Trimming ThunderStruck for Speed

X2 shadow Trimming ThunderStruck Needs Extreme Knowledge

by Robert Brand

This post is very technical. I will try and make it a little easier to understand. I will not go into very deep into the various aspects that slow the craft, nor will I get into every aspect, just the major aspects that will cause us issues.

Designing a supersonic aircraft needs knowledge of supersonic aspects of airflow and pressure/shock waves. In a previous post we looked at the basic limiting factors and those important to getting us past Mach 1. This post will look at other factors that will cause us to make small changes to ThunderStruck to ensure we reach the maximum speed possible and get as close to Mach 1.5 as possible. We previously discussed the following:

  • Varying gravity due to altitude
  • The angle of the nose cone
  • The width of the fuselage
  • Altitude
  • Vehicle mass
  • Wing and Vehicle Drag Coefficient
  • Reference Area of the object in the direction of motion

In this post we will now look at other aspects of the design that will slow the crafts acceleration during its flight:

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

These factors take into account compressible air flows and incompressible air flows. Look them up, but simply Transonic and supersonic flows are compressible, subsonic flows are incompressible.  They are reflected in the items above.

If you would like to look at the Maths for these issues, there is a great document from Sydney University that can be viewed on the link below:

http://web.aeromech.usyd.edu.au/AERO2705/Resources/Research/Drag_Coefficient_Prediction.pdf

Base Drag

My knowledge here comes from rockets – same as the document. A flat based rocket does not have Base drag when it is firing its engines as the air flow does not have a pressure problem when compared to having a flat rear end! Below is a snapshot of the pressure differentials at the rear of the craft. There are more and bigger pressures not shown here, but you can clearly see the problem. as a rocket flies horizontally with its engines ignited, there is no void. The moment the engine ceases ignition, these pressure waves appear – Base Drag.

X2 Base Drag Pressure snapshot

Looks like a tapered fuselage at the rear of the craft is super important to acceleration towards the ground and again as the craft decelerates due to the thickening air density. It will need to taper from half way along the main wing part to the rear and go from 300mm to 50mm– enough for a parachute to be deployed – about 50mm. Whether we add a tapered cap, taking the final taper to a point for even less drag is not important at this stage. It will look better without the cap in drawings.

This important diagram from the linked document. This shows the flight of a rocket accelerating to Mach 1.6 (Dashed blue line) and then decelerating to to low speed (the solid black line). All the various drag issues are in this typical diagram. Base drag however is the difference between the two. There is no base drag during the rocket burn and then there is base drag once the engine ceases ignition.Drag issues in Transonic and Supersonic Flight

By gently tapering the fuselage to a point, we avoid disruption the boundary layer and any turbulence. For the X2 ThunderStruck flight the fall and acceleration will also look like the deceleration. Base drag will almost be eliminated.

Area Rule

We have spoken about this in an earlier post. That is keeping the cross-sectional area of the craft constant – so thinner where there is space (area) allocated to the wings. Area ruling will be somewhat addressed by the taper to the rear as discussed above in Base Drag. It is a fairly small effect unless you were spending significant time near the speed of sound. The X-2 ThunderStruck craft will spend 15 seconds between Mach 0.9 and Mach 1.2. I believe that it will be small and this is where the area rule has the biggest effect – but still small. There will be no additional change for area rule.

Transonic and Supersonic Wave Drag

The taper of the rear of the craft will minimise Wave Drag – both Transonic and Supersonic. Some playing with Wing Design may change the Wave Drag, but we will ignore it at this stage. I am not looking to play with the design unless there is a strong case. In the diagram above the Transonic Wave Drag begins at about Mach 0.9 and Mach 1.2 and Supersonic Wave Drag continues upward from that point.

Friction Drag

Friction drag occurs at low speeds with laminar flow being disrupted and the airflow becomes turbulent. We will have stalled at that stage and thus this is of no interest since we have an aircraft. We should have landed! This is ignored.

Trimming the Design

We have determined that we need to do two things. Stop the leading part of the winglets from protruding in front of where it joins the wing and to taper the fuselage. We will provide a picture of the new design shortly. Here is a render of the current X2 design without the new modifications:

X2 - Clouds2

The X2 ThunderStruck craft will have minimal impact regarding its maximum speed. I will reveal the new graphs shortly showing the speed at any given altitude point. As the air is extremely thin at our launch altitude, the increase in drag above 35km from the items above will not likely to be affect our top speed much as previously calculated, but may increase the deceleration slightly. That is the max G force as we slow. I will publish the updated results soon.

Finally a scan of the pressure waves from front to back on the X2 craft before we trim the craft:

X2 Pressure_Cut_Raised

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

Press Release 1

Jason recovering Payload Cameras gets his photo snapped

Jason recovering Payload Cameras gets his photo snapped. Robert Brand top right

Press Release 1 – 12 year old to Break the Sound Barrier

Thursday 9th Oct 2014

Release Date: IMMEDIATE

12 year old to Break the Sound Barrier

Sydney, NSW, Australia.

Jason Brand, 12 years old has commenced work on building a Remote Control Glider expected to reach Mach 1.5. He has worked with his father, well-known Space Entrepreneur, Robert Brand, on High Altitude Balloon launches since he was 9 years old. Coupled with his love of flying remote-controlled aircraft, Project ThunderStruck was born. Jason will use a massive high altitude balloon to take his glider to over 40km altitude (>25 miles) often called “the edge of space” and release it. The glider will dive through the extremely thin atmosphere and into the record books. It will be controlled from the ground via video and radio links and reach an expected top speed of around Mach 1.5 (1,800kph or 1,120mph).

Jason thought of the idea when his father was talking about a winged re-entry vehicle project that he has commenced. He was discussing the testing required at different stages of the flight and Jason realised that he could actually fly the tests for the transonic phase – the area around the breaking of the sound barrier.

Jason has been immersed in flying for many years. Since he and his father launched their first balloon when he was 9 years old. He was so inspired that he studied and passed his test to become a radio amateur operator (HAM) on his first attempt, again at age 9. 19 balloon launches later, they have maintained an unheard of 100% success in recovering their payloads. Jason flies radio controlled model aircraft, is a cadet in the Australian Air League (Riverwood Squadron) and is determined to solo at age 15. He has also be designing radio systems for long distance control and video. He will “see” from the cockpit camera via a video link and the instrumentation will be overlaid on the video. He will wear goggles and guide the aircraft through the dive, the leveling off at about 80,000 feet (24km / 15 miles) altitude. He will then fly the craft in for a landing.

Special tracking and GPS equipment will be required to verify the speed of the craft for the record books. Most GPS does not work above 60,000 ft and only special GPS systems will work near or above the speed of sound, like those used in missiles. Similarly the aircraft will carry a radar transponder that will advise other aircraft of the ThunderStruck aircraft diving at Mach 1.5. Even military aircraft do not get much over 80,000 ft and controlled airspace is below 60,000 ft. This will probably be the highest balloon and definitely the highest aircraft in the world that day.

This has never been done before and let alone by a 12 year old. It showcases STEM education (Science, Technology, Engineering and Maths) and the fabulous things that happen students are brought up to understand that most limits are there to be broken. Our motto is “New Heights and Breaking Barriers” and those include the Sound Barrier (1,233kph / 766 mph). Soon we will start our funding campaign as it will cost nearly $100,000 to make this a reality and we are looking for global support for such a spectacular event. On the day the event will be captured by cameras on the balloon, the aircraft and from the ground. These will be both live and also recorded. A live broadcast will be available on the Internet for the event scheduled for April 2015.

Website: http://projectthunderstruck.org

————————-

Contact:   Robert Brand – homepc@rbrand.com   Australia:  02 9789 2773    Int’l: +61 2 9789 2773

Photos of Jason and Robert Brand on the Project ThunderStruck webpage are available for publication as is the logo and the CAD images of the aircraft.  http://projectthunderstruck.org/media/

Jason Brand (12 y/o), creator, designer, builder and flier of ThunderStruck

  • HAM radio operator since he was 9 years old
  • First balloon launch and recovery at 9 years old
  • Member of the Australian Air League – Hornets Squadron, Riverwood, Sydney – Cadet
  • Flying Radio Controlled aircraft since 2013
  • Launched, tracked and recovered 19 High Altitude balloons and recovered 100% (all 19)
  • Attends Sydney Secondary College, Balmain Campus – Y7 in 2014
  • Is the Student Representative for Team Stellar – a Google Lunar X-Prize team headed for the moon.

 

Robert Brand: Leading Australian space entrepreneur, Senior Adviser for Team Stellar, ex-OTC staff member, amateur radio operator, Public Speaker on Innovation, Social Media and Space with a focus on Australian Space. Proud father of three amazing kids.

Worked on Apollo 11 equipment at 17 years old, supported Apollo missions, Voyager missions, Shuttle missions and ESA’s Giotto mission to Halleys Comet. Several times he was stationed at the Parkes Radio Telescope.

With his son Jason he has launched 19 high altitude balloon mission and recovered all 19 – two of them were in Croatia. He has designed a mechanism to turn a weather balloon into a zero pressure balloon during flight. Many of the balloon flight have been commercial flights for customers.

End Press Release.

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.

Our Aerospace Adviser Asks Questions.

Answering our Adviser’s Initial Questions.

Area_rule_unifilar_drawing.svg

Below is an exchange between our new adviser to the project (to be announced officially soon and myself (Robert Brand). Here are his initial comments and please remember that he has not seen anything yet. Our adviser is a pilot with an aerospace engineering degree.

Our Adviser  Hi Robert, Here are a few questions and thoughts.

1. Propulsion

At a first glance you may think you don’t have a propulsion problem, because the thing is falling down.

The fact is, you do. The basic forces and their components (lift, weight, thrust and drag) are always in balance as long as the aircraft is not accelerating in any axis.

This is valid the other way around as well: The aircraft will accelerate as long as the forces are not in balance.

For your case, you need to have the capability to accelerate beyond the sound barrier.

The problem is that the parasitic drag increases exponentially as you approach M=1 and because you are going at a certain angle towards the ground, a certain component of this force, or all of it if you dive vertically, adds to your lift. Once your lift becomes greater than your weight, you will start to slow down.

If this happens before M=1, you will never reach supersonic speed. If it happens after M=! you can further accelerate, because the drag drops after transonic. Transonic is the worst place to be. I order to be supersonic, you must achieve M=1 ASAP, before the air becomes dense.

If you drop from 33km, forget it, because at 30km you can already feel the effects of atmosphere.

The first thing you need to do is apply total surface design, or coke-bottling. The total surface of your craft must be consistent, so at the place where you have wings, your fuselage must be narrower. This dictates your fuselage to be in a shape of a coke bottle. This will reduce drag significantly.

Also, center of lift on the wings changes in supersonic flight and you need to cope with that. There are two strategies, variable wings or variable centre of gravity. I have a very original idea how to solve that.

2. Stability

Any object going through a fluid tends to assume a low drag position. Sometimes this low drag position means rotating and spinning.

You can solve this problem by active control (unless you have f-16 engineers on board, forget it) or aircraft design.

I would suggest delta wings, high swept. Delta wing has an inherent auto stability feature and high sweep angle to reduce drag and effect of the wings.

Accept it, your aircraft can be designed either for high speeds or low speeds, unless you have flaps or variable wing geometry.

———————

My Response

I look forward to how he views this and I will report back soon. I expect that I will have allayed most of his fears:

Firstly we are already applying the constant area rule. Even the A380 has aspects of the rule in the design. I lectured at Sydney Uni on the subject only a few weeks back. I understand the rule and some other rules to do with supersonic flight, although their effects are much less than the constant area rule.

Yes, the wings may very well be more swept back than in the image on the site. We will do drop tests to a certain the best wing shape and we have access to a wind tunnel.

The wings will be symmetrical (top and bottom)– ie zero lift. They will be therefore not an issue at supersonic speeds. The elevator will provide the “lift” with speed at lower altitudes. Yes, it will land “hot” – we may use “flaperons” ie combined flaps and ailerons. It should be noted that these are less effective as ailerons when they are biased down as flaps, but they will be bigger than needed. They will be symmetrical also. Flaperons are really ailerons  that are mixed with the flaps signal on the transmitter to bias them both “on” as flaps/ The ailerons do not work with the same efficiency when they are both biased down, but they do work. We may use separate flaps, we may not use flaps. Testing will determine the stability and best options.

Below is a video that shows how they mix the signals in the transmitter of radio controlled models to adjust the various control surfaces. This is a third party video

The spin will be counteracted by the large ailerons even in low air, the trick is to stop the spin in the first place by making the craft very symmetrical and test that aspect.

Our novel answer to controlling the need for different centres of gravity: We will have serious control of the centre of gravity in the craft and we will be able to move the batteries and electronics with a screw mechanism back and forward in the fuselage. This will keep the craft from being unstable at supersonic speeds. Once it goes back to subsonic, we will begin moving the centre of gravity back as we begin to level out the flight and slow the craft.

At slower speeds, we have air brakes that will slow the craft if needed

The supersonic spike at the front of the aircraft is used to create the shock wave with a pin point device ahead of the fuselage and ensure that the biggest part of the shock misses the wing entirely. A shock wave over the wing creates massive drag and this is why many pilots in the early days, tried to break the sound barrier and failed. The spike doubles as a VHF / UHF antenna

Three weeks ago we launched a payload mainly of wood, covered in bubble wrap for the electronics and, with the parachute deployed, it reached 400kph. For the event we will be using a Zero Pressure Balloon to get to over 40Km altitude. If the 9Kg of the payload are not enough, we will increase the weight and size of the craft. We will break the sound barrier, but need to show it is a fully working aircraft after the dive.

In World War II bombs from high altitude aircraft regularly broke the sound barrier. We will shift the centre of gravity well forward and act like a bomb. We should be able to punch through that barrier with a lot to spare – even Felix Baumgartner broke he sound barrier for his jump altitude of 39Km. He was not very aerodynamic. We expect to terminate supersonic flight at around 31Km

Yes, transonic is a bad place. We do not intend to allow the craft to stay there! Punch through while the air is super thin and keep accelerating!

Will we make Mach 1.5? – it depends on our launch altitude. We will achieve Mach 1 – the sea level speed of sound is our target. About 1200kph.

Area_rule_unifilar_drawing.svgThere is much more, but I expect that I have answered most of your questions in this email. We will be using ITAR controlled GPS units for supersonic tracking and also we will be using radar transponders to warn other aircraft. The Jason and I will be testing a lot of aspects of the flight with drop tests from balloons. I will be launching another balloon in a week’s time.

The picture above shows the constant area rule – efficiency is gained by the cross-sectional area of the aircraft being constant along its length. The fuselage gets thinner where the wings are as there area has to be accounted for. This rule is important as aircraft get close to the sound barrier and this is why Boeing 747 aircraft were so efficient.

Note the light blue area has to be the same as the dark blue area, including the area of the wings. This is the “coke bottle” shape that our adviser mentioned – note the thinner mid section of the central body.