NOE speeds in Striker (or elsewhere)

[Judas Iscariot]

Has anyone ever looked at the NOE speeds and wondered if they might not be a little high?

I have... especially considering a little talk I had with a pilot of an Apache who told me that they regularily pulled more than 3Gs while in NOE...

That made me start to think about the vehicles I have seen and their NOE speeds.

Notably all of th egrav vehicles that have only 1-2Gs of maneuver thrust... Kinda makes it impossible to pull a high G turn if you only have 1G of thrust...

Has anyone else considered this?

It makes those NOE speeds come down a LOT if you factor in having to maneuver at speed. It also makes for some interesting plots if you do a vector graph for the movement of a grav vehicle in Striker that is moving at its cruise speed. I discovered that in Striker terms (30 second turns with a grav vehicle with 1-1.5Gs) that moving at cruise speed the thing can only vary its course by a few degrees during the time of a turn. Less so if it is moving at its maximum speed.

Why has this not been addressed before?

 

[Pickles]

G-compensators?

 

[atpollard]

A G-compensator will not allow a 2G craft to execute a 5G turn to avoid hitting the side of a mountain.

Air frames will allow high G turns.

Striker lists the "seat of your pants" NOE speed at 40 kph (STRIKER book 4, page 3, Avionics) which is comparable to the off-road speed of a WW2 jeep. High Performance avionics will allow 120 kph NOE speed which is comparable to the highway speed of a modern car. Is that much better than a helicopter?

 

[Judas Iscariot]

It isn't a question of avionics...

I completely agree that high TL aviomics would allow for faster NOE speeds.

It is he fact that a 1G thrust drive is not going to be able to perform a 5G maneuver.

If the craft/vehicle has an Airframe (something that was not discussed in CT-Striker), then I would agree that this would help the craft/vehicle in performing higher G maneuvers (Possiby have a G rating for the airframe in question, otherwise, the craft/vehicle is limited to a 40-60kph NOE speed.

 

[Border Reiver]

I think everyone seems to be mistaking radial acceleration with direct acceleration/thrust. A 1G rated thrust will easily perform a 5G manoeuvre.

Example G Carrier travelling at 800kph makes a turn keeping the thrust so that speed through the turn is constant. This gives a speed through the turn of 222ms?¹. If the turn has a circular radius of 500m this will result in radial acceleration of around 12G. The question is whether the airframe or personnel are built to withstand those forces.

With G Compensators and future materials technology the answer is probably yes.

 

[atpollard]

Originally posted by Border Reiver:
I think everyone seems to be mistaking radial acceleration with direct acceleration/thrust. A 1G rated thrust will easily perform a 5G maneuver.

Example G Carrier travelling at 800kph makes a turn keeping the thrust so that speed through the turn is constant. This gives a speed through the turn of 222ms?¹. If the turn has a circular radius of 500m this will result in radial acceleration of around 12G. The question is whether the airframe or personnel are built to withstand those forces.

I have some doubts about that.

Without ground contact, using only thrust vectors, Grav Car A travels north and accelerates to 100 kph. The car then rotates to face due east without accelerating at all. Near frictionless momentum should continue to propel the craft due north at a constant 100 kph (I have ignored air drag). The driver should feel no lateral forces on his body.

Grav Car A then accelerates due east at 2G (the best this sport vehicle can do). The car will begin to trace a curve as the vehicle continues to slide north at 100 kph while the eastern vector will increase at about 18.6 mps2 (2G). The driver will feel a constant 2G force pushing him back into the seat as the vehicle accelerates eastward.

After about 8 or 9 seconds, the grav vehicle will be travelling north at 100 kph and east at 100 kph for a resultant vector of 141 kph and a heading of NE.

So the pilot straightens the vehicle out so the front is pointing NE (feeling a momentary lateral force as the grav car changes heading) and applies just enough thrust to maintain a constant lift and a constant forward speed. The driver should feel no lateral forces on his body.

How can the vehicle exert a lateral force greater than its acceleration with no “object” to push against?
Have I missed something?

[EDIT: An air-frame would allow the vehicle to bank a turn and use the wing pushing against the air to force a tighter turn (higher G force) but that would be a force independant of the "thrust" and based on the wing area.]

 

[Straybow]

Originally posted by Matthew Bailey:
It isn't a question of avionics...

I completely agree that high TL aviomics would allow for faster NOE speeds.

If the craft/vehicle has an Airframe (something that was not discussed in CT-Striker), then I would agree that this would help the craft/vehicle in performing higher G maneuvers (Possiby have a G rating for the airframe in question, otherwise, the craft/vehicle is limited to a 40-60kph NOE speed.

Crop dusters manage to fly seat-of-the-pants NOE much faster with only the most primitive avionics. You gotta have considerable experience in the specific type of craft.

 

[elbmc1969]

Matthew, I believe that you're fundamentally correct.

The only additional factor is that a grav tank may have a big, flat belly. If can roll the tank 80 degrees and then pull the nose around, you're going to have a lifting body whether you want to or not. (You do need to be a little careful with angle of attack to avoid "stalling" the lifting body.) Of course, you're also going to be inducing a huge amount of drag as you do this. That may not be bad if you're trying to avoid something.

This raises questions about which directions you can "project" your anti-gravity "thrust." Can you even roll a grav tank at all?

I'm not to worried about structural issues: the sort of armored hull you'll find on a grav tank would probably survive 100g accelerations.

 

[Border Reiver]

When a pilot or racing car driver refers to G's in respect of a turn they are not referring to any thrust based calculation but to radial acceleration felt when entering a uniform speed circular motion. Any driver worth their salt will tell you not to accelerate in a corner unless you want something nasty to happen, you keep a constant speed.

The formula to calculate radial acceleration is

V²/r

where V is the tangential velocity and r is the radius of the turn.


ATPollard's version will still produce radial acceleration but not uniformly throughout the turn. In this case the G force will be the root of the sum of the squares of the tangential and radial accelerations at any given point in the curve.

Mechanics, you can't escape them.

That leaves the question as to how do you steer a grav vehicle? Are there steering surfaces, is thrust projected in differing directions? Is it a combination of both? I can't see it being convenient to turn an air-raft 180º in order to reduce speed or stop.

 

[Judas Iscariot]

Border Reiver...

What you are referring to is a system that is dependent upon factors OTHER than its thrust to maneuver.

If grav vehicle was equipped with aerodymanic maneuvering surfaces, then it could easily pull turns in excess of 5Gs.

Now, I will tell you where I am getting my info about this from

Mr Brother is an Aerospace Engineer who used to work for NASA And the ESA, just to name two institutions.

He is also a pilot who has done Aerobatics and Crop Dusting.

My complaint about a grav vehicle going too fast in NOE has to do with then not having airframes in CT-Striker.

Therefore, they are limites to their thrust to turn/maneuver. If they have a 1G thrust, then th emost that they can vector is 36 ft/sec^2 (9.8m/s^2). That limits the tightness of their turns. Travelling at 800 kph is limited to a deviation from straight ahead by 9.8m/s (Moving at 800kph IS 222.2222 m/s, and its radius is NOWHERE near 500meters - closer to 2500meter radius actually). ALSO, my brother tells me that 800kph at 500 meter radius is only a 3G turn, max, probably 2.5Gs.

Joey, the Apache Pilot, also told me that the maximum Gs that they pull are equivalent or greater than those you get from a dogfighting aircraft (5-8Gs).

Basically, it comes down to what kind of terrain the vehicle is travelling over, and how much it is evading while in NOE (US Army Doctrine is to ALWAYS be evading while in NOE). If the vehice is in NOE and the trrain has a lot of trees and hills, then the NOE speed is probably no more than 5% to 10% of its max speed...

OH, one last thing... Even with an Airframe... It is going to need more than just its own thrust in order to pull those kinds of Gs... The Apache can do it because of its rotors, which act as both thrusting agent and lifting agent. AN Airplane could NEVER pull a 6G turn at the speeds (low) that the Apache is travelling at while in NOE. The same would hold true of a grav vehicle that DID have an airframe. It would need to be travelling MUCH faster than its NOE speed in order to pul the kinds of maneuvers needed for both Evasion and NOE terrain avoidance (Not to mention Pp-Ups, which would be REMARKABLY slow).

I tend to believe the Apache Pilot, and the Aerospace engineer..