sgt_flyer

For the disparity between proton and other rockets, keep in mind at which point the proton second stage is ignited - waaay earlier during ascent, because proton is a full 3 stage serial rocket + an additional transfer stage most of the time. (block D for proton K, briz-M for proton M)

For the lem, it's RCS fuel tanks used bladders, but the main pressure fed engines fuel tanks did not. (Bladders are not easily upscalable) They used their RCS as ullage to settle the fuel in the main tanks before sending the helium.

I think piezoelectric roads might be more interesting (at least in zones with a lot of traffic, like cities) Converting traffic generated vibrations into electricity

It seems that such cases occurs, but the embryo is generally not viable. (One of the only documented cases (in 2007) where the embryos survived had seen the egg split to create twins. Although those twins are stated as 'chimeras' where some of the organs of one can end up in the other body.

One of the problems, is the payload costs a lot - the launcher's price is only a small part of the price tag for a full launch, without even accounting for all that happens around : calculating ascent path / final orbit, if there's going to need to move other satellites, and the launch installations and crews running costs. Add to that the pricey insurances for the payload In the end, a reusable system might lower a bit the full price - after a while. At first, launch safety / insurances will cost a lot more for an unproven system, and they're going to have an hard time finding customers who might be willing to pay for a more expensive launcher with reliability records. If they don't have enough flights per year, a reusable systems running / maintenance costs might offset the gains you have from reusability.

I know about aerospikes - but they are only prototypes. They have been never used on a complete rocket for the moment be it toroidal or linear - only test firings have been made Mainly i think, because they are too costly to develop for expandable rockets:)

Kerolox has not enough isp for a usable SSTO. And the concept you propose already exists and has been researched: http://en.m.wikipedia.org/wiki/VentureStar It faced several problems, notably the demonstrator's multilobe fuel tanks . Ultimately - the budget for it got axed and the project was cancelled in 2001. At this time, the x-33 suborbital demonstrator was 85% complete. Basically, you need a very high isp, at all altitude, and a dry mass as low as possible to be able to take a reasonable payload. a bell nozzle is designed with specific shapes if you want to use it at sea level or in near vacuum - using a nozzle designed for vacuum at sea level will lower your isp at these altitude.

well, after reading their last infos, it seems the probe's actual position if off by less than 30000km than projections made from the last known orbit - in 1986 ! speak about precision orbit -with the updated orbital infos, it seems they'll only need a 5.8m/s delta-v change for making their manoeuver - if they do it on june 17th ! they'll need to be working overtime here to check all the necessary systems before a manoeuver change (plus, they only have limited windows to communicate with the probe + getting a go from nasa - to be sure they won't fry another probe with their amplifier )

i don't even know if they are going to use the superdracos outside of atmosphere - they might only use the normal dracos for manoeuvers in vacuum (as they have a vacuum nozzle - the superdracos don't have one - so i expect a significantly lower ISP in vacuum )

for the soyuz rocket, remember the existence of the rapiers engines, with locked gimbals and in rocket mode - you can also add the 24-77s as verniers for the first stages, and the smaller LV1-R's for the upper stage verniers the rapiers make for nice looking 4 nozzles engines in 1.25m

Well, virgin has already ties with the dreamchaser's company, SNC. It's SNC who is making virgin's spacecraft hybrid rocket engine (liquid / solid) In the end, it gives SNC a low cost high altitude test platform for their hybrid engines (they plan to have twin hybrid engines on the dreamchaser)

It seems someones has been able to reproduce the dragon v2 UI. https://s3.amazonaws.com/pushbullet-uploads/udqSJ-BHDliy8kJw7iA8oo1QKBEBpmBunvtAUY/dragon%202%20ui%20screen%20rev1.png Given that the dracos / superdracos will be used to perform orbital manoeuvers and deorbit / propulsive landings, it should even be able to make a propulsive landing after an abort. I'm really starting to wonder how much delta-v the capsule will have. (Besides, i think they will only use the fuel tanks that are inside the spacecraft - as they'll be able to reuse them, that allows them to use pricey lightweight & resilient alloys for them, which would not be considered for non reusable spacecrafts.

i think you'll need at least 4 long march 5's (and maybe even 5 long march 5 rockets) to get a manned mission to the moon. + a shenzou launch. 50tons to LEO won't be enough by far to get to the moon the N-1 was planned to have 93tons of payload to LEO, Saturn V had 120 tons to LEO. the moon is very far from earth compared to mün from kerbin you need around 4000 m/s of delta-V to get to a low lunar orbit, + around 2000 m/s of delta-v to land, and the same to get back up. then a few delta-v to get back to earth with an aerobrake return. also, the shenzhou would need to have an additional transfer stage to come back from the moon. (you'll need roughly 700m/s of delta-v to get back from the moon, shenzhou only have 380m/s of delta-v. you'll have a 8 tons shenzhou + it's return transfer stage, a very heavy lander (a two man lander like apollo's LEM weights 15 tons) - so you're already looking at something of at least 28 tons to get to the moon, not counting the stage used to brake into low lunar orbit. (assuming they use a Fregat analog stage to get the needed transfer delta-v back from the moon - around 5t)

as always, the main problem with all these technologies, is providing the electric energy needed to sustain or contain the reactions we need better power sources !

by watching the video, - musk said that the superdracos are 3d printed - that's maybe even more interesting to see how reliable they are than the propulsive landing

@blue - which decoupler ? The 3.75m or the 2.5m ? :)the 3.75m one is bugged - it's not flagged as a 'physics' part - creating all sorts of weird behaviour if you try to decouple it. If you simply want to have engines hidden in the upper 3.75m to 2.5m adapter, for clipped engines the most important point is to not have any additional part below the emission point. (You can have working engines fully inside a fuel tank - they'll work unless there are additional parts below the thrust point) - your 'thrust can only go from the inside to the outside of a collision mesh - never from the outside to the inside of a collision mesh The thrust emmission point is usually located around the nozzle's articulation point.

The UR-700 and UR-900 russian rocket concepts - http://www.astronautix.com/lvs/ur700.htm http://www.astronautix.com/lvs/ur900.htm It had it all - pankake build and fuel crossfeed:p (and Moar boosters for UR-900 ^^)

Actually, the rocket being able to do corrections might be useful - especially when crossing such things as the jet stream - the air speed - especially on a lightweight rocket - could easily throw it off course.

one of the question would be - if we end the usage of fossil fuels - is there already something that could replace the plastics we use everyday ? (note, using plants for that can be a problem - you'll need to both grow vegetables / wheat etc and the plants needed to create plastics replacements - unless you'll be able to use leftovers from food production.

Glided landings are useful for pinpoint landings (an apollo capsule usually splashed within a circle of a few km after reentry) - whereas a spaceplane will be able to land easily on a runway. - they are also much more gentle on the astronauts bodies / experiments (both during reentry and landing - less G forces)

It's a possibility, but you'll have to ensure that all of the connection points burn / separate at the same time. (Else your system might risk to pivot around the last remaining connection point (+ the thrust of the upper stage) fully destabilising the rocket

Well, for decoupling, most mechanical latches systems are simply too heavy / not reliable enough. So you'll need to be able to use explosive bolts - which uses pyrotechnic stuff, which are regulated almost everywhere.

If we are to switch away from petrol based resources, we'll need at least energy sources as cheap, high density and reliable than what we have with petrol. (Try miniaturizing a nuclear reactor for your car ) As most of those energy sources would be first too bulky to get into everyday life, we'll need high density cheap energy storage (aluminium - air or lithium - air batteries comes to mind) With those storage systems into everyday systems, you could even use that to regulate peak energy demands / or even out power from renewable energy sources such as solar / wind / tides. (Ex : a city has renewable energy generators, with only electric cars. While plugged in, those electric cars would act as a gigantic battery to support peak demands / even out shortcomings from the renewable sources)

well, here they talk about the probe, giving it fuel and oxydizer - so it's using bipropellant hypergolics for it's 24 engines (which are most likely the probe's RCS system - could be used for both attitude and propulsion) - of course, not all 24 fire at the same time it has 1670 kg of fuel + oxidizer on board. (i guess they went with the higher ISP a bipropellant gives them over monopropellant, for the mission delta-v requirements) http://www.esa.int/Our_Activities/Space_Science/Rosetta/The_Rosetta_orbiter afterwards, Astrium designed the spacecraft bus - so they might be using technologies they know about - they used MMH and N2O4 on Ariane 5 EPS pressure fed upperstage. (the space shuttle OMS used roughly the same fuels - it had 316 ISP - so we're surely with very near values - Ariane 5 EPS engine had a ISP of 324 - max ISP for MMH/N2O4 is 336)