ThunderStruck Progress.

Pajero Jan 2016

Pajero Tracking Vehicle Update

We are on the move after several delays. The proof is in the progress since our last post. We are now talking boosters from our balloon platform to get us to space and we are working on our technology. Balloon test flights are being planned for late January / early February

So lets look at what my son, Jason (13), and I have done and are doing about the tracking vehicle. We will have more, but we are planning on at least having our 4WD SUV ready for the trans-sonic test as soon as we get this approved by CASA – the Australian Civil Aviation Safety Authority.

read more

ThunderStruck X-2 Speed Profile

Balloon Flight with ThunderStruckCalculating ThunderStruck X-2 Speed

Recently we spoke about the spreadsheet that we have created to calculate the speed to be achieved by the ThunderStruck X-2 craft. We took into account a range of figures and that gave us some big design changed to ensure that we could meet the Mach 1.5 speed that we wanted for the experiments on board. Those changes took into account the drag of the vehicle, the angle of the nose cone, the size of the fuselage, gravity at altitude, air density and more. For the sake of the initial calculations we did not bother with the drag of hitting Mach 1 as we believed the air density to be so thin that it would not stop us achieving the speed that we needed.

I am pleased to say that team member Todd Hampson has now incorporated the transonic factors and ongoing supersonic factors into the spreadsheet and I am pleased to say that we were right. There is very little variation in our calculated speed if dropped from 45km altitude. Lower altitudes certainly had issues, but not if dropped from 40km and above. Although we are aiming for 45km using hydrogen, it is possible conditions like potential grass fires my limit us to Hydrogen

The addition factors that we have added to the spreadsheet are:

  • Base Drag
  • Area Rule
  • Transonic Wave Drag
  • Supersonic Wave Drag
  • Friction Drag

Remember that this spreadsheet is designed to measure an aircraft in a vertical dive into the ground. You can see it slow with thick air to very low speeds. None the less we intend to transition to horizontal flight at below 10km altitude, to the remainder of the graph becomes meaningless at that point.

One of the outputs of the spreadsheet is a set of figures. Below are the figures for 45km altitude release and below that for 40km altitude release. Both heights break Mach 1 sea level equivalent.

 45km stats

Above: Figures showing the results of a 45km release.

Below:  Figures showing the results of a 40km release.

40km stats

Mach 1 at Sea Level and Mach 1 at Altitude

Simply put, altitude does not really change the speed of sound. Temperature does. It is the biggest factor. Because the speed of sound is lower at altitude where the temperature can be as low as -60C, many people feel as if we are cheating if we only break Mach 1 at the altitude that we are traversing. They want to see the speed of sound broken as if we were doing it at sea level. We have provided those calculations here. The chart automatically compensates for the increased effects of the speed of sound at a given altitude by assuming a standard set of temperatures at those altitudes. These vary by time of year and region. We will publish the set of tables that we have used for this in a future post for reference.

For our purposes, the figures used will be accurate enough for the calculations. Why do we know this? Because they do not vary much at the altitudes that we are breaking the sound barrier. The coldest air in our flight will be in the jet stream and is well below 20km altitude.

We intend to give others on-line access to our spreadsheet in the near future, when we are assured all the bugs are ironed out. At this time the spreadsheet looks stable and accurate.

Below is our Velocity Profile showing Max speed in Mach figures. Remember the speed of sound changes with altitude and this is adjusting the Mach figures for the air temperature at each altitude point. The bump near the 15km is the point where the craft decelerates going through the speed of sound. Given its proximity to the ground and the density of air, it is very possible that we will hear a sonic “boom” from this event.

 45km Velocity Profile

The graph below is the Acceleration Profile in Gee Force. The bump at 15km is showing the additional drag going through the sound barrier to subsonic speeds. there is a similar bump centred at 39.5km, but the air is so thin, it is extremely attenuated and not visible and thus it has little effect.

45km Acceleration Profile

Below is a graph showing the Velocity vs Time for the first 125 seconds. After this time, the aircraft will level out.

45km velocity vs time - 125 seconds
From the top graph – Velocity Profile – if Thunderstruck X-2 continued its dive to the ground, it would hit at Mach 0.27 or 320kph . This is a lot slower than the Mach 1.5 it achieved at 39.5km. Lets hope that the landing will be a lot smoother!

Aerodynamics of Supersonic Craft

Supersonic Glider-spacecraftSupersonic Shock Waves

by Robert Brand

Phase 1 Test Craft

As you all know by now, Jason, my 12 year old son, will attempt to break the sound barrier mid year – he will be 13 by then. This is the first test of a high drag system that should limit our airspeed at supersonic speeds. It is the Phase 1 testing that we talk about in our documents. We need to go fast for this experiment, but returning from space we need to slow down. Our transonic tests will be with a very different looking craft than our future spacecraft.

To the right, you will see where Jason’s design started. As you may have noticed, the ThunderStruck’s current design looks nothing like the image to the right. At each stage he has had to modify the craft to achieve the goals of going supersonic and get up to around 2,000kph ThunderStruck Design and 1-2 size measurementswith full stability. Only then will we deploy the experiment and hopefully slow the craft dramatically. As you are aware, it now looks more like the craft to the left. These are massive differences and we will explore the choices he made in another post. Right now we are looking at how we get rid of the major shock waves and also how our Phase 2 test aircraft may look. The main differences in the 2 craft are:

  • No supersonic Spike
  • No central tail
  • Winglets above and below with a ganged rudder
  • Delta wings that have two angles of protrusion from the fuselage
  • Elevators and ailerons are at the rear of the wing
  • The wing extends to the rear of the craft

Phase 2 Test Craft

In Phase 2 the craft that we design will need to travel straight up into space on a sounding rocket. We will separate from the rocket and continue our climb (momentum) to apogee (top of the flight) and then fall back to earth. Apogee may be as high as 200km. The air is so thin that we can conduct what we call weightlessness experiments for several minutes. Once the air starts to create drag, the experiments will end as the craft will slow. At this time we do not want the craft to accelerate further, but it will. Unless we feather the wings(like Virgin Galactic’s Spaceship 2) or create massive drag in some other way (our Phase 1 experiment) we will go too fast for our craft’s well-being. We need to go slow as possible. We do not want to have to slow with unusual braking as this may de-stabilise the small craft.

Hyabusa reentry sequencWe could use a capsule, an ablative heat shield and a parachute like JAXA’s Hyabusa, but we are creating a winged vehicle, although the capsule will always be another option. I guess the cat’s is out of the bag. We will have a couple of configurations possible with capsule or winged reentry as an option. The ThundrStruck craft will be a modular design in the style and electronics. The picture to the right is the landing sequence for JAXA’s Hyabusa that landed in the centre of Australia. It is not complicated, but you do have to know what you are doing and the downside is that it lands where ever the winds take the parachute.

I want to fix that problem for those customers that need a precision landing or effectively or a smooth landing. I would love to be able to direct the returning spacecraft to a point on the map that allows us to land it without having to recover it from an unknown place in the desert.

Supersonic Aircraft SpikeThe picture at the top of page is where we started. I expect that the spike will not be on the spacecraft and it is also now unlikely to be on the transonic test vehicle, but it is important to understand why we see them on supersonic craft. Sometimes a very long sharp nose can also produce the desired effect.

The picture at right is a NASA test vehicle with a spike. There are many supersonic aircraft that either have a spike of a very sharp nose well ahead of the wings. Why? We discuss this after the following paragraph.

Returning from space the spike would be a liability in the heat of reentry. It will also not be an asset in slowing down a craft. We only need to have the spike as an option to help lower the Resistance to breaking the sound barrier for our tests. At the time of posting, Jason has gotten rid of the spike and opted for wings tucked back behind the shock wave.

In our tests we will use gravity to accelerate the test craft to way past the speed of sound, but shock waves (pressure waves) would slow us down and limit our top speed. We would probably still break the sound barrier dropping the craft from around 40km altitude, but the quicker we transit the sound barrier the higher our top speed and the better the results from our experiment.

So What Does the Spike Do?

supersonic shockwaves in a windtunnelAs I said a sharp nose is the same as a spike and the image to the left shows the effect of the nose/spike as it moves the shock wave to a point well ahead of the main body of the craft and away from the wings. A sharp point is a very low area of shock and in the image you can see the shock waves from the wings as very low level compared to the shock from the tiny front of the aircraft. So long as the wings are tucked in behind the initial shock wave than the drag is lowered considerably. The reason that it was so hard to break the sound barrier was simple. The craft used had their wings in the high drag area caused by shock waves.

Now I may have been a bit simplistic here, but none the less, the spike is important to supersonic flight. Since we are wanting to slow down in Phase 2 tests returning from space via a sounding rocket, we can actually round the nose of the returning spacecraft and still get the supersonic shock to clear the wings

So Why Didn’t the Shuttle Need a Spike?

WPointy nose and shockwaves at mach 6.ell it did need to slow down and so you might think that a blunt nose is a good thing to create drag, but that is not the reason. Wouldn’t a sharp nose be good for takeoff, spike or no spike? Well, in some ways, yes, but the shuttle had wings that were very wide and a spike could not be placed that far forward. The resulting shock waves on takeoff and especially re-entry would be a bit problem as they would hit the wings.

Re-entry would be the biggest problem. The shock wave from a sharp nose would hit the wings and further heat the air. You would be adding thousands of degrees to the heat that it is already being generated on the leading edge of the wing – not a good idea! See the image above right. This would be a poor design for such a craft. The image shows a pointy nose model in a mach 6 airstream. You can see the shock waves hitting the wings midway along their leading edge.

So What Happens with a Blunt Nose?

The image to the right says it all. The blunt nose acts as a ram and pushes the shock wave way to the sides. This misses the wings by a long way – and the tail of course. The blunt nose does add to drag so that is another benefit to slowing down, but a minor one. It is the additional heat caused by the shock wave over the wings during re-entry  that had to be eliminated

What Else Protected the Shuttle from Shock?

Ever consider the orange main fuel tank? Where was the shuttle positioned relative to its nose. It had a point, but was really broad.

What effect did that have during launch at high speeds. The shock wave that resulted missed the shuttle entirely. It is important that the top of this tank was far enough forward to protect the shuttle. The whole design and shape of the combined modules on the launch vehicle was super critical and not just a random bunch of sizes. Minimizing shock waves means being able to both protect the vehicle and increase the payload as you have less drag.

In other words, if the main tank had needed less fuel and had been smaller, then it would still have needed to be as high to push the shock waves aside.

Each and every part of an aircraft that changes its size or sticks out causes shock. You must account for it or suffer the consequences.

The image at right clearly shows the shock wave of the jet disturbing the water. You do not have to be traveling at supersonic speeds to produce shock waves, but the faster you go, the more power is lost and the stronger the shock wave.

Aircraft Design Changes

ThunderStruck mk2ThunderStruck Design on the “Fly”

We now have 2 major changes to the ThunderStruck aircraft. The first is shown in the image to the right. Winglets. The second is a square-ish cross-section to the fuselage rather than a round fuselage – this is under consideration to aid in landing the craft.

The image to the right still shows the aircraft with a round fuselage, but it is obvious that we will miss out on some lifting ability from the body at landing by making the fuselage round. A flat surface on the underside if the craft will provide more lift at the right angle of attack.

winglet_effect_Winglets

The image right is from Wikipedia:

Line drawing of wingtip vortices behind a conventional wingtip (on the left) and a blended winglet (on the right).

This is important as it reduced the vortices behind aircraft that cause so many dangerous incidents at airports when aircraft get too close to each other. It also reduced drag and thus efficiency in aircraft.

The ThunderStruck craft will certainly use the winglets to reduce drag by reducing vorticies, but this will have no impact at supersonic speeds because we will be using symmetrical wing. Normal wings have a flat bottom and a rising leading edge and a trailing edge on the top surface.  This makes the air flow faster over the top compared to the steady flow over the bottom. This reduces the pressure on the top pushing the wings up. This would be nice for the cruising stage after the dive, but bad for holding the craft in a supersonic dive. Any air flow over any asymmetrical surfaces may produce drag or lift that could pull the craft out of a supersonic dive early. The effects could be catastrophic.

Many high altitude model aircraft dropped from high altitude balloons (usually illegally) follow a roller coaster ride due to the thin air and lift in the wings. We don’t want that so the wings will be symmetrical – no lift. We do not need them for the supersonic dive. What we also need is symmetry in the aircraft at any cross-section, vertical or horizontal. The closer to total symmetry, the more likely that ThunderStruck will reach speeds of near 2,000kph. So if we have winglets, they need to extend top and bottom.

So Why the Winglets?

Simply we need wheels. The winglets hide the wheels and any need to lower wheels for landing. We may use a retractable wheel for the front, but not the rear wheels.

The Winglets will also house twin rudders, making a dedicated rear stabiliser (top and bottom) unnecessary. The rear cross-section looks like the picture below:

ThunderStruck Cross-section

Lifting Body (at Landing).

In the cross-section above the flat surface of the lifting body is obvious. This will only be important when landing as the craft assumes a significant nose down attitude during the gliding phase. Since we have no lift from the wings, the craft needs strong elevators to redirect the airflow at the rear of the aircraft to keep control. We will stay aloft by having speed due to a high angle of attack (nose down). Large elevators will keep the aircraft flying at this high angle of attack. It will be a poor glider – but so was the space shuttle – for different reasons – more to do with the delta wing configuration. A round fuselage cross-section would not aid the lift of the craft at landing. A square fuselage will increase the drag as the surface area is greater, but it will help fly the craft at lower speed when landing. It will have little effect during the glide phase. We may add canards to the front of the craft to increase the lift at the front during low speed flight, but they will pop out after we go subsonic. Delta wing craft work well at supersonic speeds, but are poor performers at low speeds. In the picture at the top of screen, the craft does not have a supersonic spike. We will need this for the Transonic tests, but not for return from a sounding rocket or re-entry from orbit.

Below is a closer look at the Winglets. We have yet to show the square cross-section in an image, since this is still under test. It is felt that the flat surface will help drive a higher pressure under the craft (between the ground and the craft) allowing it to land at a slower speed. This is a form of “ground effect” making the need for a long runway important to drop off speed until the effect lessens and the aircraft eases to the runway. Tests may find little difference in the landing speed and thus we may revert to a cylindrical fuselage. Time for some wind tunnel testing.

ThunderStruck mk2 closeup

 

What is Project ThunderStruck?

ThunderStruck verticalProject ThunderStruck set to Break Barriers

by Robert Brand

This project is two projects in one. The total aim of ThunderStruck is to build as small a space craft as possible that will handle reentry, remain stable and land softly. The “softly” is important as commercially there are payloads that may need to be conducted in a “weightless” environment and then be brought down without too much jarring. A parachute landing will not be suitable. My son who is very aerospace savvy was keen to be involved in some way and Project ThunderStruck was born. We will help do the low altitude testing – when I say low, i mean from 40Km altitude (25 miles)

Imagine a time when a 12 year student could design and build a supersonic glider 2.5m / 8ft long, attach it to a huge helium or hydrogen balloon and take it to the edge of space, release it, fly it into a dive back to earth that will reach Mach 1.5 / 1,800kph / 1,120mph and land it. Well that time is now and the student is Jason Brand from Sydney Secondary College / Balmain Campus. He is in year 7 and has already broken plenty of records with his hobbies. Breaking the sound barrier will be another cool record.

New Science, New Data, New Opportunities

Apart from the glitz of the big event in 6 months (a 12-year-old breaking the sound barrier) there is a lot of science being done. In fact the event side of this project will be funded by sponsors and the crowd funding will be for the additional science outlined below.

There is a commercial opportunity to design and create a winged re-entry vehicle specifically for delicate payloads and experiments that last for more than 4 minutes in a weightless environment (tourist sounding flights to space). These are experiments and payloads that would find a parachute landing too harsh. There is a final output of the work and that is a spacecraft for experiments or even a payload taxi service back to earth. The most important aspect of this work is determining the smallest size of a winged spacecraft that can remain stable during re-entry. There are three stages of the physical testing:

  • Transonic – Project ThunderStruck in 6 months time
  • Reentry from space (delivered on a sounding rocket – no orbit); 2-3 years away.
  • Re-entry from orbit; 6 years away

There are two science components to the upcoming testing over the next 6 months:

  • Stability of a small aircraft at mach 1.5 / 1,800kph / 1,120mph and lower speeds for landing
  • testing a new type of surface for high-speed flight. (not a heat shield)

Since Jason has experience and a fantastic track record in High Altitude Balloon flights and flying remote control aircraft, he wanted to look after that first phase of the project. The transonic Phase. Transonic flight is the flight around the area of breaking the sound barrier. All sorts of problems occur near the sound barrier. When we drop the aircraft from 40Km altitude, first we have to get through the sound barrier as the drag increases significantly, but once through the barrier, the drag essentially reduces until your speed increases further. The real testing then commences as our tests will be about slowing, not increasing speed. We will be measuring the behaviour of the craft and airflow over the surfaces.

Project ThunderStruck has Commenced Flying Tests

Just in case you are concerned that this is all talk and no action, we started test flights in Sept 2014. The results are simply amazing and we will use them to refine our project.

The event will take 6 to 9 months to complete and the testing is the most important aspect of this project. It is new territory for us and almost the entire world. There is still fresh science to be done and innovative ways to use new materials and designs. Recently we learned a lot when a non-aerodynamic payload (space chicken from Clintons Toyota) reached speeds of 400kph / 250mph with its parachute deployed. This is because the air is pretty thin up at 33.33Km or 1/3 the way to space. Our payload took several measurements during the fall.

Rankins Springs Free Fall UpLift-19The space chicken was a simple test and we are now happy that we can easily fly at speeds of Mach 1.5 in the very thin air high up in the stratosphere. Left is a picture of the chicken falling back to earth at 400kph. Even the parachute could not slow the payload in the thin air. It slowed down as it reached 28Kms altitude and the air got a bit thicker.

We have started fund raising as we need help to cover the costs of the science parts of the project. Once we know what we have, we can decide on the extent of the program. We need $20,000 or more just for science and we have turned to crowd funding for that.

We have some “Perks” as part of crowd funding that I hope you will love. Some of our payloads will go supersonic before the big event, but they will not be aircraft. We might even donate one of our supersonic payloads to a generous contributor.

STEM – Project ThunderStruck set to Inspire Kids Worldwide.

Fighter jets break the sound barrier every day, but this radio controlled aircraft has no engine, weighs 9Kg (20lbs), is 2.5m (8 ft) long. So the pilot must be a really experience Top Gun to fly this plane at 1,800kph (1,120mph)? Well, no. His name is Jason Brand and he is 12 years old.

This is probably one of the most important demonstrations of STEM education that you can support. This is beyond the ability of almost every adult on the planet, yet a 12 year old student is set to inspire kids around the world with a daring project that is pure STEM – Science Technology Engineering Mathematics. It will make the seemingly impossible the domain of the young if they choose to break down the barriers imposed by themselves or others. Not only that, there is real science going on here.

Your Assistance is Essential

Your crowd funding help now is essential. It gets us started immediately. Flying balloons to the edge of space for testing is an expensive exercise and we have a 7 hour drive each way to get into areas of low air traffic away from the major aircraft trunk routes. We also have to buy a lot of radio systems to allow remote control from the ground when the glider is up to 100kms distance.

You can click on one of the 2 crowd funding links at the top right of the page. Even $1 will help unlock new discoveries and bed down older science.

Who is Jason Brand?

He is a 12 y/o student from Sydney Secondary College, Balmain Campus in Sydney, Australia.

He carried out his first High Altitude Balloon (HAB) project at age 9 and was so inspired that he sat for his amateur radio license at 9 years old. Since then he has launched a total of 19 HAB flights and recovered all 19. Some flights were in Croatia where mountains, swamps and landmines are risks not seen in Australia. He is also the Student Representative for Team Stellar – A Google Lunar X-Prize team attempting to get a rover onto the moon.

J20130414 Jason Brand on the Fuzzy Logic Science Showason appears on Radio and TV regularly and the picture right shows him talking about HAB flights on Canberra’s Fuzzy Logic Science Show in 2013. He is also a member of the Australian Air League, Riverwood Squadron. He plans to solo on his 15th birthday.

His father Robert Brand is an innovator in creating low cost solutions for spaceflight. He speaks regularly at international conferences, is a regular guest lecturer on aerospace at Sydney University, writes about aerospace and takes a very “hands on” approach to space. He supports Jason’s project fully.

How will ThunderStruck work?

The same way that the first pilots broke the sound barrier: in a steep dive. The problem is that since there is no engine and the biggest issue is air resistance, Jason will launch the aircraft from over 40km altitude or nearly half way to space! He will get it there on a high altitude balloon. The air is very thin at that altitude and the craft should accelerate past the speed of sound before it is thick enough to slow it down. A tiny fraction of one percent of the air at sea level. During the dive, the craft will accelerate to well over Mach 1 and way less than Mach 2 and will need to be controllable by its normal control surfaces to pass as an aircraft. As the air thickens at low altitudes, the craft will slow and with the application of air brakes will slow and then be levelel off for normal flight to the ground.

The Technology

We will have a camera in the nose of the aircraft and it will transmit TV images to the pilot on the ground. Jason will be either in a darkened room with a monitor or wearing goggles allowing him to see the view from the on-board camera. This provides what is known as First-person Point of View (FPV). The aircrafts instruments will be overlaid on the video signal. This is known as “On Screen Display” or OSD. Below is a view typical of what will be seen by Jason as he lands the craft.

osdThe video signal must travel over 100kms to be assured of the craft being in the radius of the equipments limits. Similarly we must send commands to the control surfaces of the radio controlled aircraft. Again this must work at a distance of over 100kms. The craft has ailerons, elevators and rudder as well as air-breaks and other systems that need controlling. We will use a 10 channel system to ensure that we have full control of every aspect of the craft and a “binding” system will ensure that only we can fly the aircraft.

We will have to buy 2 x $5,000 GPS unit capable of sampling at what is essentially the speed of a missile. These are highly restricted items, but essential. The unit will record to an SD card and send back telemetry every second. It is essential to know the speed during the flight rather than waiting until after the event. After all Jason needs to knowthe speed to be able to fly the aircraft. We will also need 2 x radar responders to allow other aircraft and air traffic controllers to know where our craft is and our balloon is at any time.

The Big Event

We can expect global TV News coverage of the event and many records to be broken. The day will start by filling a large Zero Pressure Balloon like the one pictured below.

OLYMPUS DIGITAL CAMERAThe balloon will carry the aircraft to over 40km where it will be released and go into a steep dive and break the sound barrier. As the air thickens, the speed will slow and the craft will be pulled out of the dive and leveled off to drop speed. The aircraft will eventually land and data and video records will be recovered. We will already know the top speed, but there is nothing like solid data rather than radio telemetry that may miss the odd data packet. Both the balloon and the aircraft will be transmitting live video.

There will be opportunities to attend, but it is likely to be in a rather remote part of the state (NSW, Australia) or a nearby state. The flight will be broadcast over the Internet and the opportunity to track and follow the flight will be available to all. The chance to be involved is high and the science and inspiration will be out of this world. Project ThunderStruck is set to thrill.

Visit our sister site wotzup.com for more space and balloon stories

Breaking Mach 1, but by How Much?

A Zero Pressure Balloon fill_2610Hitting the Mach.

by Robert Brand

The aim of Project ThunderStruck is hitting Mach 1 and a bit more for good measure. Basically breaking the sound barrier. We may reach Mach 1.5, but that will be very much related to the height we reach with the balloon and few other factors. Project ThunderStruck is about Breaking Mach 1 – anything faster is a bonus.

ThunderStruck will rise to 40Km or more for its record attempt. It will need to use a Zero Pressure Balloon capable of reaching 40Km plus carrying a payload in the region of 20Kg including cameras and electronics on the Balloon.

Thanks to http://hypertextbook.com/facts/JianHuang.shtml for the information below regarding Joe Kittinger’s Record Jump in 1960:

Captain Kittinger’s 1960 report in National Geographic said that he was in free fall from 102,800 (31.333Km) to 96,000 feet (29.26Km) and then experienced no noticeable change in acceleration for an additional 6,000 feet (1.83Km) despite having deployed his stabilization chute.

The article then goes on the mention that he achieved 9/10ths the speed of sound and continued to suggest (with maths) that he would have broken the speed of sound with an additional 1,300 m (4,200 feet) of free fall.

If we assume an average acceleration of 9.70 m/s2, it is a simple matter to determine the altitude at which a skydiver starting at 40 km would break the sound barrier.

 maths to calculate altitude at which the sound barrier is broken

That’s an altitude of about 116,000 feet or 35.36Km. So how fast might we go starting at 40km altitude?

maths to calculate the max speed from altitude

Sorry if the equations are difficult to see – that is the quality from the website.

This is nearly 200 m/s faster than the local speed of sound. At the incredible speeds we’re dealing with, air resistance can not be ignored. A maximum of Mach 1.3 seems very reasonable for a human in a pressure suit compared to the prediction of Mach 1.6.

Given that the altitude of the glider release will be 40Km or more, then a top speed of near Mach 1.5 is possible. If we go higher, then we go faster.

Why is ThunderStruck an Aircraft?

Why is it considered an aircraft if it is in free fall with little to no drag? Simply because it is designed to use the little airflow to stabilise itself. Like and aircraft at lower heights uses its control surfaces for stable flight, ThunderStruck does the same. As you might remember from the jumps in the past by Joe Kittinger and Felix Baumgartner, they had serious trouble controlling spin. ThunderStruck will use the exceedingly thin air to control the spin and other forces acting on the craft during its record breaking dive.

After the dive and breaking the sound barrier, ThunderStruck will pull out of the dive under the control of RC pilot Jason Brand (12 years old) and level off, washing off excess speed. It will then fly to the ground under manual control to land just like any other aircraft.

This piece on Felix Baumgartner from Wikipedia:

203px-Felix_Baumgartner_2013Felix Baumgartner; born 20 April 1969, is an Austrian skydiver, daredevil and BASE jumper. He set the world record for skydiving an estimated 39 kilometres (24 mi), reaching an estimated speed of 1,357.64 km/h (843.6 mph), or Mach 1.25, on 14 October 2012, and became the first person to break the sound barrier without vehicular power on his descent.

Baumgartner’s most recent project was Red Bull Stratos, in which he jumped to Earth from a helium balloon in the stratosphere on 14 October 2012. As part of this project, he set the altitude record for a manned balloon flight,[8] parachute jump from the highest altitude, and greatest free fall velocity

The launch was originally scheduled for 9 October 2012, but was aborted due to adverse weather conditions. Launch was rescheduled and the mission instead took place on 14 October 2012 when Baumgartner landed in eastern New Mexico after jumping from a world record 38,969.3 metres (127,852 feet and falling a record distance of 36,402.6 metres. On the basis of updated data, Baumgartner also set the record for the highest manned balloon flight (at the same height) and fastest speed of free fall at 1,357.64 km/h (843.6 mph), making him the first human to break the sound barrier outside a vehicle.

This piece on the Speed of Sound from Wikipedia:

The speed of sound is the distance traveled per unit of time by a sound wave propagating through an elastic medium. In dry air at 20 °C (68 °F), the speed of sound is 342 metres per second (1,122 ft/s). This is 1,233 kilometres per hour (666 kn; 766 mph), or about a kilometer in three seconds or a mile in five seconds.

The Speed of Sound changes with altitude, but surprisingly this is not due to density or pressure, but with temperature!

 Altitude vs temperature pressure densityDensity and pressure decrease smoothly with altitude, but temperature (red) does not. The speed of sound (blue) depends only on the complicated temperature variation at altitude and can be calculated from it, since isolated density and pressure effects on sound speed cancel each other. Speed of sound increases with height in two regions of the stratosphere and thermosphere, due to heating effects in these regions.

You can click of the image  (left) to enlarge the image and see it with a white background! For the purposes of this flight, we will be using the speed of sound at sea level.

Will there be a Sonic Boom?

Yes, but it will not likely to be heard. In fact there will be two. One as it breaks the sound barrier and goes supersonic and one again as it slows to subsonic. Givent he size of the craft and the distance and thin atmosphere, it is unlikely to be heard from the ground.