sevenperforce

Per Wikipedia, they only have two landing zones at present but they have plans for two more. Originally they planned for a total of six landing pads but this has scaled back to four. I want to see Dragon 2 launched on a Falcon 9 RTLS and an auxiliary service module launched a few hours later on a Falcon Heavy, docked in LEO, and sent into lunar orbit.

That article you linked is over a year old. SpaceX has abandoned propulsive landing for Dragon 2 and they have already built a second landing pad (Falcon Heavy, remember?), and possibly a third.

ISS There is a crewed Soyuz launch coming up at the end of this month, and...well, they need somewhere to go, don't they? Obviously I didn't replicate every launch individually, but I did build the ISS in its current configuration and drop it into orbit in one shot. I still need to add the Progress and Soyuz capsules currently docked, but that's a job for another time.

At the Cape?

And let's not forget rocket after rocket, echoing triple sonic booms as they plummet from the heavens to touch down on tongues of fire. I know it's unlikely, but I'm very much hoping we'll one day hear Elon say, "We're gonna need another landing pad."

A common point of confusion: increasing the chamber pressure does not increase specific impulse without limitation; otherwise you could get ridiculously high isp just by amping up pressure. Rather, it increases the specific impulse for a given expansion ratio. Chemical propellants have a certain amount of chemical potential energy. Igniting them in the combustion chamber converts this chemical energy into thermal energy with very high efficiency. However, converting that thermal energy into controlled thrust (kinetic energy) is the hard part. The more your exhaust flow expands, the more of its thermal energy is converted into kinetic energy. An engine with a chamber pressure of 2 atmospheres can have 50% of its thermal energy converted by expanding to 1 atmosphere or 100% converted by expanding to vacuum. An engine with a chamber pressure of 10 atmospheres can have 90% of its thermal energy converted by expanding to 1 atmosphere or 100% converted by expanding to vacuum. The SpaceX Raptor engine has a chamber pressure of 247 atmospheres, so it can have 99.6% of its thermal energy converted to thrust by expanding to 1 atmosphere. Of course there are always other efficiency losses; these percentages are the theoretical maximum. But it means overall that for a generally higher chamber pressure, you can utilize more of the total energy at sea level, and you can use more of the total energy with a smaller engine nozzle.

I've always loved the way the Soyuz launch looks. Originally I was going to have them open up with Separatrons but a counterweight was just as easy.

One other highlight, because I can't resist:

Mission post: Highlight:

O3b, Arianespace with Soyuz-FG

It was delayed.

Just re-flew this launch with seconds to spare. About to put it up here: She's off!

12:10 EST.

So you're thinking the first burn for orbital insertion, the second and third burns to raise apogee, and the fourth burn to change the argument of periapsis for the second pair of sats?

Live launch coverage placeholder shows an Ariane 5, rather than a Soyuz, which threw me for a loop. I already flew this mission once, but I'm tempted to delete the constellation I already have up, fix the core design (It doesn't taper properly) and the cantilever arms (they are separatron-actuated rather than proper counterweight-cantilever), and fly it again. From an article earlier this week: The orbit is five times faster than GEO, which I matched in my first run by placing the O3b sats in a 746.081-km equatorial circular orbit. But does anyone know why the Fregat will fire four times? I'm guessing the first is orbital insertion/circularization, the second raises the apogee to the target orbit, and the third circularizes...but what direction would it fire the fourth time before the second pair deployment?

The course of true love never did run smooth.

One of the fun things about reactionless drives is that you can ask their inventor to explain how, exactly, net thrust is produced in their desired direction, rather than in the opposite direction.

Expansion ratio. A larger nozzle allows the exhaust gases more opportunity to expand against the nozzle to produce thrust. More thrust for a given amount of propellant = more efficient. So, the question is: why don't all engines have ginormous nozzles? The first reason is pressure. The more the exhaust gases expand, the lower their pressure drops. If an engine is firing inside the atmosphere, and its exhaust gas drops below atmospheric pressure, then air pressure is going to start to flow into the nozzle around the lip. This decreases thrust and efficiency and can even cause catastrophic damage if the exhaust flow becomes too uneven and exerts asymmetric pressure on the nozzle. The other reason is weight. Making your exhaust nozzle twice as big may only increase your thrust and efficiency by a few percent. It's worth it for an upper-stage engine, where weight isn't as much of an issue and efficiency is vital, but for atmospheric engines you don't want the engine to be too large or too heavy because you need high thrust and low weight to get off the ground quickly.

It's even simpler than that, actually. The net forward momentum that the assembly has from a single cycle is exactly equal to the net rearward momentum that the spring-bound weight has.

Yep. Thrust-specific fuel consumption is fuel flow rate divided by thrust. If you use the weight of your fuel flow, as is typical in the airline industry (e.g., "pounds per second"), then you have weight per time, divided by thrust. But weight and thrust are both units of force, so they cancel, and you're left with seconds-1. Take the reciprocal, and you get the specific impulse, measured in seconds. If you use the mass of your fuel, then force does not cancel and taking the reciprocal gives you a speed in m/s. Isn't dimensional analysis great?

The exhaust velocity is finite; the effective exhaust velocity (and corresponding isp) is infinite. In comparing airbreathing impulse engines to conventional rocket engines, the actual exhaust velocity is useless since you're using air as reaction mass. So effective exhaust velocity is calculated as the reciprocal of thrust-specific fuel consumption, because thrust-specific fuel consumption can be used to make direct comparison between airbreathers and rockets. The fuel consumption of an electric ramjet is zero, so thrust-specific fuel consumption is zero (assuming net-positive thrust), and the reciprocal of zero is infinity. So, yes, specific impulse is infinite, even if the actual exhaust velocity is finite.

The great thing about this engine is you can place it anywhere on your craft, pointed in any direction, and you'll still end up producing the same amount of thrust.

Fun fact: a long, long time ago, some guy proposed mounting a machine gun with a steel plate above it, and firing continuously so that the impact of the bullets would force the plate upward. The bullets were supposed to fall back down and be re-collected for reloading. He, of course, forgot that the recoil of the machine gun would counteract any thrust gains. But it didn't keep him from selling tickets to fly to the moon.

This is so many kinds of fantastic.

ISS question, since this is the NASA thread... I've started a save where I'm building and playing through every orbital launch worldwide: So far I've done an Atlas V, a Falcon 9, and a Soyuz-FG (though it's not due to upload until Friday). But we will have a Soyuz flight to the ISS later this month, so I need to put an ISS clone into orbit so it has a destination. I'm having trouble finding sufficiently detailed ISS schematics to actually build an ISS clone in the spaceplane hangar (though I'll be putting it into orbit with F12). Any tips? How would you design an ISS clone in KSP? The only mod I'm using is Tweakscale.