The Dream of Solar Sailing ~ Credit: Planetary Society
The Planetary Society's LightSail 2 spacecraft is ready to embark on a challenging mission to demonstrate the power of sunlight for propulsion.
Weighing just 5 kilograms, the loaf-of-bread-sized spacecraft, known as a CubeSat, is scheduled to lift off on 22 June 2019 aboard a SpaceX Falcon Heavy rocket from Kennedy Space Center, Florida. Once in space, LightSail 2 will deploy a boxing ring-sized solar sail and attempt to raise its orbit using the gentle push from solar photons. ...
If successful, LightSail 2 will become the first spacecraft to raise its orbit around the Earth using sunlight. While light has no mass, it has momentum that can be transferred to other objects. A solar sail harnesses this momentum for propulsion. LightSail 2 will demonstrate the application of solar sailing for CubeSats, small, standardized spacecraft that have made spaceflight more affordable for academics, government organizations, and private institutions.
LightSail 2 will ride to space aboard the Department of Defense's Space Test Program-2 (STP-2) mission scheduled for launch on 22 June 2019, which will send 24 spacecraft to 3 different orbits. LightSail 2 itself will be enclosed within Prox-1, a Georgia Tech-designed spacecraft originally built to demonstrate close-encounter operations with other spacecraft. Prox-1 will deploy LightSail 2 seven days after launch. ...
LightSail 2 is officially in space! The Planetary Society's solar sail CubeSat lifted off from Kennedy Space Center, Florida on 25 June at 02:30 EDT (06:30 UTC). The late-night launch came courtesy of SpaceX's triple-booster Falcon Heavy rocket, which was carrying 24 spacecraft for the U.S. Air Force's STP-2 mission.
Launch was originally scheduled to occur at 23:30 EDT on 24 June (03:30 UTC on 25 June). SpaceX delayed the liftoff time by 3 hours to complete additional ground system checkouts.
During its ride to orbit, LightSail 2 was tucked safely inside its Prox-1 carrier spacecraft. The Falcon Heavy upper stage's payload stack released Prox-1 about an hour and 20 minutes after liftoff, at an altitude of roughly 720 kilometers. Prox-1 will house LightSail 2 for 1 week, allowing time for other vehicles released into the same orbit to drift apart so each can be identified individually. LightSail 2 deployment is set for 2 July. ...
First Contact! LightSail 2 Phones Home to Mission Control
LightSail 2 Mission Highlights ~ Planetary Society
The Planetary Society's LightSail 2 spacecraft sprang loose from its Prox-1 carrier vehicle as planned today, and sent its first signals back to mission control at Cal Poly San Luis Obispo in California.
The CubeSat, about the size of a loaf of bread, was scheduled to leave Prox-1 precisely 7 days after both spacecraft successfully flew to orbit aboard a SpaceX Falcon Heavy rocket. Following deployment from its spring-loaded enclosure known as a P-POD, LightSail 2 deployed its radio antenna and began transmitting health and status data, as well as a morse code beacon indicating its call sign. The mission team received LightSail 2's first signals on 2 July at 01:34 PDT (08:34 UTC), as the spacecraft passed over Cal Poly. ...
More data collected during additional ground station passes today will be used to evaluate the health and status of the spacecraft. The next available opportunity for contact is 3 July at roughly 00:30 UTC (2 July at 20:30 EDT), when LightSail 2 flies over Georgia Tech.
The team will spend about a week checking out LightSail 2's systems, exercising the spacecraft’s momentum wheel, and taking camera test images before and after deployment of the CubeSat’s dual-sided solar panels. Following the successful completion of these tests, the team will deploy the 32-square-meter solar sail, about the size of a boxing ring. A time for the solar sail deployment attempt will be announced later. ...
Re: First Contact! LightSail 2 Phones Home to Mission Control
The CubeSat, about the size of a loaf of bread, was scheduled to leave Prox-1 precisely 7 days after both spacecraft successfully flew to orbit aboard a SpaceX Falcon Heavy rocket. Following deployment from its spring-loaded enclosure known as a P-POD, LightSail 2 deployed its radio antenna and began transmitting health and status data, as well as a morse code beacon indicating its call sign. The mission team received LightSail 2's first signals on 2 July at 01:34 PDT (08:34 UTC), as the spacecraft passed over Cal Poly. ...
The Planetary Society's LightSail 2 spacecraft is almost ready to go solar sailing.
Mission officials today cleared the spacecraft for a possible sail deployment attempt on Tuesday, 23 July 2019, during a ground station pass that starts at roughly 11:22 PDT (18:22 UTC). A backup pass is available the following orbit starting at 13:07 PDT (20:07 UTC). These times may change slightly as new orbit predictions become available.
Live sail deployment coverage will be available at planetary.org/live. A video and audio stream from mission control, located at Cal Poly San Luis Obispo in California, will be available during ground station passes. Rolling updates will also be posted on the page for context. ...
Re: PS: LightSail 2 Set to Launch Next Month
Posted: Mon Jul 22, 2019 1:08 pm
by BDanielMayfield
I don't doubt the truthfulness of this statement,
While light has no mass, it has momentum that can be transferred to other objects.
but I'm sketchy on how to explain this. After all, isn't momentum normally the product of mass times speed? If mass is zero ... ?
Bruce
Re: PS: LightSail 2 Set to Launch Next Month
Posted: Mon Jul 22, 2019 2:44 pm
by neufer
BDanielMayfield wrote: ↑Mon Jul 22, 2019 1:08 pm
I don't doubt the truthfulness of this statement,
While light has no mass, it has momentum that can be transferred to other objects.
but I'm sketchy on how to explain this. After all, isn't momentum normally the product of mass times speed? If mass is zero ... ?
A photon has a REST mass of zero...but it can never be brought to rest.
A photon of energy E= hν
has a momentum p = E/c and an 'equivalent mass' of E/c2.
Re: PS: LightSail 2 Set to Launch Next Month
Posted: Mon Jul 22, 2019 3:01 pm
by TheOtherBruce
One thing I can't quite visualise, particularly from the Mission Highlight video upthread; how is the sail steered? I didn't realise something as small as a cubesat could have anything inside capable of controlling its attitude.
Torque-a-matter
Posted: Mon Jul 22, 2019 4:29 pm
by neufer
TheOtherBruce wrote: ↑Mon Jul 22, 2019 3:01 pm
One thing I can't quite visualise, particularly from the Mission Highlight video upthread; how is the sail steered? I didn't realise something as small as a cubesat could have anything inside capable of controlling its attitude.
<<Four sun sensors are installed at the end of the deployable solar panels to deliver data for the calculation of the solar vector for attitude control. Each of the two-axis sun sensors has a 150° field of view and a resolution of 2.7° creating an accuracy of +/-5° in the determination of the sun direction. Three single-axis gyros are used to keep track of the three-axis attitude of the spacecraft, each gyro working at a 0.012°/sec resolution.
Attitude actuation is accomplished through 90 by 22-millimter, 150-gram magnetic torque rods that are used to create angular momentum by running a current through coils in the presence of Earth’s magnetic field. The torquers are regulated by computers that control the current that is passing through the coils in order to control the force generated on each axis by processing data provided by a magnetometer. A momentum wheel is used to augment attitude control to adjust the slew rate of the satellite to ensure proper sun-pointing. The wheel assembly weighs 220 grams and is 75 by 65 by 38 millimeters in size with a nominal momentum of 0.05Nms supporting body rates up to 2.5°/sec.>>
Re: PS: LightSail 2 Set to Launch Next Month
Posted: Mon Jul 22, 2019 6:25 pm
by TheOtherBruce
Thanks for the info — didn't know they could build these things so tiny.
