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From Theory?. A better understanding and the basis to learn more quickly. Concepts, Figures and Explanations. Primarily concerned with understanding the detail of how a balloon goes up and down. Some surprising facts and reasons why. Some practical stuff.

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From theory

From Theory?

A better understanding and the basis to learn more quickly.


Concepts figures and explanations
Concepts, Figures and Explanations

  • Primarily concerned with understanding the detail of how a balloon goes up and down.

  • Some surprising facts and reasons why.

  • Some practical stuff.

  • Understanding the principles allows you to work it out for yourself.


Equilibrium temp
Equilibrium Temp

  • What is ET at take-off for a 77,000 with an all up weight of about half a metric tonne and ambient temperature of 16 °C ?

  • Stand-up temperature approx. 40°C (200 Kg)

  • Maximum envelope temperature is ???


77 000 519 kg 86 c
77,000, 519 Kg: 86°C

  • Exact conditions

    • All up weight: 519 Kg

    • Temperature: 16 °C

    • Altitude: 120 ft (ground amsl)

    • Lift is 10 grammes (0.01 Kg)

    • From Liftcalc/MiniSim (website)

  • Warmer & Heavier

    • Temp 23 °C, AUW: 564, ET = 105 °C


Eq temp with altitude

*30 Kg fuel used, based on 500 ft/min.

What can you take from this?

Eq. Temp with Altitude


Net forces 86 c 86 5 c
Net Forces, 86°C, 86.5°C

  • Equilibrium Temperature

    • neutral buoyancy

  • Half a degree increase

    • small net force upwards


False lift
False Lift

Aerodyamic effect of a curved surface


Net forces 86 c 86 5 c1
Net Forces, 86°C, 86.5°C

  • Equilibrium Temperature

    • neutral buoyancy

  • Half a degree increase

    • small net force upwards

  • Take care

    • need to overcome inertia


Ascent rates

* Ascent rates which will be maintained.

What two points can take from this?

Ascent Rates



Ascent rates1

* Ascent rates which will be maintained.

If you know the envelope temperature can you predict what the balloon will do?

Ascent Rates


Heating 77 000 cu ft
Heating: 77,000 Cu ft

  • Rule of Thumb

    1 second of burning increases average envelope temperature by 1 °C


Cooling 77 000 cu ft
Cooling: 77,000 Cu ft

  • Rule of Thumb

    10 seconds of not burning decreases average envelope temperature by 1 °C


Staying at equilibrium flying straight and level
Staying at Equilibrium Flying straight and level

  • How often do you burn?

  • This is replacing heat due to cooling.

  • What affects this frequency?

    • Differentiate between those things that give you a higher equilibrium temp. at take- off

    • and those that affect heat input or loss.


Normal response times
Normal Response Times

  • Attaining but without haste.

  • From neutral to 100 fpm up

    • 10 seconds (2 second burn)

  • From neutral to 100 fpm down

    • 30 seconds (cooling)

  • From 300 fpm down to zero

    • 40 seconds (6 seconds of burner)

  • From neutral to ascent of 500 fpm

    • 50 seconds (16 seconds of burner)


Emergency response times
Emergency Response Times

  • Achieved by leaving burner full on, attaining and exceeding the target

  • From 100 fpm down to 100 fpm up

    • 10 seconds

  • From 200 fpm up to 200 fpm down

    • 20 second (two 5 second dumps)

  • From 300 fpm down to 300 fpm up

    • 25 seconds

  • From 500 fpm down to 500 fpm up

    • 32 seconds


What have you learnt
What have you learnt?

  • Temperature control !!

    • Short burns

  • Fast ascents – overheat.

  • Fast ascents if very high – more overheat.

  • Now we’ll look at what happens during a descent.



Descent
Descent

Resistance is proportional to the velocity squared.

Descent

Up


Descent of 100 ft min
Descent of 100 ft/min

  • What Av. Envelope Temp?

  • How to maintain ?

85.5 °C

3 Kg


Descent of 500 ft min
Descent of 500 ft/min

  • What Av. Envelope Temp?

    Temperature control not so critical

78 °C

50 Kg


Slowing a descent by increasing envelope temperature
Slowing a Descentby increasing envelope temperature

Equilib T Reached

Exceeded

Temp Up

Downward force

Deceleration rate increases

Descent rate


Above et slows more quickly
Above ET slows more quickly

  • Foot off the accelerator v. foot on break


Question
Question

  • From 300 fpm down to 0 fpm from 150 ft agl

    • 40 seconds (about 4 seconds of burner)

  • Does it matter when you put the burn in?

  • How do you avoid over burning?

  • Is the ET Exceeded?

  • How would you stop the balloon more quickly?


What have you learnt1
What have you learnt?

  • You may be falling but accelerating upwards.

  • Once you reach the equilibrium temperature your rate of deceleration will increase.

  • If you continue putting in the same burns all the way down you will over-burn.

  • Half as much is a good rule.

  • Now look at landing.


Landing
Landing

  • Tony Brown – Concorde

  • Always aim for the field before

  • Line to the ground

  • Adjust all the way down – under control

  • Stop descent slightly above ground

  • When ready, rip out in air and lock.

  • Get ready for landing.


Which field slow
Which Field ? (slow)

600 ft

Steep descent (45°) possible

3 knots


Which field fast
Which Field ? (fast)

1,000 ft

Steep descent not possible – why?

10 knots



Adrenalin
Adrenalin

  • You are in a 1,000 ft / minute descent, there is only 400 ft before you hit the ground. If you put the burner on and leave it on will you avoid hitting the ground?


Control
Control

  • Never do anything else (except fly the balloon) for more than 10 seconds.

  • If you are 500 ft above the ground a controlled descent rate is 500 ft/minute.

  • 400 ft: 400 fpm

  • 300 ft: 300 fpm

  • Etc.


To control a balloon safely
To Control a Balloon (Safely)

  • Need to know what is happening at any point in time and understand why.

  • Need to know what the balloon is capable of and its limitations.

  • Understand the basic concept of the equilibrium temperature and the wide range (60 – 120) and how these relate to what the balloon does.