Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 08-05-2015, 08:33 AM   #1
Terwin
 
Join Date: Oct 2009
Location: Plugerville
Default Reentry with Flight/TK

If a character has flight and is in the process of reentering the atmosphere (assume they start above the point where reentry heating becomes a problem), could they use their unmodified Flight advantage to reenter safely?
(assume average stats with a few hours of life support making them lightly encumbered for a flight move of 8).

Same scenario, but this time the character has unmodified TK 11 and with life support they weigh about 220lbs, giving a TK move of 2.2 when concentrating.

Notes: orbital velocity is a bit over 9km/s so it would take roughly 20 minutes to come to a stop at 8m/s/s or about 70 minutes at 2.2m/s/s

The two primary issues that require a GM's call would be:
Flight: can you use normal flight to slow down when the atmosphere is thin enough not to cause reentry heating?

TK: is your total delta-v 2.2yds/s or can you adjust your speed however much you want so long as you don't accelerate to faster than 2.2yds/s compared to your current frame of reference?
Terwin is offline   Reply With Quote
Old 08-05-2015, 09:35 AM   #2
Varyon
 
Join Date: Jun 2013
Default Re: Reentry with Flight/TK

Flight doesn't allow you to fly in Trace atmospheres, and unless I'm mistaken you actually start getting the reentry heating effect before you get to a greater than Trace atmospheric pressure. So, no, you can't use non-Space Flight to slow down enough to avoid the effect. TK, on the other hand, isn't going to be limited to atmosphere. Unmodified TK is reactionless (you don't get thrown back by pushing on something heavier than you, and you can push on yourself to fly), so you should be able to slow yourself down with that just fine. Note, however, that as you shed velocity, you'll lose your orbit; you may well end up reentering atmosphere before you've got your speed down enough to avoid burning up.
Varyon is offline   Reply With Quote
Old 08-05-2015, 10:00 AM   #3
Humabout
 
Humabout's Avatar
 
Join Date: Aug 2008
Default Re: Reentry with Flight/TK

On a side note, Flight has a limited top speed - not acceleration - (increasable with Enhanced Move). A typical object in low orbit will need to change its speed by about 17,000ish mph (Move 8,500ish), which you just can't do unless you have...well...Move 8,500ish. Otherwise, you slow yourself by your Move and then reneter in an uncontrolled manner such that even if you don't burn up, you'll impact the surface at hypersonic speeds. If you arent torn apart by the pressures on your body.

To better answer your first question: Flight would require the Space enhancement. It still won't safely land you, but it will let you try.

I have to look up the wording on TK and get back to you on the second, but even if its constant acceleration, you'll die because gravity accelerates you at 10 yards /s/s and your move is less than that. Thus you would end up in slightly reduced fall, still reneter at hypersonic speeds, and die a fiery, splatty, or torn-aparty death.
__________________
Buy My Stuff!

Dungeon Action!

My Blog: Above the Flatline.

Last edited by Humabout; 08-05-2015 at 10:05 AM.
Humabout is offline   Reply With Quote
Old 08-05-2015, 10:02 AM   #4
Dustin
 
Dustin's Avatar
 
Join Date: Oct 2004
Location: The former Chochenyo territory
Default Re: Reentry with Flight/TK

If a TK character started at geostationary orbit, could they slowly lower themselves "straight down" so as to enter the atmosphere with no relative speed to the atmosphere, and thus no heating?
__________________
My gaming blog: Thor's Grumblings
Keep your friends close, and your enemies in Close Combat.
Dustin is offline   Reply With Quote
Old 08-05-2015, 10:13 AM   #5
Humabout
 
Humabout's Avatar
 
Join Date: Aug 2008
Default Re: Reentry with Flight/TK

You only remain in geostationary orbit while you are in that orbit. As soon as you leave it, your some of your potential energy gets converted to kinetic energy via an increase in orbital speed. As you continue to force your speed lower, your orbit drops, increases orbital velocity, etc.

All of that said, you can thrust at an angle to affect a vertical landing, but it will burn a lot of fuel - enough to continually slow your orbital speed and keep your decent controlled -, requiring lots of dv equivalent, and, at the end, at least enough thrust to counter the pull of gravity.
__________________
Buy My Stuff!

Dungeon Action!

My Blog: Above the Flatline.
Humabout is offline   Reply With Quote
Old 08-05-2015, 10:18 AM   #6
Terwin
 
Join Date: Oct 2009
Location: Plugerville
Default Re: Reentry with Flight/TK

Quote:
Originally Posted by Varyon View Post
Flight doesn't allow you to fly in Trace atmospheres, and unless I'm mistaken you actually start getting the reentry heating effect before you get to a greater than Trace atmospheric pressure. So, no, you can't use non-Space Flight to slow down enough to avoid the effect. TK, on the other hand, isn't going to be limited to atmosphere. Unmodified TK is reactionless (you don't get thrown back by pushing on something heavier than you, and you can push on yourself to fly), so you should be able to slow yourself down with that just fine. Note, however, that as you shed velocity, you'll lose your orbit; you may well end up reentering atmosphere before you've got your speed down enough to avoid burning up.
Couldn't the TK just alternate shedding vertical velocity and horizontal velocity to avoid reentry until at a reasonably sedate speed?


Quote:
Originally Posted by Humabout View Post
On a side note, Flight has a limited top speed - not acceleration - (increasable with Enhanced Move). A typical object in low orbit will need to change its speed by about 17,000ish mph (Move 8,500ish), which you just can't do unless you have...well...Move 8,500ish. Otherwise, you slow yourself by your Move and then reneter in an uncontrolled manner such that even if you don't burn up, you'll impact the surface at hypersonic speeds. If you arent torn apart by the pressures on your body.

To better answer your first question: Flight would require the Space enhancement. It still won't safely land you, but it will let you try.
If the acceleration is not limited but only top-speed, why could the flier not just keep slowing down? Perhaps stop flying for a moment, then resume to slow down more?

Quote:
Originally Posted by Humabout View Post
I have to look up the wording on TK and get back to you on the second, but even if its constant acceleration, you'll die because gravity accelerates you at 10 yards /s/s and your move is less than that. Thus you would end up in slightly reduced fall, still reneter at hypersonic speeds, and die a fiery, splatty, or torn-aparty death.
The TK specified will allow the character to lift off of the surface of an earth-like body at a rate of 2.2yds/sec, so there should be something included in it which can resist he acceleration of gravity up to that which would be experienced on the surface.

Thanks for the replies thus far, this was bugging me on the way to work this morning and I wanted to get some thoughts. (hopefully none of my flying/tk characters will get themselves into this sort of situation)
Terwin is offline   Reply With Quote
Old 08-05-2015, 11:24 AM   #7
Humabout
 
Humabout's Avatar
 
Join Date: Aug 2008
Default Re: Reentry with Flight/TK

Im not sure if this is going to be clear or not. Basically, this is just a GM call Id make based on inadequate information in the description of Flight (owing to its atmospheric assumptions) and the complexities involved with choosing a reference frame for your movement, which usually doesnt matter in atmosphere.

I would set your frame of reference for measuring your speed at the point on the planets surface above which your are stationary (in the geostationary orbit you mentioned) before you start using Flight. You may vary your speed relative to this point by up to your Move. Normal rules for accelerating apply (see Space Flight enhancement). IF you have enough enhanced move (or Space Move) to counteract your orbital speed, you should be able to fly in under power. Otherwise, Id say youre looking at being a bugsplat on the planet's windshield.

As for TK, where are you getting this? I see under Levitation that it says, " For true psycbokinetic flight, take Flight (p. 52) with the Psychokinetic limitation (below)." (P. B92). That makes what you are attempting a non starter for me. You want to fly dow. To a planet, use Flight.
__________________
Buy My Stuff!

Dungeon Action!

My Blog: Above the Flatline.
Humabout is offline   Reply With Quote
Old 08-05-2015, 11:42 AM   #8
Terwin
 
Join Date: Oct 2009
Location: Plugerville
Default Re: Reentry with Flight/TK

Quote:
Originally Posted by Humabout View Post
Im not sure if this is going to be clear or not. Basically, this is just a GM call Id make based on inadequate information in the description of Flight (owing to its atmospheric assumptions) and the complexities involved with choosing a reference frame for your movement, which usually doesnt matter in atmosphere.

I would set your frame of reference for measuring your speed at the point on the planets surface above which your are stationary (in the geostationary orbit you mentioned) before you start using Flight. You may vary your speed relative to this point by up to your Move. Normal rules for accelerating apply (see Space Flight enhancement). IF you have enough enhanced move (or Space Move) to counteract your orbital speed, you should be able to fly in under power. Otherwise, Id say youre looking at being a bugsplat on the planet's windshield.
Fair enough, that is a small variation on one of the GM interpretations I had considered.

Quote:
Originally Posted by Humabout View Post
As for TK, where are you getting this? I see under Levitation that it says, " For true psycbokinetic flight, take Flight (p. 52) with the Psychokinetic limitation (below)." (P. B92). That makes what you are attempting a non starter for me. You want to fly dow. To a planet, use Flight.
From that same paragraph:
Quote:
Originally Posted by Basic
Levitation: If you have enough TK
to lift your own body weight, you can
levitate. Take the Concentrate maneuver and have your TK take Move
maneuvers to propel your body. For
true psychokinetic flight, take Flight
(p. 56) with the Psychokinetic limitation (below).
This says to me that TK levitation is a pain in the backside as far as doing other things while flying because it requires constant concentration, but it is doable if your TK level is high enough to lift you.

As the default assumption when it comes to lifting things is that they are on or near the surface of the planet, I took that to indicate that the TK levitation specified earlier could accelerate the character up to 2.2 yds/s over and above what is needed to resist the pull of up to 1G.

At the very least the character should be able to resist the pull of gravity at any altitude and wait for air friction to slow them down, similar to Flight I would think.

But then the problem is more can a few hours of life support let them slow down enough from air-friction(without burning up) to safely get down to an altitude where they can breathe.
And with TK, the character is basically lifting V. Heavy encumbrance for that whole time, so will there be some way to rest without running into problems.
(with unlimited air/time I could see the TK doing a yo-yo type motion if they are able to do so without a net loss of FP)

And it would obviously be better for the character if they could use their abilities to slow them down faster than air-friction alone.
Terwin is offline   Reply With Quote
Old 08-06-2015, 06:10 AM   #9
vicky_molokh
GURPS FAQ Keeper
 
vicky_molokh's Avatar
 
Join Date: Mar 2006
Location: Kyv, Ukraine
Default Re: Reentry with Flight/TK

We need precise details about the modifiers on Flight.

A Flight with +Space and nothing else is a reactionless thruster of infinite ΔV, and can in fact resist a 1G pull and provide extra movement in some direction (or acceleration in that direction, up to the rated maximum flight Move). Winged flight can't fly in Trace or Vacuum, but it seems that other Flight only fails in Vacuum if it lacks the Space Flight modifier.

So telekinetic Flight probably can't get into orbit (too small a velocity cap), but can slow down from an orbit and prevent falling in the process, as long as it can actually fly.
__________________
Vicky 'Molokh', GURPS FAQ and uFAQ Keeper
Also, GURPS Discord is a nice place for (faster) Q&A and overall GURPS dicussion.
vicky_molokh is online now   Reply With Quote
Old 08-06-2015, 06:28 AM   #10
Terwin
 
Join Date: Oct 2009
Location: Plugerville
Default Re: Reentry with Flight/TK

Quote:
Originally Posted by vicky_molokh View Post
We need precise details about the modifiers on Flight.
Flight (No modifiers +0%) [40] (character has average stats and light encumbrance for a flight move of 8)
TK (No modifiers) 11 levels [55] (character has average stats and with life-support weighs ~220 lbs giving TK encumbrance of Very Heavy for a TK speed of 2.2, probably rounded to 2)


At what altitude/atmospheric density would you cap flight without Space Flight?
The ISS experiences enough drag to need orbital boosts even above 200 miles, but I don't think I would let a character without +Space use flight to maneuver on EVA for example.
Terwin is offline   Reply With Quote
Reply

Tags
basic set, flight, telekinesis

Thread Tools
Display Modes

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
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 02:37 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.