space elevator, is common in science fiction: It got me thinking. Suppose you had a "bifrost bridge" spaceport which could use lightcraft tech to lift payloads to the edge of the atmosphere, but could not effectively turn/focus to send them downrange. Thus, you could cheaply lift virtually any payload to 50-60 km but it would have negligible velocity. Under those circumstances, how would you design an SSTO vehicle to reach orbit? What engines and propellants would you use? How would it return to the surface?

I want to see the completion of Breakthrough Starshot. At my current age we could have close-up images of another star system before I die.

Now THAT looks like flight hardware. These are some cool photos. Looks like the SuperDracos kept firing for a while. One of the things that surprised me in the presser was that the computer uses the SuperDracos for differential thrust at a millisecond-response level during abort. I knew the SuperDracos could use differential thrust for pitch, yaw, and roll during landing, but I didn't realize they could respond quickly enough to be useful in an abort. I was expecting a pure "shuttlecock" scenario, with the fins providing guidance during boost.

Law school is all about class rank, not about absolute grades. However, my school only calculates class rank at the end of the year; the midterm grades are reported as a bloc without being tied to specific people. This means I have the total grade spread from each of my classes, as well as my own personal grades. My guess is that you can create a bell curve that predicts where a given GPA puts a student in terms of class rank; I'm just not sure how. Any ideas?

Yeah they already built it for the first CC flight so.....

Next to a hemispherical section, an ogive cone is surprisingly good at holding pressure. And the whole thing is going to be insulated against re-entry heat anyway. Honestly having propellant right up against the metal is going to provide a heat sink which will be a little better than having nothing behind it. The oxygen tank runs a central column pipe through the methane tank. Oxygen is more dense so this is a good idea; plus having heavy oxygen farther forward helps with aerodynamic stability on ascent.

Following on...

There are just a lot of possible architectures. I wonder how much of a weight penalty it is to use larger, stronger landing legs to accommodate the descent stage.

But why rotten? As "scavenger" I mean any species eating someone's else prey, as I described. Are vultures and jackals scavengers? Do they eat only rotten meat or, as well, just killed or dying? For a scavenger, rotten meat is far more likely meat than fresh, so there will be selection pressure to adapt to a broader range of rotten foods. Natural selection 101. Vultures are not readily able to eat fresh meat. They will eat the eyes and other exposed organ parts from a recent kill, but they have to wait for nature to break it down before the rest of the carcass will become accessible. They have extreme rotten-meat adaptations, from a bald head (to reduce guts getting stuck in feathers) to extremely acidic stomach acid (allowing them to eat anthrax, botulism, and other deadly bacteria with impunity) to colonies of symbiotic bacteria living on their skin (fighting off other bacteria and preventing infection). When we are facultative bipeds, 1 m high, 30 kg heavy, like Lucy? And have only sticks and stones rather than spears? It's 2 mln yeras ago. I'm afraid, the megafauna wouldn't notice our presence. Our investigation of facultative bipeds indicates they were primarily herbivores, eating nuts, roots, and seeds. Not so much meat. The first protohumans to eat meat in any large quantity were likely Homo erectus and their relatives; that's when we see a decrease in gut size and molar size. Without the massive jaws of predators like hyenas and lions, we needed tool use before we could effectively butcher larger animals and break apart bones. Hunting small animals is a low-reward, high-energy activity, and small animals would have been much faster than us and difficult to catch. There may have been a little scavenging at the start, but once we had tools to effectively scavenge megafauna carcasses, we had the tools to hunt.

So....beautiful. I'm not sure on this point. Back when they were talking about Mk1, he either said "we'll eventually make the nosecone the tank" or "the orbital versions will make the nosecone the tank." I don't know which. It's certainly possible that the LOX header tank could be suspended inside the nosecone-turned-methane tank.

One of the saving graces for Starlink, at least presently, is that they are fairly low-altitude. The lower the satellite, the shorter the period that it is illuminated at night.

Not if it is a single stage craft. The Lockheed Martin Mars-Precursor Lunar Lander single stage craft was a dud with respect to payload delivery. The LockMart single-stage LL was not designed to drop off cargo. A stage with engines mounted on each side can drop objects more easily. I am totally here for a crasher-stage lander. Throw the big dV requirements at a balloon tank; make the throttleable, complicated bit the triple-redundant, super-safe part.

And a rhino. He's blind and stupid, but that's not his problem. I love this. I have never agreed so much with utterly useless statements. We can't actually run very fast. We can run very far, though. In a group, with spears, running far rather than fast makes you a better predator than a scavenger. I suspect that if our savanna ancestors had subsided by scavenging, we would be better-adapted to eat rotten crap than we are. As it is we can only eat a small, carefully-curated selection of rotten foods (cheese for example). By the time the vultures circle, the food is kinda wasted. We want the good parts. To a degree. But better to use our ginormous brains to stalk the megafauna, pick off the young, sick, and elderly, and dispatch efficiently. More meat to carry back to our own young, sick, and elderly. Two points. First, a band of noisy apes would not run away from a lion. They would kill a lion. Like I said before, there are no carnivores that can stand up to a band of determined athletic paleolithic dudes with spears. We kick feline butt. Second, if there is still meat on the skeleton, that band of noisy apes is going to strip it clean, because they figured out that drying it will make it last longer and give them a source of protein they can pass on to the rest of the tribe.

A pack of humans is much more dangerous than a pack of wolves. A bunch of dudes in good shape with spears can easily rout a pack of wolves or a pride of lions. An angry herd of elephants is about the only thing that can reliably beat a group of determined pretechnological humans, and they aren't carnivores. We are also bipedal, so we have a massive endurance advantage. We cannot sprint nearly as fast as a wolf, lion, or antelope, but we can jog behind an antelope on the savanna for hours until it drops dead of exhaustion (or at least until it is so exhausted it just stands there and lets us spear it). If there is available game, we can work together and catch it and kill it. So for us, it is the availability of game, not competition with other predators, which is our limiting factor. As a result, our guts never had a need to optimize for digestion of rotten meat, like scavengers.

Yes, it is B1045 from the TESS launch on April 18, 2018. You can just make out the edge of the TESS logo below the NASA logo on top. Another view:

I really like having a short ladder to the surface and what appears to be an airlock. Tons of internal volume for sure. There's only so much that can be relied upon in a render like this, but I do note small tanks tucked between the large ones and the capsule body, which are too small to be oxidizer tanks. Thus they are more likely pressurant tanks, which suggests pressure-feeding and hypergolics. The engines look very bare-bones so this suggests the same thing -- no turbopumps. With eight inline engines you can use differential throttling for all your pitch and yaw needs and use RCS for roll control. Something like this could, if the capsule was removed, drop a LOT of cargo on the lunar surface direct from TLI. It could even loft on a smaller launch vehicle and provide part of the TLI burn itself.

Hypergolics are nice because you can pack them into any old nook or cranny because you don't have to worry about boiloff...yet you can't, because if you're pressure-feeding, you need a spherical tank to minimize weight. If you are volume limited, impulse density of hypergols is 11% higher than kerolox, 34% higher than methalox, and 181% higher than hydrolox.

It has a nice scaffold around it that should allow lateral loading without problems.

From NASA's research on NRHO it should take around 730 m/s to get between NRHO and LLO, and 1,870 m/s to get between LLO and the lunar surface. So a round trip is 5,200. That doesn't count the 430 m/s you need to brake from TLI to the gateway. I discussed minimum crew compartment and structural mass upthread. I think 3 tonnes was a nice roomy solution.

Might make sense if humans had evolved from aquatic apes rather than arboreal and savanna apes. Most objects on land are not well-suited for suction in comparison to opposable thumbs. Wood, grass, fur, dirt, etc. -- most stuff encountered by terrestrial apes is simply not smooth enough to allow for suctioning. Opposable thumbs are where it's at.

Funny exchange on my Medium blog: Reader: Me: Reader: Me: Reader: I found it really funny. Maybe not everyone does, but.......

So do I. Not sure how it gets to space, though.

This looks remarkably similar to what I was proposing a few pages back in the thread. Looks like it could also serve as a bus to drop large cargo directly on the surface. What if it has internal props to get back to Gateway?