sevenperforce

An isolated two-body system comprising nonrigid bodies will always either mutually tidally lock or enter an orbital resonance, given time→∞. But in an n-body system, tidal locking or orbital resonances are not necessarily assured. The amount of torque inducing locking or resonance is often on the order of gravitational perturbations from other bodies.

FYI, will not work in a vacuum.

RP1 is used as the hydraulic for the grid fins; helium is used for extending the legs.

IT IS HAPPENING

WHAT SORCERY IS THIS

Parallel staging is rather challenging with hobby rockets because thrust and burn duration have to be exactly the same, and combustion instabilities usually preclude that. But with water rockets you can make the two boosters 100% identical and verify in advance that they're going to have exactly the same thrust and "burn" length. Probably best to set it up like an Atlas, with the parallel boosters on a jettisonable skirt that simply drops away as soon as the side boosters run out of water. Sustainer in the middle.

That will be the name of a ship, not the name of the vehicle itself.

The 1" sugar candy rockets I built had a TWR of around 10 but only about 5-6 seconds of burn time. Nice red exhaust plume, too. PVC wasn't actually a reactant; the purpose of the PVC was to allow me to use a hand press to pack the plug, propellants, and nozzle. PVC will hold the pressure nicely. I cannot stress this enough, though: do NOT use a metal nozzle or cap with a PVC rocket. You MUST use a substance (like clay) with a lower burst pressure than PVC. Otherwise you stand a very, very good chance of creating a pipe bomb. PVC shrapnel is lethal. Another option is to create your own COPV by wrapping a paper tube in narrow, helical layers of duct tape under tension. If you get it right, that will have enough strength to allow you to pack propellants, and you can use a cast clay nozzle or something even sturdier, since the burst mode of a duct-tape COPV is benign. It will have a better mass ratio than a PVC option. Otherwise you have to melt and cast the rocket candy, which is inherently really dangerous. The alcohol bottle rocket is neat...basically making a liquid fuel-air bomb inside a bottle, and then opening one end. You could do parallel staging easier than you could do serial staging.

Elon should name the BFR the Heisenberg and the BFS the Schrodinger.

Standard disclaimer: I'm not a lawyer, I'm definitely not your lawyer, and if I was a lawyer I wouldn't be posing legal advice on a public forum. That being said: if your rocket engine is strapped down for the duration of the burn, and you have no intention of launching it, then you are pretty much going to be okay. No one is going to care, as long as you don't violate any local noise ordinances. It's basically no different from building a really loud campfire, using ingredients which are just a little suspicious.

....yes. But due to the gravitational gradient of the parent body, the satellite is stretched longitudinally along the axis connecting it to the center of mass. If it's rotating faster than one revolution per orbit, then it rotates out of alignment, and the gradient produces net torque to reduce the rotation rate.

The most likely possibility will be hydraulic launch clamps which reach up and hug the BFR octaweb (heiskaitriakontaweb?); these will have powerful enough hydraulics to be able to move a meter or two in any direction and therefore help guide the BFR down. When they come to rest, the whole vehicle will be fully supported by the pad structure

Was reading a hit piece in the NY Post about how "Elon is a fraud" and they said, "SpaceX is a LITERAL failure to launch. Musk's rockets have crashed, blown up, or exploded so many times that he (inexplicably) made a blooper reel." Now, the question of Elon as a person is outside the scope of this thread......but good lord that's some uncommon stupid.

Then no. Cannae happen. I mean, if you have a ship with TWR > 1 and infinite Isp, then I suppose anything is possible. But there is no closed orbit like that.

I used to build my own rockets out of sugar, stump remover, and PVC. Safe enough as long as you use packed clay rather than metal for the nozzle and endcap. Better isp than black powder and lots of fun.

Not if it was rigid. A spherically symmetric body cannot become tidally locked unless it is subject to deformation.

Not if it was rigid. A spherically symmetric body cannot become tidally locked unless it is subject to deformation.

Okay, I got the Terrier 9 flying Jeb to LKO (from Woomerang) with 340 m/s to spare. Granted, he gets up there with just the Terrier, an Oscar-B, and his command seat......but he's there.

I think I heard this in a Scott Manley vid, but prior to WWII the British Interplanetary Society proposed a whole plan to go to the moon using clustered black powder rockets. They figured that spin-gravity would be needed in transit, so they rigged up a special geared observation mechanism to allow the crew to make accurate star observations while in a rotating cylinder.

Tidal gradients pull harder on the near side of the satellite than on the far side of the satellite, causing the satellite to stretch along the vector pointing toward the primary. If the rotation period is greater than the orbital period, then the rotation will rotate the ellipse out of alignment with that vector, and so those same tidal forces will exert a torque on the ellipse which pushes it back toward alignment. So a perfect, rigid sphere of uniform mass distribution would not become tidally locked, as long as it remains a perfect sphere. If the body is not rigid, however, it will become tidally locked. A spherically asymmetric body like our Moon already has bulges, which both increase the amount of torque (hastening the locking process) and provide a lowest-energy state that dictates the final orientation of the body. A nonrigid perfectly spherical, uniform satellite would eventually become tidally locked but there would be no particular preferential orientation (e.g., no particular region facing toward the primary). The Moon's orientation toward Earth is fixed by its collection of bulges. You cannot do a halo orbit but you can do an effective halo orbit by placing a spacecraft just outside a moon's ROI but at an identical orbital period along its orbital path. You can even throw in some inclination if you want the "halo" oscillation effect. Granted, you're next to the moon rather than behind it, but the result is the same.

I came over just to post this. Friggin' awesome.

Tidal locking can only happen in the first place by slowing the rotation of an orbiting body until its rotational period matches its orbital period. A tidally-locked body, by definition, has a rotational axis (and thus a pole) perpendicular to its orbital plane. Tidal locking should be thought of not as a continual force applied to the satellite by its parent body; it's the end result of tidal forces gradually bleeding off angular momentum until the rotational period and the orbital period match. It's the lowest-energy state for the system. If you smoothed out the Moon's internal structure so there were no bulges whatsoever for Earth's tidal gradient to "lock" onto, it would still retain its current one-month rotational period and would still appear tidally locked. Similarly, if the Earth suddenly disappeared, our moon would continue to orbit the sun in much the same trajectory, with the exact same one-month rotational period. A world which somehow was initially rotating around its star with a rotational axis parallel to its orbital plane (by the way, this sort of thing would be EXCELLENT evidence against a deterministic/naturalistic formation of a solar system) would be subject to the same tidal forces as a star with a rotational axis perpendicular to its orbital plane. However, those forces would produce a torque perpendicular to the rotational axis, rather than producing a "dragging" effect as with a perpendicularly-rotating satellite. This torque would be greatest at periapse and lowest at apoapse, and would induce ever-increasing precession of the axis at each periapse. This precession would tend to pull the rotational axis up out of the orbital plane until it stabilized in a perpendicular state, at which point tidal forces would complete the process of slowing down the rotation to tidally lock.

Let's just pause and consider for a moment that Telstar 19 VANTAGE massed over 7 tonnes...making it the heaviest comsat EVER launched to GTO. Which is dramatically more than F9 v1.1's expendable capacity. Which Block 5 launched with enough margin to recover the booster. EDIT: It's also 1.5 tonnes greater than the quoted maximum recoverable GTO payload on the SpaceX pricing list. Which means the rest of those numbers are probably a bit low, too.

It would precess like hell.

Congrats, you've invented a partially-airbreathing air-augmented rocket.