sevenperforce

Also on the subject of realism...EVA in orbit was...not really a thing for the LM.

A Progress docked with a Soyuz can manage a circumlunar manned mission, I believe. So that's ready immediately. In that sense they are further ahead than anyone else...though once D2 flies, it can do the same thing in a single launch on Falcon Heavy. But, just like the US, Russia has no crew landing vehicle, much less a way to get it into lunar orbit or down to the lunar surface. So any talk of manned missions to the surface of the moon is nonsense.

I would say Sinosauropteryx, since this was the first obviously-non-avian raptor positively identified as having feathers and thus being a close relative of modern birds, but that doesn't exactly roll off the tongue. I do like T. rex but again, same problem. What about Tyrannosaur? Birds are dinosaurs. Theropods, to be precise. There is no definition of "dinosaur" which does not apply to birds unless you get intentionally arbitrary. Mammals are not hairy amphibians; we are hairy synapsids. Synapsids and amphibians are both tetrapods, but synapsids are not amphibians.

Well, it sounds like you're having trouble with rendezvous, not with docking itself. You can test dock and undock by sending up a two-part ship in one launch and then separating and reattaching, but rendezvous is a horse of a different color. The hardest part of the rendezvous is getting an intercept. If you can get to under about 10 km separation, then you've already done the bulk of the work, and the rest is pretty simple if you know what to do. Here's what you do. Make sure you have targeted your target in the map view. Click the navball velocity indicator until it reads "target". Turn the navball until you are pointing retrograde. Burn until velocity is zero. Turn the navball until you are pointing toward the target indicator. Burn about 10-20 m/s. Wait until you are as close as possible to your target, then repeat steps 3-6. Just keep repeating until you are close enough to initiate docking visually.

Obviously a bug, but fwiw, you can turn off the truss structure itself using advanced tweakables, and sub in struts.

You run into some problems with power management and heat rejection. If the laser is powerful enough to ablate the surface and therefore produce thrust, then it's powerful enough to rupture something and blow it up.

It is very, very tempting to include at least the DLC capsule for the Soyuz spacecraft. But my stock Soyuz is not too bad. So I will probably stick with stock, except perhaps for a few of the payloads themselves. Tweakscale is not fully functional with 1.4 yet, which sucks.

Well, / is the same as ÷, haha. But here, I wrote it all out in as plain of notation as I know how:

Doesn't really roll off the tongue... But then again, neither does Peregrine.

Pretty damn sure I could do that job with about a week of training, too...

Say, I don't think we've discussed this... What's the name of the BFR going to be? It may just stay "BFR" or be something like "BFR Launch System", in which case you might see a line like, "The Heart of Gold, a BFR system spaceship built by SpaceX, lifted off from Mars today for its return trip to Earth." Or it could get an official name, like the Falcon 1, Falcon 9, and Falcon Heavy. The kestrel and the merlin are both species of falcon, though we know Falcon was named for the Millennium Falcon. Based on this nomenclature, "Raptor" would have been a better name for the launch vehicle itself, since raptor is a general name for all birds of prey (the engine could have been named Condor or Eagle or Goshawk or somesuch). Other potential bird-themed names: Osprey Harpy Phoenix Gryphon

I'm really honestly lost as to where the appeal of going with ULA is vs SpaceX, as a commercial customer. Does ULA have less of a backlog? I love this, though: I WANT THAT JOB

The BE-4 is only going to have about 54% of the chamber pressure of the Raptor, so we can expect a much more significant difference between SL isp and vacuum isp than with Raptor. The BE-4 will need a higher expansion ratio to achieve maximum efficiency in its vacuum variant. BE-4 is a single-shaft ORSC engine, so its turbopump assembly will be slightly smaller than Raptor's. But Raptor's much higher SL isp and ridiculous chamber pressure will give it a higher TWR nonetheless. If it edges out the RD-180's isp, it will do so only barely. Another thought, however: Bezos said that was a mixture ratio sweep. The single-shaft turbopump (assuming there are dual transmissions) should be very good for aggressively varying mixture ratio, something that would be a bit more difficult for the higher-performance RD-180 or the higher-still Raptor. So there's a chance the engine can uprate thrust at liftoff and uprate isp further on by pulling an Apollo.

If you have reaction wheels and a reusable tether, you can use rotational deorbiting to boost your antidebris sat.

I have a pretty good fully-stock Dragon 2 in 1.3. Might be able to improve it in 1.4 with DLC.

P.S. Note that in the above example, you can convert the specific impulse of 120 seconds into the exhaust velocity by multiplying with the acceleration of gravity, g0. You get 1,177 m/s, which is about the right exhaust velocity for a hobby rocket motor without a good nozzle.

Specific impulse is easier to calculate for liquid rockets because thrust and fuel flow can be controlled. Solid rockets are not nearly so refined. Just an aside -- are you talking about a commercial solid rocket booster, a hobby/amateur solid rocket motor, or a homemade rocket? If you can assume roughly constant thrust on your rocket, then you can simply take the total propellant and divide by burn time. For example, let's say you have a hobby rocket motor which produces 20 pounds of thrust, weighs 1.1 pounds "full", and weighs 0.1 pounds "empty". Let's say that it takes 6 seconds to burn out. You have one pound of propellant, so your mass flow is 0.167 pounds per second or 0.167 lb/sec. So you take the (constant) thrust of 20 lb, divide this by the mass flow of 0.167 lb/sec, and you get: 20 lb / 0.167 lb/sec = 20 lb * 1 sec / 0.167 lb = 20 sec / 0.167 = 120 seconds If you cannot assume constant thrust on your rocket, then you have to figure out the burn rate and thrust curve. You can do this theoretically if the coring is simple, like a cylinder, but for more complex coring you end up needing some more advanced math. Or you end up just doing it experimentally.

Indeed. Thrust-specific fuel consumption curves arose because airbreathing engines do not run at the same efficiency at all speeds, all throttle settings, and all altitudes. Users of Imperial units found it very natural to look at pounds-per-second of fuel flow when the engine is producing a certain amount of thrust. But dividing fuel consumption by thrust ends up giving you seconds-1, which makes very little sense. However, if you take thrust-specific fuel consumption as constant (invariant with respect to throttle, at least across the test domain), then you can flip your axes and talk about fuel-consumption-specific thrust, which is thrust divided by fuel consumption, which gives you units of seconds. Much easier to work with.

thrust = exhaust velocity * fuel mass flow rate isp = thrust / fuel weight flow rate thus isp = exhaust velocity / acceleration of gravity To be a pedant -- I believe specific impulse came first, as the reciprocal of thrust-specific fuel consumption. "Pounds force divided by pounds per second" is a very straightforward construct.

No, it's 100 tonnes divided by your fuel flow rate. The amount of propellant in your rocket is unrelated; that's the great thing about specific impulse. Specific impulse tells you about the performance of your engine, independent of how big a stage it is attached to. Specific impulse is thrust divided by propellant flow rate. Your propellant flow rate is usually measured in "pounds per second" or "tonnes per second". Suppose your engine burns 1 tonne of propellant every second at full throttle. In that case, fuel flow rate is 1 tonne per second, or 1 tonne/sec. Divide tonnes by tonnes/sec and you get seconds, because the units cancel and the reciprocal flips. You just have to make sure your units cancel properly. If your thrust is measured in kN rather than tonnes, then you need to work in the force of gravity to figure out how many tonnes of thrust you're producing. Are you very good at algebra? Rocket science (at least, at this level) doesn't require calculus, but ya gotta be pretty darn good at algebra.

Exactly.

And vice versa. I'm like, "Oh, right...three point one four one five, uh, nine...ish?" Better than my dad, who has been in the hard sciences much longer and just grunts "twenty-two sevenths!"

To be fair, chutes are just way, way safer.

Obligatory: https://www.smbc-comics.com/?id=1777 Also obligatory: https://www.smbc-comics.com/comic/2012-07-21

I like explaining it to newbies in terms of mass flow because it's more intuitive than momentum impulse and allows an immediate comparison of jets and rockets without having to worry about nonsense like "effective exhaust velocity". He seemed confused by "the axis of the engine" so I thought it best to stick to thrust and mass flow.