RSS iconTwitter iconFacebook icon

The Trek BBS title image

The Trek BBS statistics

Threads: 147,639
Posts: 5,837,524
Members: 26,161
Currently online: 474
Newest member: mike7007

TrekToday headlines

Retro Review: Elogium
By: Michelle Erica Green on Aug 28

Trek Swype Keyboard
By: T'Bonz on Aug 28

Meaney In Talks For McGuinness Role
By: T'Bonz on Aug 27

Stewart And Son To Act Together
By: T'Bonz on Aug 27

Quinto: If I Wasn’t An Actor…
By: T'Bonz on Aug 27

Star Trek Beyond Update
By: T'Bonz on Aug 27

Red Shirt Diaries Returns Next Month
By: T'Bonz on Aug 26

ISS Astronaut May Join Trek Fan Film
By: T'Bonz on Aug 26

Quinto Sports New Trek Uniform
By: T'Bonz on Aug 26

Star Trek: Renegades Released Early
By: T'Bonz on Aug 25


Welcome! The Trek BBS is the number one place to chat about Star Trek with like-minded fans. Please login to see our full range of forums as well as the ability to send and receive private messages, track your favourite topics and of course join in the discussions.

If you are a new visitor, join us for free. If you are an existing member please login below. Note: for members who joined under our old messageboard system, please login with your display name not your login name.


Go Back   The Trek BBS > Entertainment & Interests > Science and Technology

Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

Reply
 
Thread Tools
Old August 29 2015, 06:26 PM   #1
publiusr
Rear Admiral
 
Flyby asteroid rotovator

One of the problems with space elevators will be the constant attack by atomic oxygen--not to mention icing loads near the ITCZ. (Convection is deeper near the equator)

One concept I had was an asteroid bola with a tail that could fly by Earth, deposit a large load, and yank a load upward.

Doctor Pat from Next Big Future was kind enough to supply the math: http://nextbigfuture.com/2015/08/sup...tic-space.html (Scroll down)


Minimum velocity of the center of mass of the rotovator is the minimal orbital velocity of 7.8 km/s
Velocity of rotor tip at pickup from the ground needs to be about 0, or close enough to make no difference to this level of calculation.
Minimum rotor length is going to be the height of LEO, so about 100 km.
Maximum velocity of the rotor tip in the atmosphere should be lets say no more than mach 6 (~2 km/s) until it reaches at least 20 km in altitude. Based on the articles about hypersonic aircraft and what they can handle.

Let's put that together.

If we assume the tip of the rotor is sort of accelerating straight up with respect to the earth's surface, that means that the tip goes from 0 to 2000 m/s in 20 km.
v[sup]2[/sup] = 2 x Acceleration x distance
4 000 000 = 40 000 x Acceleration
Acceleration = 100 m/s/s = 10g (actually, that turned out rather reasonable)

Accel. = v[sup]2[/sup] / R (note, now V is relative to rotor center, not Earth)
V = twice the rotor center speed = 15.6 km/s
R (rotor radius) = 2.4 million meters = 2400 km.

OK, that's a lot higher than our original Minimum rotor length, so it meets that limit too.

But a rotor that long does not need to going to not be travelling at LEO speeds, so we can slow everything down a bit. But the minimum is still 6.7 km/s, so it isn't enough to make much difference.

Anyway, the real problem is that to have a reasonable speed through the thick parts of the atmosphere, your rotor needs to be so long that you are looking at a 2400 km long rotor. Not quite a space elevator cable, but it would be a serious material strength problem."


That's only 1,500 miles--not 22,500--to--60,000.
Better

Lunar Elevator meeting http://www.meetup.com/Florida-Space-...nts/224287435/

Supertall towers http://nextbigfuture.com/2015/08/an-...ll-towers.html
http://nextbigfuture.com/2015/08/mod...-and-zinc.html

Misc SLS art
http://www.keithmcneill.pwp.blueyonder.co.uk/SLS1g.jpg
http://www.keithmcneill.pwp.blueyonder.co.uk/SLS2k.jpg
http://www.keithmcneill.pwp.blueyonder.co.uk/SLS4e.jpg
http://www.keithmcneill.pwp.blueyonder.co.uk/SLS3j.jpg
Magnetic hole http://nextbigfuture.com/2015/08/met...ole-moves.html
Light fibers http://nextbigfuture.com/2015/08/sup...ld-create.html

ISS seen from the ground http://0e33611cb8e6da737d5c-e13b5a91...1440524457.jpg

Last edited by publiusr; August 29 2015 at 09:40 PM.
publiusr is offline   Reply With Quote
Old August 29 2015, 10:16 PM   #2
PurpleBuddha
Rear Admiral
 
PurpleBuddha's Avatar
 
Re: Flyby asteroid rotovator

Here's a vid about something very similar. I like the idea! It seems more feasible than a space elevator.

PurpleBuddha is offline   Reply With Quote
Old Yesterday, 03:24 PM   #3
ThunderAeroI
Rear Admiral
 
ThunderAeroI's Avatar
 
Location: Perpetually being chased by airplanes
Re: Flyby asteroid rotovator

^, Was that video narrated by Krepky?
__________________
No Where to be found, but everywhere you are - I'll be there looking for ways to save your life.
ThunderAeroI is offline   Reply With Quote
Old Yesterday, 08:09 PM   #4
PurpleBuddha
Rear Admiral
 
PurpleBuddha's Avatar
 
Re: Flyby asteroid rotovator

They do sound similar. He even acknowledges it in one of his other videos.
PurpleBuddha is offline   Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 11:07 AM.

Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
FireFox 2+ or Internet Explorer 7+ highly recommended.