Fuels for Space Flight

Handling Hypergolic_Fuel_for_MESSENGER spacecraftFuel for Thought.

by Robert Brand. Fools and Fuel. It is the one thing that you can’t avoid and possibly the biggest risk to spaceflight. Fuel.

ThunderStruck will start with the premise that we are going to use the safest fuels and the greenest where ever possible.

Since we are initially talking about booster capability, we are looking at solid fuels and for safety, we will also not use hypergolic fuels as they are very dangerous.

This excerpt from Wikipedia:
https://en.wikipedia.org/wiki/Hypergolic_propellant

A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other.

The two propellant components usually consist of a fuel and an oxidizer. Although commonly used hypergolic propellants are difficult to handle because of their extreme toxicity and/or corrosiveness, they can be stored as liquids at room temperature and hypergolic engines are easy to ignite reliably and repeatedly.

In contemporary usage, the terms “hypergol” or “hypergolic propellant” usually mean the most common such propellant combination, dinitrogen tetroxide plus hydrazine and/or its relatives monomethylhydrazine and unsymmetrical dimethylhydrazine

Our booster will have a mass of about 2500Kg to 3,000Kg with fuel and the fuel will be about 2/3rds of the mass.

Below is a list of most common space fuels in use today. Please look up any words that you don’t understand.

We will discuss the Specific Impulse and Density Impulse more in a later post.

Specific Impulse:

Wikipedia:    https://en.wikipedia.org/wiki/Specific_impulse

Specific impulse (usually abbreviated Isp) is a measure of the efficiency of rocket and jet engines. By definition, it is the total impulse (or change in momentum) delivered per unit of propellant consumed and is dimensionally equivalent to the generated thrust divided by the propellant flow rate. If mass (kilogram or slug) is used as the unit of propellant, then specific impulse has units of velocity. If weight (newton or pound) is used instead, then specific impulse has units of time (seconds). Multiplying flow rate by the standard gravity (g0) before dividing it into the thrust, converts specific impulse from the mass basis to the weight basis.

A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently in creating forward thrust, and in the case of a rocket, less propellant needed for a given delta-v, per the Tsiolkovsky rocket equation. In rockets, this means the engine is more efficient at gaining altitude, distance, and velocity. This is because if an engine burns the propellant faster, the rocket has less mass for a longer period of time, which makes better use of the total force times time that was acquired from the propellant. This is much less of a consideration in jet engines that employ wings and outside air for combustion to carry payloads that are much heavier than the propellant.

Density Impulse:

https://www.quora.com/What-is-density-impulse-and-why-do-propellants-with-higher-densities-have-higher-density-impulses

Impulse density is a way of measuring the performance of different propellants regardless of their density. It’s a measure of how much force per time (impulse) you’ll get from a given volume of propellant. Higher density fuels have a higher Impulse Density because Impulse density is basically the propellants Specific Impulse multiplied by it’s density.

As comparison Lox-Butane and Lox-Methane both have a specific impulse of 365s, but the average density of Lox-Butane (at 1000psi) is 890.62kg/m3 while Lox-Methane is 823.34kg/m3. So Lox-Butane’s Impulse Density = 890.62 * 365 = 325076.3Kg-f-s/m3 and Lox-Methane = 300519.1Kg-f-s/m3.

This basically means that per Kg of Lox-Methane you’ll get the same Isp as Lox-Butane, but Lox-Butane can be stored in a smaller tank.

ROCKET PROPELLANT PERFORMANCE
Combustion chamber pressure, Pc = 68 atm (1000 PSI) … Nozzle exit pressure, Pe = 1 atm
Oxidizer Fuel Hypergolic Mixture Ratio Specific Impulse
(s, sea level)
Density Impulse
(kg-s/l, S.L.)
Liquid Oxygen Liquid Hydrogen No 5 381 124
Liquid Methane No 2.77 299 235
Ethanol + 25% water No 1.29 269 264
Kerosene No 2.29 289 294
Hydrazine No 0.74 303 321
MMH No 1.15 300 298
UDMH No 1.38 297 286
50-50 No 1.06 300 300
Liquid Fluorine Liquid Hydrogen Yes 6 400 155
Hydrazine Yes 1.82 338 432
FLOX-70 Kerosene Yes 3.8 320 385
Nitrogen Tetroxide Kerosene No 3.53 267 330
Hydrazine Yes 1.08 286 342
MMH Yes 1.73 280 325
UDMH Yes 2.1 277 316
50-50 Yes 1.59 280 326
Red-Fuming Nitric Acid (14% N2O4) Kerosene No 4.42 256 335
Hydrazine Yes 1.28 276 341
MMH Yes 2.13 269 328
UDMH Yes 2.6 266 321
50-50 Yes 1.94 270 329
Hydrogen Peroxide (85% concentration) Kerosene No 7.84 258 324
Hydrazine Yes 2.15 269 328
Nitrous Oxide HTPB (solid) No 6.48 248 290
Chlorine Pentafluoride Hydrazine Yes 2.12 297 439
Ammonium Perchlorate (solid) Aluminum + HTPB (a) No 2.12 277 474
Aluminum + PBAN (b) No 2.33 277 476

More discussion on fuels in a future post and we will explain our initial choice of booster propellant. The results of an explosion can ruin a flight or kill people. Safety is the big issue. More on that too in a later post.

aptopix india rocket fuel explosion

BOR-4 breakdown

ThunderStruck Spacecraft Development Begins

BOR-4 breakdownWinged Spacecraft Takes Form

Our Australian ThunderStruck team has commenced design of the ThunderStruck Spacecraft. This graphic (right), courtesy of Project Thunderstruck team member David Galea, is just a doodle to break down the benefits of the USSR BOR-4 design. Yes, we started with a 50 year old design and have worked our way forward as the basic air frame is a solid design that has a good flight track record. We then looked at Dream Chaser which looks surprisingly similar, but with a modern interior. We too will have a similar design to both of these but with some big differences. Our starting length will be 3m (10 feet); our unfueled mass is expected to be 400Kg and optimum payload return will be 50Kg. It will have hypergolic fuel for the space flight – main thrust and hypergolic thrusters. If our air-frame can’t support the mass, then we will increase the lift or size. The fuels under consideration are not like the very dangerous Hydrazine used extensively for most NASA missions, but much safer fuels that are pretty safe for humans. They often don’t pack the punch of Hydrazine, but safety is our biggest goal so long as the thrust is powerful enough to do the job.

This from Wikipedia: https://en.m.wikipedia.org/wiki/Hypergolic_propellant

A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other.

The two propellant components usually consist of a fuel and an oxidizer. Although commonly used hypergolic propellants are difficult to handle because of their extreme toxicity and/or corrosiveness, they can be stored as liquids at room temperature and hypergolic engines are easy to ignite reliably and repeatedly.

We are now go for liftoff in eerrhhhh …in 6 years… But we have started. We are choosing a suitable fuel at this time – one that is relatively safe for humans and still able to provide the thrust needed to de-orbit and maneuver. There are new fuels – not as powerfully as many of the well known thruster fuels, but sacrificing power for safety could be a really good thing if the numbers stack up.

Our Invasion of Space has Begun.

Let’s rewind a bit. ThunderStruck is a Spacecraft under development. This story is about our spacecraft that we are building for actual flight many years from now. We also have a transonic test vehicle that has yet to fly, but we hope early next year we will get permission to fly the craft in northern Queensland (QLD) – probably a little North East of Longreach, QLD. There may be more test vehicles and even the design of our spacecraft may end up radically different from our

At this time, the Thunderstruck transonic test vehicle has been on hold, but it too will benefit from the spacecraft design kicking off since they may share common components. The Spacecraft will be slow to design and build compared to the transonic testing flier, but we have to start this if we are to finish it in a timely fashion. So back to our spacecraft design.

It is expected that we will partner with a university that will assist with the build. At this time we are closest to Sydney University and we know that they have similar goals of working with a winged re-entry flier.

It is clear that we are not relying on using the Russian BOR-4 as a blueprint, but it is a starting point. It is also clear that the BOR-4 and the Sierra Nevada Corporation’s Dream Chaser share a lot of common air frame characteristics. So Dream Chaser was the next craft to go under the microscope.

Critical to the design and thus one of the first components to understand is the type of fuel that will be needed. This may determine that we need a bigger craft to carry the tanks or that the shape must be different to handle the large tanks.

Dream Chaser Graphic on top of a Rocket for LaunchDream Chaser (pictured right) is large and has a crew. Our craft does not have a crew and the ThunderStruck spacecraft is small in comparison.

Dream Chaser can launch on top of a rocket and we expect ThunderStruck to do the same. ThunderStruck is way smaller and potentially has folding wings and thus could sit inside a fairing making the ride more comfortable.

ThunderStruck will have a docking ring and the ability to swap old and new payload canisters. ie to provide a new empty canister to , say, an asteroid service craft and bring back a full set of samples.

ThunderStruck will evolve and its capabilities will change as we grow. Our aim is to make the smallest rocket launched spacecraft with wings for re-entry and an exchangeable payload.

 

2022 Mars Delta-V Requirements

Navigation – Earth to Mars Delta V

by Tim Blaxland – Introduction by Robert Brand

I have not yet introduced you to our Navigation chief Tim Blaxland and I will do that soon enough. Let us just say that he knows his stuff. When I was requested to make Mars the destination of the first shakedown flight of the ion engine equipped ThunderStruck craft in 2022, here was his initial response. This may go over a few heads, but it may be important for you to know that we have the ability to actually do the work required. What we don’t know about building and operating a spacecraft will be firmly supported by the right staff with the right experience and credentials – when the time comes. Until then, please understand that we are a capable team and soon to become a space sector company. I hope that you find this email interesting. I will post some orbital pictures when we have them ready for publication in a week or so..

The importance of this work was to ensure that 2022 provided a window of opportunity to leave for Mars. Here is Tim’s email:

Robert,

These graphs show the arrival, departure and total delta-V requirements for Hohmann-type Earth-Mars transfers. Delta-V is displayed by colour, the horizontal axis is departure date (range Jan 2020 to Feb 2025) and the vertical axis is flight time (range 100 days to 500 days).

I know these aren’t what you were looking for, but they are relatively easy to produce and are moderately interesting. They are based on a simplified calculation method using instantaneous changes in velocity for Earth escape and Mars capture and do not consider things like ion engines which can be used to lower the departure and capture delta-Vs.

At least they give you a useful ballpark approximation of when the available launch windows are.

You’ll notice that there are two lobes to each patch. The lower lobe is the one typically used for conventional chemical rockets because they give a much lower flight time (7-9 months) without too much delta-V penalty. The associated transfer orbit does however have a relatively high eccentricity. They top lobes have longer transfer times but lower eccentricity and I believe they will give us greater opportunity to maximise the use of the ion engines but I need to do more research in this area.

Earth to Mars Delta V:

Arrival delta-V (the cross-hairs are on the minimum for 2022 – 29th July 2022 with a flight time of 321 days)

Arrival delta-V (the cross-hairs are on the minimum for 2022 – 29th July 2022 with a flight time of 321 days)

Departure delta-V (the cross-hairs are on the minimum for 2022 – 17th September 2022 with a flight time of 387 days)

Departure delta-V (the cross-hairs are on the minimum for 2022 – 17th September 2022 with a flight time of 387 days)

Total delta-V (the cross-hairs are on the minimum for 2022 – 28th August 2022 with a flight time of 347 days)

Total delta-V (the cross-hairs are on the minimum for 2022 – 28th August 2022 with a flight time of 347 days)

Tim will be giving me a better breakdown of the navigation profiles, but 2022 is such a long way and we may slip or gain over the years, so it will be little more than an exercise to ensure we understand the time taken with an ion engine and the problems that may arise. I look forward to more detail soon and I will share it with you.

Press Release 3 – Mars Mission

mars-atmospherePress Release – Mars Mission

Monday 9th Feb 2015

Release Date: IMMEDIATE

2022 Australian Mission to Mars

Sydney, NSW, Australia.

Project ThunderStruck is the brainchild of Australian aerospace entrepreneur Robert Brand. The spacecraft is in its design and testing phase and will be capable of taking many forms with its modular construction. The unmanned ThunderStruck craft is expected to go into commercial production in 2021 and embark on a shakedown flight to Mars in 2022. a new craft is assembled for each mission. The choice of rocket will be made closer to the date.

The Mars shakedown cruise will be a public demonstration of the vehicle’s systems and its ion engine for commercial spaceflight. The group expects ThunderStruck to fly away from earth, taking pictures of the moon and earth together and then on to Mars. The flight to Mars will take much longer than the flight of the Curiosity rover and other such craft as the ion engine only puts out continuous low level thrust. It will need to loop around Mars many times while it brakes before settling into a low orbit where it can deploy or conduct the experiments on board. This will take a couple of years to complete, but it will be the first private mission to Mars. The exact time it will take will be dependent on the final mass of the vehicle, the power of the launch vehicle, the power of the ion engine and the position of Mars relative to Earth.

The vehicle will use new technology, much of which will be developed in Australia. The cost of the new technology will be significantly lower than current government funded systems and a very inexpensive alternative to building your own components for your spacecraft as many of the features needed will already exist.

The Space Courier Service

Brand is not looking to sell the craft for others to use, but to provide a service to deliver payloads or return them to earth. In what has become know as a Triple Play, He wants his company to provide the vehicle, communications and the mission control for the flight, leaving the customer to simply look after their experiment or cargo once delivered. Where the concept of taking astronauts to the International Space Station has become known as the “Space Taxi” service Brand has called ThunderStruck the workhorse of the “Space Courier” service.

One possible use of the craft is for sample returns for the asteroid miners. ThunderStruck would rendezvous with the survey vehicle near an asteroid and provide an empty payload container and bring back 50Kg of samples in a full container. Depending on the chosen configuration, Thunderstruck will return the sample to Earth via a capsule and parachute or via a winged re-entry and landing on Earth. The ideal place to land will be in southern central Australia if it is a capsule and potentially a runway closer to civilisation if a winged vehicle. We are looking to the likes of Spaceport Australia to provide those facilities.

Other services could include taking small satellites to an area of space for release and then relaying the data back to earth. Taking an experiment to a site and being permanently part of the experiments  control system until end of life. Even the International Space Station (ISS) could have a version strapped to the outside and upon release it could land within a day with a crucial sample. With the winged version believed to be only 3m to 5m long, the crafts systems can be dormant for years and be made ready for flight at the flick of a switch. With a non-volatile/inert chemical thrust system, there is no danger to the space station being left on the outside.

One potential experiment for the Mars shakedown cruise is the release of many small cubesats, each with their own experiments. The ThunderStruck craft would remain close by and act as a communications relay to earth for the experiments. They are small with little room for high powered communications or the energy it requires. Remaining close by allows the high power transmitters aboard ThunderStruck to relay the data back to earth.

Depending on the remaining fuel for the ion engines following the Mars encounter, it may be possible to fly elsewhere in the solar system and do some rudimentary science or obit the sun taking observations. ThunderStruck will have a camera on board and may be able to conduct further observations and science for many years to come. Similarly to the long time it took to settle into a low Mars orbit, it will take a long time to climb out of a low Mars orbit. The thrust from an ion engine would do well to disturb a piece of paper on you desk. Its continued use in space slowly adds momentum as space is essential free of friction.

ThunderStruck is set to revolutionise the Australian space sector and provide an extensive number of space related job. There is currently little work here in Australia for space graduates from University. They tend to leave and go over. We expect to change that. The project should work as a catalyst for other stalled projects. After all, without an Australian launch vehicle, we will be headed overseas for all launches. A local capability will be an obvious benefit and an obvious business to establish.

A core team of people is being assembled and business arrangements are being considered, but the Project has reached a critical mass that will see it through to commercialisation.

Read more at: http://projectthunderstruck.com

—————————–
PRESS CONTACT ONLY:   Robert Brand – contact@projectthunderstruck

Australia: 0448881101     Int’l:+61 448881101 – essential to leave a message if not answered.

Photos of Robert Brand on the Project ThunderStruck webpage are available for publication. Please do not use images of the craft as this is a supersonic phase 1 test vehicle and will NOT look like any of the final craft’s design UNLESS you label the images as such. Phase One testing is Scheduled for around July 2015 near Longreach in Queensland

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

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.