NASA proposes new propulsion to cut Mars voyage to 3 days • Hacker News Board

Re: NASA proposes new propulsion to cut Mars voyage to 3 days

#101

Post by kpil » Tue, Feb 23, 2016, 12:29 AM UTC

05 wrote: post #94

api_or_ipa wrote: post #76

Earlier quoted context omitted.

Aerobreaking could net you some gain. Obviously, this requires a more engineeered vehicle, including possibly an ablative shield. Even at that, however, you'll be skimming very close to Mars' surface and incurring very high temperatures. Perhaps (and this is a big perhaps) we could engineer lifting body surfaces to increase the time-in-atmosphere and dissipate heat better. This is why I love playing Kerbal Space Prog…

Aerobraking from .3c would require materials many orders of magnitude more heat-resistant than known to humanity.

Yes. Stopping from 90000km/s in 100ms (more or less earth radius) might prove to be a bit hard :-)

Re: NASA proposes new propulsion to cut Mars voyage to 3 days

#102

Post by gremlinsinc » Tue, Feb 23, 2016, 8:39 AM UTC

Okay, so what I read from others is that stopping is gonna be a PITA -- so maybe Mars isn't the best target.. Why not send some huge telescope in the direction of that solar system that looks like it has an Alien Megastructure- - get as close as we can to that thing and take closer pictures of it to find out what's really going on (and other parts of the galaxy) -- imagine having a telescope like a couple solar systems away sending back data to us? -- we may to create some sort of galactic internet though - maybe using lasers and relay stations? (I honestly have no clue... we'd want to get data back and it to NOT take 50 years per data dump.) ..

Re: NASA proposes new propulsion to cut Mars voyage to 3 days

#103

Post by vannevar » Tue, Feb 23, 2016, 4:29 PM UTC

kpil wrote: post #100

vannevar wrote: post #97

Earlier quoted context omitted.

Good point. Cuts the acceleration/deceleration down to about 1 G, which would actually be useful.

Exactly how do the deceleration work... ? Hoping someone put a really big haystack on mars?

I assume they can change the angle so the thrust vector is negative. It depends on the geometry between Earth, Mars, and the spacecraft. Or maybe they accelerate to just match the orbital velocity of Mars as they arrive.

Re: NASA proposes new propulsion to cut Mars voyage to 3 days

#104

Post by dalke » Wed, Feb 24, 2016, 6:50 PM UTC

gremlinsinc wrote: post #102

Okay, so what I read from others is that stopping is gonna be a PITA -- so maybe Mars isn't the best target.. Why not send some huge telescope in the direction of that solar system that looks like it has an Alien Megastructure- - get as close as we can to that thing and take closer pictures of it to find out what's really going on (and other parts of the galaxy) -- imagine having a telescope like a couple solar syste…

It's likely very much easier to build a telescope array in this solar system than to send a telescope "a couple solar systems away".

KIC 8462852 is 1480 light years away. At 10% light speed it would take over 10,000 years to get within a few solar systems of the star.

On the other hand, a space-based interferometer with a baseline of 15 AU would have an angular resolution of:

  1.22 * 500 nm / (15 AU) = 2.7E-19 radians

giving the ability to see things at KIC 8462852 which are

  1480 light years * 2.7E-19 = 3 meters across

That's also fantastically advanced, but working backwards, to see objects 100km in size:

  (1.22  * 500 nm) / (100km / 1480 light years) = ~100,000 km

I think we can pull that off within 1,000 years, much less 10,000.

Re: NASA proposes new propulsion to cut Mars voyage to 3 days

#105

Post by Skunkleton » Thu, Feb 25, 2016, 4:57 PM UTC

wmfiv wrote: post #85

Skunkleton wrote: post #19

Earlier quoted context omitted.

Yep, that is wired for you. As far as I can tell, this plan was first proposed in the '80s. The technical challenges of a 1.21 jiggawat laser, and a gigantic sail have led to it never being attempted even though it is probably theoretically feasible.

So what changed?

Nothing as far as I can tell.