SpaceX delays launch of Polaris Dawn private spacewalk mission to Aug. 27

[Admin]

SpaceX's private Polaris Dawn mission will wait one more day for launch as the company completes preflight checkouts of the spacecraft.

SpaceX delays launch of Polaris Dawn private spacewalk mission to Aug. 27 : Read more

 

[PawAngel]

Godspeed. A question for everyone: Could a Dragon Capsul, powered by a Falcon 9, make a loop trip around the moon and back? Or would we need a Falcon Heavy? Bonus: If Jared Isaacman wanted to finance this, would NASA let him do it?

 

[24launch]

This was actually discussed at length a while back in another space forum. The concensus (mostly) was that a Falcon Heavy could do it - factoring in the additional weight of the additional food, water, O2, CO2 scrubbers and other consumables required for a multi-day mission.

But there are lots of other considerations not the least of which is the heat shield. Re-entering from Earth orbit, Dragon is doing around 17.5K miles per hour. But a return trajectory from the Moon it would be going around 25K miles per hour. That's a LOT more speed to have to scrub off during re-entry thus a LOT more heating and ablation. Elon had said a while back the heat shields on Dragon were tested at significantly higher heating and stresses than normal Earth orbit re-entry (so they had established a large safety margin) and that it should probably be fine for a lunar re-entry. But probably and definitely are certainly not synonmous when lives are on the line!

Other issues would be communications. Communicating with a ground station in 220 mile orbit vs 228,000 miles is a massive amount of signal to noise loss. One of the cool experiments with Polaris Dawn is using laser communications, so that would allow a much tighter beam from Lunar Orbit, and with Starlink blanking Earth orbit, you wouldn't have to be trying to hit a ground station that's not directly in your line-of-sight.

If you remember a while back there was the Dear Moon mission to be financed by the Japanese billionaire with an orbit around the Moon in a yet to be designed Dragon capsule. Unfortunately in the time since it was proposed he lost 1/2 his fortune and canceled the deal.

While such a mission around the moon would most likely be done with NASA's cooperation and no doubt tapping into their expertise, really the sole approving government body would be the FAA in granting not only the launch license but the very importaint return/reenter license!

 

[PawAngel]

Thanks for the quick reply. So what we need is for Elon to send an empty Dragon to see how well the heat shield holds up. One thing about this is that Dragon might could be used as a rescue ship for Artemis. He can pop up a Falcon within days if not hours if one were ready to go. Apollo 13 got very lucky.

 

[jordiheguilor]

On another article I read about the electronics and the radiation in the Van Allen inner belt:

"To make sure the spacecraft’s avionics — or electronics used for navigation and communication — could survive the heavy radiation environment encountered during the Polaris Dawn mission, engineers “literally strapped a lot of the avionics to a gurney and brought it to an oncology lab,” Isaacman said."

I wouldn't want to be subject to the amount of radiation that can fry electronics. It doesn't seem a healthy thing to do in the long term.

 

[Unclear Engineer]

From https://en.wikipedia.org/wiki/Van_Allen_radiation_belt :
"The total radiation received by the astronauts varied from mission-to-mission but was measured to be between 0.16 and 1.14 rads (1.6 and 11.4 mGy), much less than the standard of 5 rem (50 mSv)[c] per year set by the United States Atomic Energy Commission for people who work with radioactivity."

Of course, that was with the shielding provided by the Apollo capsule. Probably not as much shielding in the Dragon capsule structure.

 

[jordiheguilor]

From https://en.wikipedia.org/wiki/Van_Allen_radiation_belt :
"The total radiation received by the astronauts varied from mission-to-mission but was measured to be between 0.16 and 1.14 rads (1.6 and 11.4 mGy), much less than the standard of 5 rem (50 mSv)[c] per year set by the United States Atomic Energy Commission for people who work with radioactivity."

Of course, that was with the shielding provided by the Apollo capsule. Probably not as much shielding in the Dragon capsule structure.

But aren't these astronauts going to spend two or three days in the Van Allen belts, while the Apollo astronauts just crossed them?

 

[Unclear Engineer]

My comment was directed at post #3 about sending a Dragon capsule to loop around the Moon.

From the link I provided:

"The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii (L values of 1.2 to 3) or 1,000 km (620 mi) to 12,000 km (7,500 mi) above the Earth.[3][15] In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly, the inner boundary may decline to roughly 200 km"

For the Polaris Dawn mission orbit, see https://en.wikipedia.org/wiki/Polaris_Dawn . It says:
"The Dragon capsule will initially be inserted into a highly elliptical orbit with an apogee that will take them up to 1,200 kilometers (750 mi) away from Earth and a perigee that will take the crew through the South Atlantic Anomaly at an altitude of 190 kilometers (120 mi). The crew expects that making just two or three passes of the anomaly at that altitude will expose them to the equivalent radiation load of three months on the International Space Station so that they may conduct experiments to study the health effects of space radiation and spaceflight on the human body. During this time, the crew will also do extensive checks of the Dragon capsule. If no faults are found, they will fire thrusters to will take them up to 1,400 kilometers (870 mi) away from Earth."

For ISS astronauts, measurements from the crew's personal dosimeters indicate a range from 12 to 28.8 milli rads per day. So, 1.1 to 2.6 rads in 3 months.

Note that the "South Atlantic Anomaly" is a magnetic "north pole" located about 25 degrees south of the equator. See https://en.wikipedia.org/wiki/South_Atlantic_Anomaly .