Rather than putting the elevator on Mars it may be better to attach it to the moon Phobos. Aim the ribbon at Mars and use a rocket powered aircraft for the last 100km.
on G-LOC in prone positions, presumably before the development of flight G-suits: "Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.[3]"The Olympus Mons Mass Driver: 300km length, up to 17G acceleration for 59.4 seconds in an evacuated tube, up to 10.1km/s muzzle velocity at 60pa summit pressure, sufficient to achieve a shortened direct transfer back to Earth, and just about what you need to meet up with an Aldrin cycler.{snip}
Quote from: A_M_Swallow on 05/26/2015 03:38 pmRather than putting the elevator on Mars it may be better to attach it to the moon Phobos. Aim the ribbon at Mars and use a rocket powered aircraft for the last 100km.Phobos is tidally locked, so at least you don't have to worry about your ribbon facing Mars. But it presents other problems. Phobos is actually LOWER than geostationary orbit, so the ribbon would move around as phobos moves around in orbit. Might not be a problem going down, it's actually even better- just wait until you're at the spot you want at- but if you wanted to get up to it you'd need a launcher that can get you up to speed relative to Mar's rotation. What would that be, a few hundred km/h? How would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground? It moves around the planet with Phobos, and you need to reach it with a craft that's also moving very quickly; does this make a dangling ribbon too difficult?{snip}
Quote from: Dudely on 05/27/2015 12:34 pmQuote from: A_M_Swallow on 05/26/2015 03:38 pmRather than putting the elevator on Mars it may be better to attach it to the moon Phobos. Aim the ribbon at Mars and use a rocket powered aircraft for the last 100km.Phobos is tidally locked, so at least you don't have to worry about your ribbon facing Mars. But it presents other problems. Phobos is actually LOWER than geostationary orbit, so the ribbon would move around as phobos moves around in orbit. Might not be a problem going down, it's actually even better- just wait until you're at the spot you want at- but if you wanted to get up to it you'd need a launcher that can get you up to speed relative to Mar's rotation. What would that be, a few hundred km/h? How would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground? It moves around the planet with Phobos, and you need to reach it with a craft that's also moving very quickly; does this make a dangling ribbon too difficult?{snip}According to Wikipedia Phobos moves at 2.138 km/s, it orbits at ~6000 km above the surface of Mars and its orbital period is 7 hours 39.2 minutes.https://en.wikipedia.org/wiki/Phobos_%28moon%29The closest approximation to docking to the end of the ribbon I can think of is an in-flight refuelling. The docking port may need its own RCS to handle small movements. Large movements - just accept it is a gigantic pendulum and plan for instantaneous launchs.
So, using a cord dangling from phobos as a space elevator saves us about 15% of the total energy needed to leave Mars. Meh.
Quote from: Dudely on 05/27/2015 04:14 pmSo, using a cord dangling from phobos as a space elevator saves us about 15% of the total energy needed to leave Mars. Meh.But dangle a cord of the other side of Phobos to well past geo synch altitude and you can be dangling off that cord and launch back to Earth or to other system destinations (yes timing is everything, but a surprising number of launch windows would exist)
An orbital period of 7 hours 39.2 minutes combined with Mar's rotational period of 24 hours 39 minutes means a cord hanging from this down to 100km above the surface would be moving, relative to the rotating surface of Mars, at something just shy of 2,000 km/h, which is about 0.5 km/s. This represents 10% of escape velocity from Mars. Once you go up the thread to Phobos, you will be roughly 9,500 km above mars and travelling at about 2.0 km/s. So, using a cord dangling from phobos as a space elevator saves us about 15% of the total energy needed to leave Mars. Meh.
Quote from: A_M_Swallow on 05/27/2015 03:15 pmQuote from: Dudely on 05/27/2015 12:34 pmQuote from: A_M_Swallow on 05/26/2015 03:38 pmRather than putting the elevator on Mars it may be better to attach it to the moon Phobos. Aim the ribbon at Mars and use a rocket powered aircraft for the last 100km.Phobos is tidally locked, so at least you don't have to worry about your ribbon facing Mars. But it presents other problems. Phobos is actually LOWER than geostationary orbit, so the ribbon would move around as phobos moves around in orbit. Might not be a problem going down, it's actually even better- just wait until you're at the spot you want at- but if you wanted to get up to it you'd need a launcher that can get you up to speed relative to Mar's rotation. What would that be, a few hundred km/h? How would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground? It moves around the planet with Phobos, and you need to reach it with a craft that's also moving very quickly; does this make a dangling ribbon too difficult?{snip}According to Wikipedia Phobos moves at 2.138 km/s, it orbits at ~6000 km above the surface of Mars and its orbital period is 7 hours 39.2 minutes.https://en.wikipedia.org/wiki/Phobos_%28moon%29The closest approximation to docking to the end of the ribbon I can think of is an in-flight refuelling. The docking port may need its own RCS to handle small movements. Large movements - just accept it is a gigantic pendulum and plan for instantaneous launchs.An orbital period of 7 hours 39.2 minutes combined with Mar's rotational period of 24 hours 39 minutes means a cord hanging from this down to 100km above the surface would be moving, relative to the rotating surface of Mars, at something just shy of 2,000 km/h, which is about 0.5 km/s. This represents 10% of escape velocity from Mars. Once you go up the thread to Phobos, you will be roughly 9,500 km above mars and travelling at about 2.0 km/s. So, using a cord dangling from phobos as a space elevator saves us about 15% of the total energy needed to leave Mars. Meh.
Quote from: Burninate on 05/27/2015 01:24 pmon G-LOC in prone positions, presumably before the development of flight G-suits: "Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.[3]"The Olympus Mons Mass Driver: 300km length, up to 17G acceleration for 59.4 seconds in an evacuated tube, up to 10.1km/s muzzle velocity at 60pa summit pressure, sufficient to achieve a shortened direct transfer back to Earth, and just about what you need to meet up with an Aldrin cycler.{snip}The payload will need a fairing. Mars may have a thin atmosphere but at 10.1km/s there will still be significant heating.
Quote from: Dudely on 05/27/2015 04:14 pmQuote from: A_M_Swallow on 05/27/2015 03:15 pmQuote from: Dudely on 05/27/2015 12:34 pmQuote from: A_M_Swallow on 05/26/2015 03:38 pmRather than putting the elevator on Mars it may be better to attach it to the moon Phobos. Aim the ribbon at Mars and use a rocket powered aircraft for the last 100km.Phobos is tidally locked, so at least you don't have to worry about your ribbon facing Mars. But it presents other problems. Phobos is actually LOWER than geostationary orbit, so the ribbon would move around as phobos moves around in orbit. Might not be a problem going down, it's actually even better- just wait until you're at the spot you want at- but if you wanted to get up to it you'd need a launcher that can get you up to speed relative to Mar's rotation. What would that be, a few hundred km/h? How would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground? It moves around the planet with Phobos, and you need to reach it with a craft that's also moving very quickly; does this make a dangling ribbon too difficult?{snip}According to Wikipedia Phobos moves at 2.138 km/s, it orbits at ~6000 km above the surface of Mars and its orbital period is 7 hours 39.2 minutes.https://en.wikipedia.org/wiki/Phobos_%28moon%29The closest approximation to docking to the end of the ribbon I can think of is an in-flight refuelling. The docking port may need its own RCS to handle small movements. Large movements - just accept it is a gigantic pendulum and plan for instantaneous launchs.An orbital period of 7 hours 39.2 minutes combined with Mar's rotational period of 24 hours 39 minutes means a cord hanging from this down to 100km above the surface would be moving, relative to the rotating surface of Mars, at something just shy of 2,000 km/h, which is about 0.5 km/s. This represents 10% of escape velocity from Mars. Once you go up the thread to Phobos, you will be roughly 9,500 km above mars and travelling at about 2.0 km/s. So, using a cord dangling from phobos as a space elevator saves us about 15% of the total energy needed to leave Mars. Meh.More than just 15%.You can always keep climbing beyond Phobos.
A ground anchored space elevator on Mars would require moving Phobos, which I recall was brought up in another thread on this site. But a double space elevator anchored on Phobos combined with single stage to tether is still useful. That 15% deltaV savings coming up translates to more than that for mass ratio.An incoming spacecraft docks to "Phobos Far" station at a Lagrange point. Passengers and cargo travel down a tether to Phobos, take a railroad to the Phobos Low tether, drop to Mars. Going the other way a single stage spacecraft delivers the pod which catches the Phobos Low tether. A fair amount of infrastructure to install, but saves a lot of propellant going to and from Mars.Quick related question, where is Demos relative to the Mars-Phobos outer Lagrange point? If that's a problem might we still salvage advantage from a similar tether set on Demos?
{snip}But a double space elevator anchored on Phobos combined with single stage to tether is still useful. That 15% deltaV savings coming up translates to more than that for mass ratio.An incoming spacecraft docks to "Phobos Far" station at a Lagrange point. Passengers and cargo travel down a tether to Phobos, take a railroad to the Phobos Low tether, drop to Mars. Going the other way a single stage spacecraft delivers the pod which catches the Phobos Low tether. A fair amount of infrastructure to install, but saves a lot of propellant going to and from Mars.{snip}
Quote from: nadreck on 05/27/2015 06:09 pmBut dangle a cord of the other side of PhobosYou'd need a counter-weight on the end of that cord.
But dangle a cord of the other side of Phobos
Quote from: Dudely on 05/27/2015 12:34 pmHow would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground?The closest approximation to docking to the end of the ribbon I can think of is an in-flight refuelling.
How would you dock with the end of the ribbon and keep it stable if it cannot be anchored to the ground?