Recent comments in /f/space

Shrike99 t1_j6js9tu wrote

Reply to comment by iheartbbq in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

You seem to be ignoring the minor fact that lower molar mass also means more moles, so it cancels out.

If you pump 1kg of water into the engine, that's 55.5 moles. If you pump 1kg of hydrogen into the engine, that's 500 moles.

So hydrogen produces 1/9th as much force per mole, but it also has 9 times as many moles per kg of fuel. The end result is that both produce the same total force when that kilogram is expelled from the engine.

Or at least, they would if they were both expelled at the same speed. Since hydrogen actually comes out twice as fast, it produces 1/4.5th as much force per mole, while still having 9 times as many moles, and hence produces twice as much total force.

4

space-ModTeam t1_j6jq0w6 wrote

Reply to Ellon Musk x Mars by [deleted]

Hello u/mrterios, your submission "Ellon Musk x Mars" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

1

scarletperson t1_j6jpc2q wrote

Reply to Anyone very travelled to a rocket launch. by sddk1

Live in Michigan, traveled to Artemis 1 twice. First time in august we got scrubbed twice. We tried planning again in September (the 27th launch date was my birthday!) and got shut down by the hurricane. They finally agreed to go in November so we flew back down and after an hour or so of delays it went off at like 1:42AM. We had passes with KSC to go out to the Saturn V center and we had also brought a nice canon camera for this launch. I do not recommend the traveling experience and if you’re gonna go that far, you have to be ready to do whatever. KSC does not do refunds for the launch experiences and for something like Artemis, they’re not cheap. It is however the absolute best way to do it and watching Artemis 1 was incredible. If you guys are full on ready to do this, go for it! Your son will love it. But you have to be ready to fight for a hotel room, stay up long hours and camp at the park, risk flight delays/pushbacks, or that it’s just not going at all. That’s the unfortunate state of nasa right now. Hope this helps! I’m hoping to go back down for future missions as well :)

Edit: Falcon 9s almost always go on time and can be seen from the Max Brewer Bridge (depending on the pad, this work well for 39A and 39B. Go further down the coast towards cocoa beach for SLC-40 launches) about once a week. They’re fun but nowhere near as impressive

2

Shrike99 t1_j6jofu2 wrote

Reply to comment by DownvoteEvangelist in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

It would work if you added some propellant to the mix. For example, add a big water tank and use that electric motor to drive a pump that sprays the water out the back at very high pressure.

Realistically you're not going to get a very good exhaust velocity with that method, so you'd instead use a different kind of electric engine to accelerate the propellant; electrostatic, electrothermal, or electromagnetic.

Indeed, the only example to date of nuclear propulsion actually being used in space was on SNAP-10A, which featured a nuclear reactor powering an electrostatic engine with cesium as the propellant.

Granted, it only worked for about an hour before it broke down, but it did work. It's a shame there hasn't been any followup in the 58 years since then.

3