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[Deadmeat1471]

Does anyone know a way to extremely simplify the acceleration/speed calculation for physics?

Example, i'm thinking of rockets:

A Saturn-V rocket has approx 7.6 million lb's thrust for its first SIB stage.
Its weight is approximately 6.6 million lbs including payload.

This leaves approximately 1 million lb's of upward thrust?(for approximately 400 seconds)   How can i translate this into a ballpark figure for speed. I'm thinking of games here, I dont need to calculate every second of drag and air density, I just need a ballpark figure to mark against several rockets and designs and use for a game.
All I need to use are the average speed for a rocket of this amount of thrust, and approximately what % of that is lost to drag/air resistance.
I know there are complex mathmatical formulas for calculating this, I simply don't understand them, I am not a physicist. They are no use to me and I don't feel confident I couldnt learn to understand the equation in a short time.

I would have used figures from an actual Saturn-V launch for the speed, but I couldn't find any.

I'm thinking of about 5 calculations for launch, one lift off and then every 20km or so.(or less)

Lift off/Ground
Troposphere
Stratosphere
Mesosphere
Thermosphere


Example, thrust would result in 500f/s base speed average up to the troposphere, 50% of that being lost to dragso 250f/s actual speed.
from trop to strat, 40% lost, mes to therm, 30% and so on. (these are explanatory figures, not the ones I plan to use.)
At 100km this drops to 0(basicly.)

Any help would be appreciated!

Notes for me about atmospheric pressure

Spoiler (click to show/hide)

50% of the atmosphere by mass is below an altitude of 5.6 km (18,000 ft).
90% of the atmosphere by mass is below an altitude of 16 km (52,000 ft). The common altitude of commercial airliners is about 10 km (33,000 ft) and Mt. Everest's summit is 8,848 m (29,029 ft) above sea level.
99.99997% of the atmosphere by mass is below 100 km (62 mi; 330,000 ft), although in the rarefied region above this there are auroras and other atmospheric effects. The highest X-15 plane flight in 1963 reached an altitude of 108.0 km (354,300 ft).

To be honest...

Does anyone forsee a problem with having the average speed for the game be:

1,000,000 pounds net thrust =
5km/s speed(0.5% of the thrust lb's)
minus - air pressure/gravity at lower levels so say 30% of this until 80km approx
minut - 20% aerodynamics modifier(based on the size/quality of rocket aerodynamics)
*2km/s is the required speed for a rocket to reach LEO, apparently. So this would not be entirely unrealistic.

*sums no longer relevant, have tweaked.

I know this isn't realistic, I'm talking about a functional model. I'll do a few test runs to see how this works.

[KaelGotDwarves]

This isn't rocket science... oh wait.

Okay, let me try to explain it using an easy example from wiki -

T = (dm/dt)v

where:
T is the thrust generated (force)
(dm/dt) is the rate of change of mass with respect to time (mass flow rate of exhaust); - because as fuel leaves the rocket as it converts fuel mass to propulsive energy. This can be at various rates. Assume a constant rate following launch unless you want to start using basic calculus.
v is the speed of the exhaust gases measured relative to the rocket.

For vertical launch of a rocket the initial thrust force must be more than the force of weight due to gravity.

The real life example given is: Each of the three Space Shuttle Main Engines can produce a thrust of 1.8 MN (Meganewtons), and each of the Space Shuttle's two Solid Rocket Boosters 14.7 MN, together 29.4 MN. Compare with the mass at lift-off of 2,040,000 kg, hence a weight of 20 MN.

[Deadmeat1471]

This isn't rocket science... oh wait.

Okay, let me try to explain it using an easy example from wiki -

T = (dm/dt)v

where:
T is the thrust generated (force)
(dm/dt) is the rate of change of mass with respect to time (mass flow rate of exhaust); - because as fuel leaves the rocket as it converts fuel mass to propulsive energy. This can be at various rates. Assume a constant rate following launch unless you want to start using basic calculus.
v is the speed of the exhaust gases measured relative to the rocket.

For vertical launch of a rocket the initial thrust force must be more than the force of weight due to gravity.

The real life example given is: Each of the three Space Shuttle Main Engines can produce a thrust of 1.8 MN (Meganewtons), and each of the Space Shuttle's two Solid Rocket Boosters 14.7 MN, together 29.4 MN. Compare with the mass at lift-off of 2,040,000 kg, hence a weight of 20 MN.

I know this, but to translate this into a speed I need to add factors such as the exaust gas speed and mass flow rate of exaust as you said - I do not know how to do this. *perhaps you could give me a constant flow? 

[KaelGotDwarves]

You need to decide on what fuel you're using, how powerful it is, and how much of it you're burning per second.

[Deadmeat1471]

You need to decide on what fuel you're using, how powerful it is, and how much of it you're burning per second.

Lets say I use LH2/LOX as in Saturn-V first stage F-1 rockets....

Specific impulse is 263 s (2.58 kN·s/kg)

however this needs 'real worlding'.

'The F-1 burned 3,945 pounds (1,789 kg) of liquid oxygen and 1,738 pounds (788 kg) of RP-1 each second, generating 1,500,000 pounds-force (6.7 MN) of thrust'
This equated to a flow rate of 413.5 US gallons (1,565 l) of LOX and 257.9 US gallons (976 l) RP-1 per second. During their two and a half minutes of operation, the five F-1s propelled the Saturn V vehicle to a height of 42 miles (68 km) and a speed of 6,164 miles per hour (9,920 km/h).

AHHAH! I found what I needed, thanks for the input kael, I'll fiddle with tis for a bit.

One thing I could do with is knowing exactly  what 'dm/dt' is refering to. Also what measurement that is in, as the flow rate is about 700 gallons total..... ?

[Deadmeat1471]

removed.

[Virex]

dm/dt is the derivative of the mass to the time, so in essence it's how much the mass changes per second. If that value can be assumed a constant for your engine (it burns x gallons per second at all times) you've got a constant thrust. Else, T=v*dm/dt gives you a relation between the time and the thrust.

[Deadmeat1471]

dm/dt is the derivative of the mass to the time, so in essence it's how much the mass changes per second. If that value can be assumed a constant for your engine (it burns x gallons per second at all times) you've got a constant thrust. Else, T=v*dm/dt gives you a relation between the time and the thrust.

Ok so lets say the flow rate is a fixed 700 gallons a second. The Exaust gas speed is a fixed 3,560 m/s taken from the SSME.

T = 3,560 m/s(taken from SSME)*700? = whatever?

[Virex]

Gallons is a unit of volume, so you'd need to multiply the result by the density of your fuel. If you don't know the density, 0.8 kg/m³ (needs to be converted to kg/gallon if you want thrust in newtons) is a decent guess for most fuels (though it may be different for LOX/LH, as liquid hydrogen has a very, very low density)

[Deadmeat1471]

Gallons is a unit of volume, so you'd need to multiply the result by the density of your fuel. If you don't know the density, 0.8 kg/m³ (needs to be converted to kg/gallon if you want thrust in newtons) is a decent guess for most fuels (though it may be different for LOX/LH, as liquid hydrogen has a very, very low density)

I'll check this out and get back.