̽��ֱ�� of Cambridge - rocket

Graphene heads to the moon

sc604 — Wed, 30 Nov 2022 15:35:21 +0000

Cambridge researchers are part of a European project testing graphene’s ability to protect spacecraft against the sticky, sharp dust on the moon’s surface – a challenge for lunar missions since the Apollo era.

Opinion: How to launch a rocket into space … and then land it on a ship at sea

Anonymous — Wed, 13 Apr 2016 14:42:18 +0000

On Friday 8 April 2016, SpaceX’s Falcon 9 rocket launched a mission to deliver a spacecraft called Dragon with its payload of supplies and experiments into a trajectory towards the International Space Station (ISS). Most remarkably, the first-stage booster then landed on a ship.

This is no easy task. Think back to 1969 when the Apollo 11 mission delivered three astronauts to the moon. Neil Armstrong and Buzz Aldrin walked on the moon while Michael Collins piloted the command module in lunar orbit. All three returned safely to Earth.

̽��ֱ��first stage of the huge Saturn V rocket that launched them into space burned for about three minutes and then crashed into the ocean. ̽��ֱ��second stage burned for a further six minutes, taking the craft into near-Earth orbit. It too was jettisoned and then burned up during its descent to Earth. ̽��ֱ��third stage burned for nine more minutes to send the astronauts towards the moon – again burning up on re-entry. ̽��ֱ��Saturn V rocket, at a cost of US$6 billion in 1969, was completely lost.

On the astronauts' return, only the command module splashed down in the Pacific Ocean. Of the 140 tonnes of metal that were launched, only five tonnes returned to earth. And at launch, the mission carried a staggering 3,000 tonnes of fuel … more on this later. Just imagine the cost saving if the Saturn V had been able to return to Earth almost intact – and then land itself to be used on another mission. Well, as the latest SpaceX landing proves – along with the reusable technology being developed by Blue Origin – that dream is becoming reality.

Of course, there have been reusable spacecraft before. ̽��ֱ��space shuttle was intended as a reusable spacecraft. ̽��ֱ��orbiter returned to Earth landing like a conventional aircraft, and the two solid rocket boosters could be recovered from the sea. Only the huge orange external tank would burn up, but getting the spacecraft ready for the next flight was slow and expensive.

̽��ֱ��SpaceX philosophy is that the majority of the rocket can be rapidly recovered, refuelled and reflown, making for significant cost savings. Fuel is less than half a percent of the cost of the mission, so there is potential to decrease the cost of getting to space dramatically.

̽��ֱ��rocket science bit

But what of the rocket science? Well, the ISS is in “near-Earth orbit”, at an altitude of about 400km. This is less than the distance from London to Paris, albeit straight up. It is orbiting at a speed of about 7.7km/s – it only takes about 90 minutes to go once around the Earth.

So how much energy does it take to deliver 1kg of payload to the ISS? First, think of kinetic energy (KE) – yes, you learned this at school. At 7.7km/s, the KE per kilogram works out at about 30MJ (megajoules). But you also need to consider gravitational potential energy (GPE) – yes, you did this at school, too. ̽��ֱ��force of the Earth’s gravity doesn’t change very much over this short distance upwards given that the Earth’s radius is 6,400km. So it’s easy to work out that the GPE needed to lift 1kg up to 400km is only about 4MJ. This is small compared with the 30MJ of KE required.

But not only do you need to get your payload to 7.7km/s, you have to carry the fuel in your tanks as well. Thanks to Konstantin Tsiolkovsky’s “ideal rocket equation”, however, we know that liquid fuels, which have a faster gas jet speed, are more efficient than solid fuels. Essentially, by using liquid fuel, each 1kg of payload needs a minimum of 4.5kg of fuel to reach a speed of 7.7km/s, while with solid fuel, you’d need more than 20kg – and this is before taking the rocket mass into account. This is a very good reason why rocketeers, including SpaceX, prefer to use liquid fuels; with a high gas jet speed, the launch mass is much less.

̽��ֱ��secret of SpaceX

So how does SpaceX’s rocket work? ̽��ֱ��Falcon 9 is a two-stage launch vehicle. Each stage uses a liquid fuel with liquid oxygen (very similar to the kerosene and liquid oxygen fuel used in the Saturn V – chemistry hasn’t changed in 50 years). Falcon 9’s first stage “booster” is by far the largest and most expensive component of the launch mass and it makes sense to try to recover it for reuse – it’s no good to have it splash into the sea because the resulting damage and corrosion would render it useless.

And so SpaceX has developed the Falcon 9 booster so that it can land on a ship. ̽��ֱ��idea is that shortly after main engine cutoff and stage separation, the booster flips over and directs itself towards an unmanned drone ship that is waiting as a landing pad.

During its descent, the booster reaches speeds of around 1,000m/s (double this after more adventurous geostationary missions) but its fins and engines control the speed and direction of the Falcon, slowing it down as it approaches the Earth. At the last minute, four legs then deploy – and it makes a soft landing at a speed of less than 6m/s. All of this delicate navigation is performed by onboard computers and inertial navigation systems. ̽��ֱ��landing is so fast that no human could react quickly enough to ensure a smooth touchdown.

To make things trickier, the ship is pitching, rolling and heaving in the sea. It’s hard enough for pilots to land on an aircraft carrier – Falcon is a tall slender column some 20 storeys high. Once the Falcon has landed, the legs lock out rigidly. In one of the earlier Falcon missions, one of the legs failed so even though the landing was a success the Falcon fell over shortly after, resulting in a huge conflagration. But that’s why they use an unmanned drone ship as a landing platform – no-one gets hurt. Of course, it’s easier to land on land – and the Falcon does this if the mission flies over land. But the ability to land at sea adds flexibility.

What next?

Falcon 9 and Dragon are paving the way for a new generation of low-cost reusable spacecraft – and SpaceX is already developing Dragon to launch and return up to seven astronauts into orbit and beyond. Perhaps next, there’ll be a refuelling base on the moon? Then Mars is an awful lot closer.

̽��ֱ��flexibility offered by reusable vehicles is the stuff of science fiction – the classic movie Star Wars and more recently Martian and Interstellar are nothing without space ships that launch at the push of a button. We’re not there yet, but with spacecraft that can hop around like aircraft, then anything is possible.

̽��ֱ��author wrote this piece with the assistance of one of his former Trinity students, Lars Blackmore, who now works for SpaceX as Principal Rocket Landing Engineer. Lars graduated with his MEng from Cambridge in 2003 and a PhD from MIT in 2007. He is now responsible for landing Falcon 9.

Hugh Hunt, Reader in Engineering Dynamics and Vibration, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

Hugh Hunt (Department of Engineering) discusses the intricacies of reusable spacecraft.

SpaceX

SpaceX’s Falcon 9 rocket blasts off

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Your chance to ‘scream in space’ using smartphone technology

fpjl2 — Thu, 25 Oct 2012 13:04:33 +0000

It was Ridley Scott’s film Alien that gave us the now legendary tagline: In space no one can hear you scream. Now, a Cambridge student society will use the technology in your pocket to find out if this is really the case.

Cambridge ̽��ֱ�� Spaceflight (CUSF) will be uploading videos of people screaming into a specially developed smartphone app, housed on a Google Android phone that will be shot into space as part of a satellite payload in early December. Once in orbit, the phone will play the screams at full volume, while at the same time recording audio.

̽��ֱ��phone will then relay back to Earth pictures of each ‘scream’ video playing against the spectacular view from the phone's inbuilt camera, along with a sound file that may or may not contain the scream captured in the vacuum of space, although the members of CUSF are not holding their collective breath.

“Obviously, we’re not expecting to get much back, there may be some buzzing, but this is more about getting young people interested in satellites and acoustics, perhaps encouraging them to consider future study in science or engineering” said Edward Cunningham, a physics undergraduate at Churchill College and one of the members of CUSF.

With this in mind, the team are asking members of the public to submit their own screams for galactic transmission - by uploading a short ‘scream’ video to YouTube, and submitting their entry.

Each video must be at most ten seconds long, and there will be ten winning screams which can be voted for by the public on the project’s website. Screams must be entered before midnight on Sunday 4th November, after which the winning videos will be announced and loaded onto the phone in readiness for a launch before the end of this year.

̽��ֱ��‘scream in space’ app is one of four phone apps that will be on board STRaND-1 - a smartphone nanosatellite - built by a team from Surrey Satellite Technology Ltd and the ̽��ֱ�� of Surrey’s Space Centre. During the summer of 2011, the STRaND (Surrey Training Research and Nanosatellite Demonstration) team ran a Facebook competition to find apps to go into orbit - and CUSF’s screaming app was one of the winners.

“We came across the competition and wanted to enter, which got us thinking about what smartphones have that a standard satellite doesn’t,” said Cunningham. “Smartphones have got a speaker and a microphone, so we wanted to do something engaging with these functions.”

̽��ֱ��STRaND-1 project will be testing the capabilities of a smartphone to control a satellite in space. ̽��ֱ��phone will run on Android's open-source operating system. A computer, built at the Surrey Space Centre, will test the vital statistics of the phone once in space. When all the tests are complete, the plan is to switch off the micro-computer and the smartphone will be used to operate parts of the satellite. At its lowest, the phone will orbit 400km above the Earth, roughly the same as the International Space Station.

"Modern smartphones are pretty amazing," said Shaun Kenyon, the project manager at Surrey Satellite Technology. “We want to see if the phone works up there, and if it does, we want to see if the phone can control a satellite."

Using smartphone technology to control space hardware is something that CUSF themselves continue to explore. ̽��ֱ��student society has already sent several Android smartphones into the stratosphere as flight computers for high altitude balloon launches, building custom apps to navigate.

“This project reflects the gradual shift of the space sector out of the exclusive domain of governments with multi-billion budgets, and into the hands of smaller ventures,” said Cunningham. “With the Android phone, you benefit from the extensive development carried out in the consumer context, and for almost no money at all. It's no coincidence that NASA has a PhoneSat project of their own.”

CUSF have previously shown that an Android phone works successfully as a standalone flight computer at a similar altitude to the one Felix Baumgartner recently performed his skydive from, but the opportunity to produce an app to run on the first smartphone in orbit is one CUSF members are thrilled about:

“ ̽��ֱ��principle of using a low-cost consumer device to do something high tech and new on a shoestring budget is something we really endorse. We often use readily available materials in our own projects,” said Cunningham.

“STRaND-1 is doing something that has never been done before and something you definitely can’t do every day. We see the project as a great opportunity to promote interest in space and also have some fun!”

For more information, contact Fred Lewsey (fred.lewsey@admin.cam.ac.uk) at the ̽��ֱ�� of Cambridge Office of External Affairs and Communications.

Cambridge students will be loading human screams onto a smartphone that will be blasted into outer space later this year. ̽��ֱ��public are invited to submit their screams, which will be emitted while in orbit at the same time as the phone records - to test if it’s possible to capture the sound of screaming in space.

It's no coincidence that NASA has a PhoneSat project of their own.

Edward Cunningham

CUSF

Image taken in stratosphere using Android phone, from previous CUSF project ‘Squirrel 3’ which used smartphone to pilot high-altitude balloon

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High Speed at the Edge of Space

ns480 — Thu, 30 Jun 2011 10:53:36 +0000

Students from the Cambridge ̽��ֱ�� Spaceflight team (CUSF) have successfully tested model parachutes for the ExoMars lander. ̽��ֱ��ExoMars lander project is a European-led robotic mission to Mars. Working in conjunction with the European Space Agency, the student team tested a model of a parachute capable of landing on Mars, by re-entering the Earth’s atmosphere at 450mph.

Entry, Descent, and Landing (EDL) is perhaps the most challenging part of any Mars lander mission. ̽��ֱ��process requires a complex system of heat shields, parachutes, retro-rockets and airbags, all having to assemble themselves mid-air.

"Six Minutes of Terror" is how engineers describe the process of EDL as a failure in any one part would lead to almost certain mission failure.

“ ̽��ֱ��Spaceflight team's testing method has not only been successful but is an extremely cost effective way to test parachutes in a Mars-like environment,” said Iain Waugh, second year PhD student at the ̽��ֱ�� of Cambridge.

̽��ֱ��testing method developed by the CUSF team costs only £1000 per launch to test one of the 1/10^th scale parachutes. Previously, only full scale parachutes had been tested in this way, with costs of over a quarter of a million dollars per test. For a new planetary lander project, the CUSF method will allow lots of initial parachute design to be tested cheaply, before choosing the best designs to go forward to the more expensive full scale tests.

Iain Waugh added: “Mars has an atmosphere more than one hundred times thinner than Earth's, and re-creating these high velocity, low density flows in a wind tunnel is a hugely expensive, if not impossible, task”.

Using their experience with high altitude scientific balloons and instrumentation, the Spaceflight team built a balloon-lofted vehicle packed with a test parachute. This was taken to the top of the atmosphere, where the air is a similar density to the surface of Mars.

̽��ֱ��vehicle was then instructed by remote control to free-fall for an amount of time calculated to let it accelerate to Mach 0.8 (Mach 0.8 means 80% of the speed of sound), the parachute was then deployed.

̽��ֱ��team monitored its inflation using a suite of instrumentation including accelerometers, gyroscopes and a high speed camera.

Slow motion video footage shows the parachutes flight during one of the low-speed system development tests. At 24km, the vehicle cuts away from the balloon, and a rope from the balloon immediately pulls the parachute out of the deployment bag. Because the vehicle is going so slowly, and the air is so thin, the parachute takes a few seconds to inflate (the video is 10x slower than real-life) and the vehicle tumbles. In the high-speed parachute test, the parachute was deployed at Mach 0.8 (an airspeed of 250m/s) and was fully inflated in 1/20th of a second.

̽��ֱ��team recently presented their work at the 21st AIAA Aerodynamic Decelerator Systems Conference in Dublin, where it took first place in the Best Student Paper competition.

Cambridge ̽��ֱ�� Spaceflight is a student-run society formed in 2006 to experiment with low-cost spaceflight.

Cambridge students have tested a parachute capable of safely landing a probe on Mars.

Mars has an atmosphere more than one hundred times thinner than Earth's, and re-creating these high velocity, low density flows in a wind tunnel is a hugely expensive, if not impossible, task”

Iain Waugh

Cambridge ̽��ֱ�� Spaceflight

Predeployed nowatermark

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