Dragon returns home
After a month docked to ISS, SpaceX’s Dragon capsule has successfully splashed down in the Pacific.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
After a month docked to ISS, SpaceX’s Dragon capsule has successfully splashed down in the Pacific.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
It is interesting that from the time of retrograde burn, it takes about 50 min till in the drink. A third of the way around the earth to slow down.
Some or much of that 1/3 orbit is the spacecraft decreasing in altitude until it reaches what is called atmospheric interface, where the spacecraft starts slowing down due to the atmosphere. This probably takes place less than 1,000 miles from the landing site.
This video, from a Dragon reentry in May 2012, shows an example of how SpaceX does its final phase of reentry and how long it may take:
https://www.youtube.com/watch?v=PhSuKTYDMPk (10-minute video)
When they return Dragons on land, they won’t use parachutes, so the time to landing will be less.
Edward
Wouldn’t that require a lot more fuel sans parachutes? Just curious.
Mr. Williams,
The dramatic part of re-entry is the extreme heating as a capsule moving at just below orbital velocity hits the first bits of atmosphere thick enough to be worthy of the name. The flames and drama don’t last long, though. Then the capsule continues to fall at a terminal velocity which diminishes steadily as the atmosphere thickens with decreasing altitude. Capsules are blunt and have a lot of surface area relative to their mass so their terminal velocity in the lower atmosphere is usually in the 200 – 300 miles per hour range. The atmosphere does most of the braking before the main parachutes ever come out or, as will be the case with Dragon 2 after some initial parachute landings, the landing rockets light.
The fuel that will be used by Dragon 2 to land isn’t parasitic mass in any event. That fuel has to be carried as a safety precaution in case the dual-purpose launch escape/landing motors have to be fired on ascent due to some major booster malfunction. In such a case, the landing would have to be by parachute as the fuel would already have been expended getting the capsule away from a distressed booster. So Dragon 2’s will have a “belt and suspenders” landing system. On descent, the landing motors will be test-fired while still a long way up and the parachutes will only be used if there is a serious enough malfunction detected to prevent a powered descent. So, once a few initial parachute-only landings are accomplished, whether going up or coming down, Dragon 2 will only deploy chutes in an emergency, but they will always be carried.
Dick has it right.
Dragon 2 will not have an escape tower, as the Mercuries, Geminis, Apollos did and the Orion has. Building the escape system into the capsule allows this same system to be used to slow down to a gentle landing when it is not used in an emergency escape, in which the parachutes would gently splash the capsule into the ocean.
Without the weight of an escape tower, the first stage need not accelerate that mass, which should be a big fuel-saver. However, the escape/landing system and its fuel will have to be accelerated by the upper stage, which should be a big fuel penalty.
On the third hand (the gripping hand, for Niven/Pournelle fans), using the parachutes to set down on land is not desirable, because the wind can take the capsule far from the landing pad, and using the thrusters to land on the pad prevents sea-water contamination or corrosion and allows for faster turn-around time with a resuable capsule.
As we already know, SpaceX is willing to expend a little extra fuel and take the penalty in maximum payload in order to reduce the overall cost of operation by reusing flight hardware.
Great Motie reference Edward! Always been a big Niven/Pournelle fan and I believe I have read all of the Known Space works after getting hooked (like so many others) on “Ringworld” :-)
Although IIRC the Mote books are set in a different timeline…