Auto Rotation Re-Entry system ARRE

This project is a one presentation of one project that I did in the ESA Headsquarter in Noordwijk, into of program REXUS BEXUS

This project was presented for Sounding Rocket part (REXUS).

ARRE System

The main purpose of the ARRE will be the study of the re-entry systems based in auto-rotation property. This system is seems the autogiro's system and the re-entry system "Roton". The difference with these programs is the blades’s position, basically by having an offset between the blades and the rotor axis.

This experiment will try to recover a capsule with a payload after being released from REXUS rocket during nose cone ejection.

Low orbit re-entry speed is developed due low mesospheric drag, allowing the experiment reach high free fall speeds before entering the troposphere.

During the mesospheric branch, the rotor blades will fully deploy, having in mind the study of possible drag at these altitudes. While the atmosphere is not dense enough to generate any significant lift, the blades will trying to recover some energy in “windmill” configuration, converting it to the highest possible spin speeds. This speed will tell us how much interaction we obtained during mesospheric flight.

            As in stratosphere the density begins to grow, the accumulated spin energy will be used to damp slightly the free fall acceleration. The rotor has variable AoA (angle of attack) mechanism, allowing some actuations. After the “windmill” configuration stage, the blades will track an optimal autorotation profile so maximum energy is recovered and goal descend speed can be archived.

            The blade´s airfoil will be optimized through multidisciplinary approach, so extreme performances of whole system could be archived.

Rocket placement

Inside the REXUS rocket, the ARRE experiment will sit inside the nose cone.

This placement is necessary because to the experiment should be released in upper layers of the atmosphere and there is no need in precise apogee positioning, so the experiment can just be thrown off with the nose cone,

Flight Stages

The experiment in the Rocket, the control system will be in stand-by before the launch. The system will be just recording data of the temperature sensors and control heaters.

• At T0 seconds, in the launching moment, the control system initiates the second stage. This stage will record data from the IMU and temperature sensors and control heaters.
• At time T0+60 seconds after launch, on the nosecone ejection, the system will initialize heaters on the electronics and blades angle’s sensors.
• At T0+66 seconds all sensors will be activated in the separation moment.
• At T0+150 seconds in the apogee point, the pyrotechnics will initiate and release the blades.
• After the apogee point the system will be in a controlled falling while the auto rotation system will decrease and control the falling speed. The control system will try to reach the landing point with GPS flight control and IMU stability control.
• Near to the landing point, the ground proximity sensor will activate and initiate rotor engine to provide a softer landing.

In the ESA is typic develop in each mission patch Our Patch of mission was the famous image that the knight Quijote goes against a windmill.   You can download the study in pdf here

KERS II (Energy storage)

First and for we must know magnitudes, and now I expose the magnitude of energy for transport.

If we take motorbike Honda NC700 to make numbers

• 215Kg motorbike + 70kg pilot = 285kg
• Consumption is 4 liter per 100 kilometer.
• Density of gasoline 860 grams per liter.

Therefore the consumption is 3.44kg, an the energy of gasoline is 44Mega Joules per kg. If we take efficiency 30% to 50% in the engine.

Energy is 45.408 - 75.68 MJ to move 285Kgr about 100kms.

We take the worst case 75.68 MJ like reference.

In the post KERS I (Electric Generator/Motor), Energy recover is electric energy due to it is the most efficiency system to recover energy. However the electric energy has one problem, 1 Joules is the same that a 1 Watt per second 75.68 MJ is 75.68 MW in one second, Hoover Dam have turbines of the same power, but is this energy is no aplied in one second.

We suppose that we take this consumption with a average speed of 100km/h, therefore the energy is aplied in 3600seconds:

21kW in one hour is a value that we can manage.

If we see current batteries acid-lead with 12 V for this battery need aplied 1751 A, an this is a lot of current, normally this batteries could provide 60 - 80 A max in car or in motorbike 8A, therefore we need between 20 car batteries and with 10kg pero battery, we need 200kg in batteries acid-lead. This technology of batteries is obsolete.

The technologies with more future are

• Li-ion batteries
• Hydrogen
• Supercapacitor

Li-ion batteries
The most extended energy storage, due to of high energy and low weight, the first technologies used this energy source.

The lithium battery is light due to the lithium is light, and it provide the high capabilities of charge and discharge, but all is not perfect.

The advantages is:

• High energy storage respect are density.

The weakness is:

• 2.5 years or 200 recharges like middle life (degradation).
• Expensive for great energies.
• Delicate if don´t used correctly, very constraints parameters of discharge and recharge.
• They can blow up if we don't manage correctly.
• Recharge time.

The energy density LiPo 175 Wh/kg (MultiStar High Capacity) there fore we need 120kg of bateries for 21kW/h such as I had calculated.
 

Hydrogen
A lot of people see the future fuel, it is clean, cheap, and abundant, and it has one attribute less known, it is 3 times more powerfull than gasoline, 120MJ per kilogram, and the octane is very high.

However it has a great problem, physical laws, the Gas laws, the fuel energy is measure in kilogram, the gasoline have a density of 860kg/m^3 but the hidrogen only it have 0.0899kg/m^3, near of ten thounsand less.

In other post I follow with this idea, Hydrogen like a fuel.

Hydrogen cell

Also they are knows as Fuel cell.

With I resume in few words, use the energy of hydrogen to create electricity, and this into of electric engine is double or triple more efficiency.

Therefore we need less hydrogen for creates movement and the reaction is reversible. the problem of this energy source is newer and it need more development.

The advantages is:

• High energy storage.
• A lot parameters of discharge and recharge.
• Low maintanance.
• Cheap fuel

The weakness is:

• Low density, and high pressure for storage.
• High dangerous explosion probability in case of escape.
• Expensive (it is new technology but it will down the cost)

The energy density Fuel cell 14.4 kWh/kg (Fuel cell) there fore we need 1.46 kg of hydrogen for 21kW/h such as I had calculated.

Supercapacitor

Supercapacitor is the same of normal capacitor, but it have storage a lot of the charge than others capacitor.

Its behaviour is storage current respet a one value that is the Capacitance, and this show as voltage a direct increase between voltage

The advantages is:

• A lot parameters of discharge and recharge.
• Low maintanance.
• Recharge time.

The weakness is:

• Low energy storage if it is compared with other technologies.
• Leaks of charge, quick losse charge in funtion of time.
• New technology, it need more development

The energy density Supercapacitor 7 Wh/kg (k2-2-85-series) there fore we need 2837 kg of capacitors for 21kW/h such as I had calculated.

 

Coolant in motorbikes

The same in oil the coolant is important to know any specifications. 

Motul INUGEL

• Density 20ºC 1,070 gr/ml
• pH (100%, Mettler) 7,0 – 8,50
• Freeze Point -37ºC
• Colour yellow
• Boiling Point  +145ºC  

Castrol Motorcycle Coolant

• Colour  blour/green
• pH, n ASTM D1287 - 8.0
• ASTM D1121 ml 0.1N HCl 10
• Density  @ 15°C ASTM D4052 - 1.03
• Freeze Point ASTM D3321 ºC -25

One infortation that is important in the coolant is the Specific Heat Capacity, that it is "storage" heat capacity.

Engine provide X heat, and with more Specific Heat Capacity this means that needs more time to increase the temperature.

The problem is that the volume is not infinite, and it needs transmit heat to air surrounding, that it is not infinite but it is close. Therefore we need transmit heat between engine and the air, and coolant is only a transmission medium, and it is not a heat storage.

The typical coolant are mixture between:

• Ethylene glycol 2.4 J/(g•ºC)
• Water 4.2 J/(g•ºC)

and the Specific Heat is between those values:

If coolant have more Specific Heat Capacity.

• Advantages: more control temperature and more constant temperature
• Disadvantages: less heat transfer to air in the radiator and need more radiator surface.

Coolant with less Specific Heat Capacity is opposite.

Normally if you want extract more heat to use coolant with less Specific Heat Capacity, but you take the risk

Conclusion

With high Specific Heat Capacity, temperature changes are slower but the work temperature is higher when working.

With low Specific Heat Capacity,  temperature changes are quicker but the work temperature is lower when working, but the air stop pass trought the radiator the temperature increase quicker, for example in traffic jam or any situation when the vehicle is stopped with the engine heat.

Which is better?

The better is testing, but the normal is, if it design show 50% (vehicle manual), and you test 75% or 25%, and it depend of vehicle use, but one important thing, radiator must be clean outside and inside it.

Engine Oils in motorbikes

In a lot of motorbikes manuals we see these texts:

Use semi or fully synthetic 10W/40 or 15W/50 motorcycle engine oil which meets specification API SH (or higher) and JASO MA, such as Mobil 1 Racing 4T

or

API service classification : SE, SF, SH grade  Viscosity : SAE10W-30 (Use appropriate type of oil with viscosity satisfying the atmospheric temperature in your riding area based on the table shown on the right side.)

What is JASO and API standars? In this web (http://www.oilspecifications.org) you can see what is this standard and meaning of each oil. But If I have to make some resume:

• JASO MA: Measurerment of friction for wet clutch
• API: Measurement of chemical compatibility and deposits.

The second value is the Xw Y, and this is the important for your engine, the first number is the cold viscosity measurement Xw(40ºC - 104ºF) and the other number Y is the hot viscosity measurement (100ºC-212ºC).

And the numbers in the tables is single grade, but with 2 numbers you can see the behaviour of multigrade.

The reality of oils is if you move one grade, move all curve, the viscosity in cold of 10w-50 not is the same that 10w-30

For example, several oils 10w40:

Hot (100ºC-212ºC)

• Single grade Castrol r40, viscosity 100ºC 14.5 cSt
• Multigrade Castrol Power1 , viscosity 100ºC 13.5cSt, 
• Multigrade Castrol Power Racing , viscosity 100ºC 13.0cSt, 
• Multigrade Motul 300v, viscosity 100ºC 13.1cSt, 
• Multigrade Motul 7100, viscosity 100ºC 13.5cSt, 

Cold (40ºC - 104ºF)

• Single grade Castrol r40, tables dont show, more and less 120-180cSt
• Multigrade Castrol Power1, viscosity 40ºC 66cSt
• Multigrade Castrol Power Racing, viscosity 40ºC 83cSt, 
• Multigrade Motul 300v, viscosity 40ºC 82.1cSt, 
• Multigrade Motul 7100, viscosity 140ºC 88.8cSt,

The R40 is single grade due to it is the racing oil, and Castrol suppose that this oil only works with hot engine.
When you select the engine oil you must select the the similar grades, due to the oil viscosity depends of two parts in the engine.

1. Oil pressure in the engine. The presure provide oil flow to different parts of the engine. The kinematic viscosity provide  number of Reynolds and this low, increase the lost pressure in the internal piping of oil. Therefore the pressure in camshaft bearings is less and the film of protection is less, contrary to of reason, because we forget that the first step is carry the oil to the bearing.
2. Oil film in the bearing, the behaviour is contrary that the first point, more viscosity, more thickness oil film. (It is not  all right, if we increase the viscosity increase the minimun expsor and the oil could not enter in the gap bearing,)

Therefore, if you want select the correct oil, you must select grade oil that mark engine manufacturer. May be if you use the motor bike in winter and mountain road select the low grade and if you use the motorbike in city and summer, up the grades.

Anyway, is very important warm the engine before to ride, the oil begin to work from 40ºC to 50ºC, but the ideal point is close to 100ºC.

If I have the same grades but different oil trademark? Which is better?

The oil besides of the viscosity have other values, and the more important is the Flashpoint. Flashpoint is the second more important data, (to me). You change the oil each kms due to the oils burn and degrade into the engine. If the you increase the flashpoint, the oil keep like oil more time and not ashes, (used oil is black due to ashes).

In Racing oils you can see that this point is very high

• Single grade Castrol r40, flashpoint 220ºC (racing oil)
• Multigrade Castrol Power1, flashpoint 207ºC (Street oil) 
• Multigrade Castrol Power Racing, flashpoint 209ºC (Racing/Street oil)
• Multigrade Motul 300v, flashpoint 250ºC (Racing oil)
• Multigrade Motul 7100, flashpoint 236ºC (Racing/Street oil)

The other value that is very important el de HTHS, because y high het point with friction is very importan, if it is low, oil dont protect these points.

A lof of people say me that the temepratures into the engine is not high, but example:

Exhaust Valve is steel,and the valve clearance  is 0.2mm, and when reach work temperature this gap is 0mm, dilation constant in steel is 1.2e-5 by ºC. un one valve with lenght 120mm to grow 0.2mm you must heat to 140ºC plus room temperature, therefore 160ºC (320ºF). 

This is if we not take the values such as the rotary axis of camshaft  and  the base ons the camhead with heat  also it have lenght changes.