Author Topic: JBIS article for a proposed lunar sling launcher  (Read 6411 times)

Offline CuddlyRocket

In the latest Journal of the British Interplanetary Society (vol 58 no 9/10 Sep/Oct 2005) is an article (at p294) by Geoffrey Landis of NASA’s John Glenn Research Center (geoffrey.a.landis@nasa.gov) proposing a lunar sling launcher.

We’ve all whirled a stone horizontally around our heads on a string and then let it go, whereupon it shoots off at high velocity. The principle is the same, although on a slightly bigger scale!

To get into lunar orbit the stone, or payload, needs to be travelling at 6,050 kph, or at 13,830 kph for Mars injection. As those horror videos of astronauts being tested in centrifuges show, to keep a weight moving in a circle, there needs to be a centripetal ‘inwards’ acceleration, which is provided by the tension in the string, or tether (or centrifuge arm).

Landis analyses the case of a 50 km tether and a 1000 kg payload, and comes up with a rotation speed of 0.32 rpm with 5.7g acceleration for lunar orbit and 0.73 rpm and 16.5g for Mars injection. A bit high for astronauts (though the acceleration is inversely proportional to the length of the tether – you could halve the former by doubling the latter, for instance), but bulk cargo won’t care.

For the tether, Landis considered both a presently available material – high strength polythene fibre – and one made of fullerene carbon nanotubes (to be conservative, he assumed a tensile strength of the latter at one-tenth of the theoretical one), coming up with masses for the tether of 2500 kg and 13 kg respectively. (Note – humans have being constructing cables of much greater lengths since at least Victorian times – telegraph cables crossing oceans for instance.)

The payload cannot quite be rotated horizontally, as the tension needs to have a vertical component to counteract lunar gravity. This produces a dip from the tether hub at the centre, which amounts to a 1.5 km drop over the 50km radius. As the Moon is spherical, the ground drops away from the horizontal, and this accounts for nearly half. For the rest, Landis proposes mounting the hub on a 50 m tower atop a suitable hill.

The idea is to start with the payload hanging vertically from a short gantry off the top of the tower (the gantry is needed to keep the payload off the ground at the start). The payload is slowly rotated up to speed with the tether being paid out from a drum. To reduce stresses on the hub, Landis proposes a counterweight – he suggests a bucket of regolith (lunar dirt) – which can be more massive, and therefore need a shorter tether, as it does not need to reach the same velocities.

The energy required, provided by an electric motor, is the final total kinetic energy of the payload and counterweight, which can gradually be built up.  Landis calculates that a 100 kW motor, allowing for friction and electrical losses etc, will take 14 hours to reach the required speed, allowing 20 launches per lunar day. This can be provided by 40 m2 of solar cells.

It seems to me that constructing such a system is not a particularly difficult engineering challenge. The components are well within the masses that can be delivered by the SDLV for instance. And there is the possibility of manufacturing the solar cells and the tower structure in situ from lunar resources. As for the payload – lunar LOX delivered to LEO seems a prime early candidate.

JBIS is available to members of the British Interplanetary Society.

Offline Andy L

  • Veteran
  • Full Member
  • **
  • Posts: 260
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #1 on: 11/20/2005 11:52 AM »
That's amazing. The problem I find with it is the lack of control over the ever increasing speed of the sling prior to launch. Wouldn't a sudden loss of power or a technical issue during the speed up equal a no win situation for the payload?

Offline realtime

  • Extreme Veteran
  • Full Member
  • ****
  • Posts: 574
  • Liked: 1
  • Likes Given: 11
RE: JBIS article for a proposed lunar sling launcher
« Reply #2 on: 11/20/2005 09:05 PM »
What forces need controlling besides the reel and the motor?  There are no aerodynamic forces to contend with, so there's nothing to cause it to depart from a Newtonian trajectory.  At least, not until you release the payload.  Then there might be some oscillatory motions of the line to deal with.  What happens then?

Loss of power's not so bad if you provide a means of reeling the line back in.  A crafty mechanical engineer could design an automatic system that wouldn't require power.

Some failure of the payout or reelback system would make for a bad day.  It would become the biggest weed-whacker in the solar system.


Offline Avron

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 4915
  • Liked: 147
  • Likes Given: 150
RE: JBIS article for a proposed lunar sling launcher
« Reply #3 on: 11/21/2005 03:22 AM »
Quote
realtime - 20/11/2005  5:05 PM

What forces need controlling besides the reel and the motor?  There are no aerodynamic forces to contend with, so there's nothing to cause it to depart from a Newtonian trajectory.  At least, not until you release the payload.  Then there might be some oscillatory motions of the line to deal with.  What happens then?

Loss of power's not so bad if you provide a means of reeling the line back in.  A crafty mechanical engineer could design an automatic system that wouldn't require power.

Some failure of the payout or reelback system would make for a bad day.  It would become the biggest weed-whacker in the solar system.

LOL... Would you take a ride on this orbital slingshot?  I know I would not, too many failure modes and no way to correct.

Offline realtime

  • Extreme Veteran
  • Full Member
  • ****
  • Posts: 574
  • Liked: 1
  • Likes Given: 11
RE: JBIS article for a proposed lunar sling launcher
« Reply #4 on: 11/22/2005 03:51 AM »
No.  This puppy's for freight only.  Or maybe XTreme thrill-seekers.  It'd be a helluva ride if you didn't die.


Offline Mark Max Q

  • Going Supersonic
  • Full Member
  • ****
  • Posts: 1186
  • Liked: 12
  • Likes Given: 15
RE: JBIS article for a proposed lunar sling launcher
« Reply #5 on: 11/25/2005 01:51 AM »
Are there any diagrams to visually explain how this concept works?

Offline Orbiter Obvious

  • Extreme Veteran
  • Full Member
  • ***
  • Posts: 390
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #6 on: 12/30/2005 01:36 AM »
Welcome!

So this would swing around really fast and throw those payloads? Seems very crazy to me! :)

Online Chris Bergin

RE: JBIS article for a proposed lunar sling launcher
« Reply #7 on: 12/30/2005 01:14 PM »
Very interesting. Welcome to the site V.

Offline Sling Fan

  • Member
  • Posts: 12
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #8 on: 03/01/2006 04:40 AM »
Quote
vanilla - 29/12/2005  8:12 PM

Here's an image from AIAA paper 90-2109:  "Lunar and Mars Mission Architecture Utilizing Tether-Launched LLOX" by David Baker and Robert Zubrin, written in 1990.
Logistically, how hard would that be to place and set up on the moon?

Offline Jonesy STS

  • Full Member
  • **
  • Posts: 208
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #9 on: 03/01/2006 01:04 PM »
Quote
Sling Fan - 28/2/2006  11:40 PM

Quote
vanilla - 29/12/2005  8:12 PM

Here's an image from AIAA paper 90-2109:  "Lunar and Mars Mission Architecture Utilizing Tether-Launched LLOX" by David Baker and Robert Zubrin, written in 1990.
Logistically, how hard would that be to place and set up on the moon?

Looks like it could slide inside itself, halving the size and then the arms would fold in. So that'd fit in a Shuttle payload and I'm sure a CaLV would be able to take it up in one go?

Offline Hotol

  • Regular
  • Full Member
  • ****
  • Posts: 425
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #10 on: 03/01/2006 04:50 PM »
I think that'll be the route taken.

Offline Sling Fan

  • Member
  • Posts: 12
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #11 on: 03/06/2006 02:42 AM »
Where are we exactly with the concept? I have watched the capture device videos on the video section which were shown alongside the recent article here, but there's been nothing else of note as far as taking the concept to the stage you propose.

This is the problem. Has it already become something that was a concept that was seen to be non viable and thus is nothing more than an impressive video?

Offline Sling Fan

  • Member
  • Posts: 12
  • Liked: 0
  • Likes Given: 0
RE: JBIS article for a proposed lunar sling launcher
« Reply #12 on: 03/06/2006 02:54 AM »
Quote
vanilla - 5/3/2006  9:49 PM

Quote
Sling Fan - 5/3/2006  9:42 PM

Where are we exactly with the concept? I have watched the capture device videos on the video section which were shown alongside the recent article here, but there's been nothing else of note as far as taking the concept to the stage you propose.

This is the problem. Has it already become something that was a concept that was seen to be non viable and thus is nothing more than an impressive video?
Which system are you referring to?  A momentum-exchange/electrodynamic reboost tether in Earth orbit, or a lunar sling?

They are very different.  One operates in free space and is very long to keep the tip accelerations reasonable for human use, while the other is attached to the surface and is relatively short (in comparison) and has very high tip accelerations, but is meant for bulk cargo only (such as lunar-derived propellant or ore).

The momentum-exchange/electrodynamic reboost tether. This is something I've seen conceptual ideas of for a few years, or at least some similar. The video showing this in action plus some of the documentation surrounding it point to a good project effort, but then nothing.

I'm hoping for some good news that this is still alive as what would be a big leap, as mentioned on another thread? Cutting out a lot of the propellant/fuel which we always have to carry with us just to get to a ppint where we can then look at missions. A reusable transportation system is an absolute passion for me and I'm desperate to hear it's still possible.

I know this should be on the sling me to the moon thread, but take that as a sign of my efforts to hear more.

Offline kfsorensen

  • aerospace and nuclear engineer
  • Full Member
  • ****
  • Posts: 1541
  • Huntsville, AL
    • Flibe Energy
  • Liked: 99
  • Likes Given: 0
Re: JBIS article for a proposed lunar sling launcher
« Reply #13 on: 05/04/2010 03:59 AM »
I still wonder if we couldn't build a smaller version of this idea on earth.

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 3538
  • Liked: 471
  • Likes Given: 123
Re: JBIS article for a proposed lunar sling launcher
« Reply #14 on: 05/04/2010 11:47 AM »
btw.. My rather poor maths came to pretty much the same values for that rotovator idea, to deliver something from low lunar orbit to the surface: 50km tether at about 6g

(or actually, I deduced 300km for 1g, but six times smaller radius means six times more force, given the same 1.7km/s velocity.)

Offline RobLynn

  • Full Member
  • **
  • Posts: 239
  • Per Molestias Eruditio
  • London
  • Liked: 24
  • Likes Given: 24
Re: JBIS article for a proposed lunar sling launcher
« Reply #15 on: 11/09/2017 09:00 PM »
A lunar sling would potentially dovetail well with a purpose built SpaceX's 50m tall ITS.  Providing a suitable hill on the lunar surface can be found.

All necessary sling components + deployable solar panels and as many additional electric propulsion systems+casings as possible could be built into the nose of a single-use (no heat shielding or wings) ITS ship, and it should be possible to fill up the tanks with 1-2000tonnes of regolith after landing to provide the base stability required to counteract the tipping moment of the lateral sling on top.

Might then be able to provide a lunar resource and even emergency human-return system from the lunar surface for relatively low initial capital costs and without needing to manufacture rocket fuel on the Lunar surface.
I'm a "glass is twice as big as it needs to be" kinda guy

Online john smith 19

  • Senior Member
  • *****
  • Posts: 6058
  • Everyplaceelse
  • Liked: 788
  • Likes Given: 4893
Re: JBIS article for a proposed lunar sling launcher
« Reply #16 on: 11/10/2017 09:03 AM »
I still wonder if we couldn't build a smaller version of this idea on earth.
Not really.

All ground based Earth to orbit launch systems, that aim to accelerate the payload to some fraction of orbital speed by rotation, suffer the same problems.

1)They impose centripetal (side) accelerations on the payload, even if the front-to-back acceleration is quite mild.

2)To achieve any significant reduction in complexity they need to get to a substantial fraction of orbital. That means they will be traveling at near Mach 23 near the Earths surface before release. The "boom carpet" will be heard on the next continent.

3)The payload package will experience re-entry levels of heating on the way out of the atmosphere. Unfortunately so will the tether.

On the Moon, yes. On Mars, (at 1/160 of Earth pressure) maybe (along with mass drivers) but Earth?
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline sanman

  • Senior Member
  • *****
  • Posts: 3850
  • Liked: 485
  • Likes Given: 7
Re: JBIS article for a proposed lunar sling launcher
« Reply #17 on: 11/10/2017 10:31 AM »
Could this type of launch apparatus be set up inside a 100km-diameter crater, to compartmentalize it from its surroundings?

Offline Asteroza

  • Full Member
  • ****
  • Posts: 480
  • Liked: 52
  • Likes Given: 2
Re: JBIS article for a proposed lunar sling launcher
« Reply #18 on: 11/12/2017 10:46 PM »
Could this type of launch apparatus be set up inside a 100km-diameter crater, to compartmentalize it from its surroundings?

Depends on a couple things there.

Will you need a touchdown/takeoff circular track for the payload? Will the crater rim lip need a notch to pass the payload after release? How much of a backstop do you need for the counterweight if it gets loose?

Tags: