3 ms·

So, someone more clever than me do the math: Can I take some solar panels, and a few of these babies and head on over to Mars? Or is this still impractical give

by mabbo 10y ago

So, someone more clever than me do the math: Can I take some solar panels, and a few of these babies and head on over to Mars? Or is this still impractical given the "micronewtons per kilowatt" levels we're talking about?

extrapickles 10y ago
Assuming you and your ship weights 1kg, it would take 9.8 gigawatts just to get it to hover in Earths gravity. This is roughly half the solar output of Germany at noon or about the same energy as the Space Shuttles boosters. Basically, if these engines prove out, they will only be used in space.
- phs318u 10y ago
  Its only usable outside of any serious gravity wells, e.g. for interplanetary and possibly intersolar travel. They would replace uses currently postulated for solar sails. Not sure, but it may also be suitable for use-cases currently postulated by small ion-thrusters as well (especially where weight is critical).
  - mikeash 10y ago
    It would be useful once you're in orbit, even deep in gravity wells, if you're patient. For example, a geosynchronous satellite with a drive like this could be launched on a rocket just big enough to get it to low-Earth orbit, and then it could gradually take itself the rest of the way. But it won't be replacing traditional rockets for that initial launch unless it's possible to increase its thrust by many orders of magnitude, and that initial launch is really the hardest part of doing space.
- mabbo 10y ago
  So you're saying it's possible then? And yes, I mean after I pay SpaceX a large sum of money to get me up into orbit. Hovering with these would definitely be a bit overbudget. I guess my question is whether a few micronewtons per kw adds up to a viable means to travel in space, or is it more like just enough to keep the satellite in orbit indefinitely?
  - danbruc 10y ago
    Once you have your spacecraft in orbit around Earth, you only have to overcome the the remaining drag of the upper atmosphere, the solar wind in case you are going towards the sun and maybe a couple of other [small] effects I am missing. But once you have enough trust to not slow down due to those effects, it just becomes a matter of time. Keep circling Earth, accelerating with whatever tiny surplus trust you have available and eventually you will reach escape velocity and off you go.
danbruc 10y ago
The papers [1] says on page 33 that the measured performance is more than two orders of magnitude better than light sails. Given that light sails are more or less considered a viable technology, it seems quite reasonable that you could get this working if you could manufacture huge and light enough solar cells. But I personally would not hold my breath - if I had to decide between quite radical new physics and measurement errors, I would certainly pick measurement errors. It seems way more likely that this is a case of faster than light neutrinos than the key to interplanetary or even interstellar travel. [1] https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU/view https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...

by mabbo 10y ago

extrapickles 10y ago

Assuming you and your ship weights 1kg, it would take 9.8 gigawatts just to get it to hover in Earths gravity. This is roughly half the solar output of Germany at noon or about the same energy as the Space Shuttles boosters. Basically, if these engines prove out, they will only be used in space.

phs318u 10y ago
Its only usable outside of any serious gravity wells, e.g. for interplanetary and possibly intersolar travel. They would replace uses currently postulated for solar sails. Not sure, but it may also be suitable for use-cases currently postulated by small ion-thrusters as well (especially where weight is critical).
- mikeash 10y ago
  It would be useful once you're in orbit, even deep in gravity wells, if you're patient. For example, a geosynchronous satellite with a drive like this could be launched on a rocket just big enough to get it to low-Earth orbit, and then it could gradually take itself the rest of the way. But it won't be replacing traditional rockets for that initial launch unless it's possible to increase its thrust by many orders of magnitude, and that initial launch is really the hardest part of doing space.
mabbo 10y ago
So you're saying it's possible then? And yes, I mean after I pay SpaceX a large sum of money to get me up into orbit. Hovering with these would definitely be a bit overbudget. I guess my question is whether a few micronewtons per kw adds up to a viable means to travel in space, or is it more like just enough to keep the satellite in orbit indefinitely?
- danbruc 10y ago
  Once you have your spacecraft in orbit around Earth, you only have to overcome the the remaining drag of the upper atmosphere, the solar wind in case you are going towards the sun and maybe a couple of other [small] effects I am missing. But once you have enough trust to not slow down due to those effects, it just becomes a matter of time. Keep circling Earth, accelerating with whatever tiny surplus trust you have available and eventually you will reach escape velocity and off you go.

danbruc 10y ago

The papers [1] says on page 33 that the measured performance is more than two orders of magnitude better than light sails. Given that light sails are more or less considered a viable technology, it seems quite reasonable that you could get this working if you could manufacture huge and light enough solar cells. But I personally would not hold my breath - if I had to decide between quite radical new physics and measurement errors, I would certainly pick measurement errors. It seems way more likely that this is a case of faster than light neutrinos than the key to interplanetary or even interstellar travel. [1] https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU/view https://drive.google.com/file/d/0B7kgKijo-p0ibm94VUY0TVktQlU...