NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: sanman on 12/16/2020 08:02 pm
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I wanted to ask about Starship's skydiver/bellyflop descent. Has the idea for this type of descent ever been previously proposed before in some prior vehicle concept, or is SpaceX the original innovator of this idea?
Can skydiver/bellyflop descent be described as a variant of blunt-body dynamics, with the added feature of active balancing through large control surfaces? (It almost seems like a more rigid version of a steerable parachute.)
We've all heard the sonic booms from Falcon-9's descent and landings -- what are Starship's sonics boom likely to sound like by comparison? Since Starship in skydiver/bellyflop will reach terminal velocity much higher up, as opposed to F9's more rapid descent terminating in hoverslam, then should the sonic booms be heard much before Starship's arrival at the landing site?
I've read that Starship's terminal velocity from skydiver/bellyflop descent will be ~200kph, which seems surprisingly low. At what altitude is it expected to reach terminal velocity, during standard descent from orbit?
While skydiver/bellyflop descent is supposed to allow flexibility in EDL for both Earth and Martian atmospheres, and does not require a pre-built runway to land on, are there any other advantages to it?
For mission roles that only involve landing on Earth specifically, why would skydiver/bellyflop be preferable to glide re-entry?
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(...)
We've all heard the sonic booms from Falcon-9's descent and landings -- what are Starship's sonics boom likely to sound like by comparison? Since Starship in skydiver/bellyflop will reach terminal velocity much higher up, as opposed to F9's more rapid descent terminating in hoverslam, then should the sonic booms be heard much before Starship's arrival at the landing site?
(...)
F9 approaches coastal landing sites from the ocean. Starship coming in for landing approaches the Cape from the west and crosses densely populated regions of the Florida peninsula. See the discussion starting at https://forum.nasaspaceflight.com/index.php?topic=48720.160 (https://forum.nasaspaceflight.com/index.php?topic=48720.160)
Some estimates indicate that Starship will result in 2 to 3 times higher overpressure event than the Space Shuttle.
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I wanted to ask about Starship's skydiver/bellyflop descent. Has the idea for this type of descent ever been previously proposed before in some prior vehicle concept, or is SpaceX the original innovator of this idea?
*snip*
Starship is not the first. The Delta Clipper would have reentered and landed essentially the same way.
The DC-XA test vehicle demonstrated the maneuver in a test flight.
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"White Sands, NM, July 7, 1995
The Delta Clipper Experimental Demonstrates Re-Entry Maneuver.
The Delta Clipper-Experimental launch vehicle (DC-X) has successfully completed its eighth flight while performing the critical rotation maneuver that a vertical-landing rocket would execute after re-entering the Earth's atmosphere.
After climbing to 8,200 feet at a maximum ascent rate of 240 feet per second today, the McDonnell Douglas-built experimental rocket set up for the maneuver by pointing its nose 10 degrees below the horizon, and then it rotated 138 degrees to a base-first flight attitude. The DC-X then landed base first using its four Pratt & Whitney RL-10 engines as brakes. 'Today, the DC-X demonstrated the maneuver required by a full-scale vertical landing reusable launch vehicle using propulsion control,' said Save Schweikle, director of McDonnell Douglas' DC-X program. 'The incremental expansion of the DC-X flight envelope over the previous flights has been in preparation for this critical maneuver,' he explained. The test flight for the DC-X, a vertical-takeoff, vertical-landing rocket, began at 7:02 a.m. MDT at the U.S. Army's White Sands Missile Range. Total flight time was two minutes and four seconds.
The maximum altitude of today's flight was 8,200 feet, which exceeded the 5,700 feet flown during the last flight on June 12. During the assent, the DC-X traveled 2,100 feet down range from the flight pad and performed the 138 degree rotation maneuver as it returned toward the landing site. The DC-X descended base first at 165 feet per second from an altitude of about 7,000 feet, using its engines to brake for a landing."
https://www.hq.nasa.gov/pao/History/x-33/dcxtests.html
Video of the 8th flight:
https://youtu.be/wv9n9Casp1o
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I wanted to ask about Starship's skydiver/bellyflop descent. Has the idea for this type of descent ever been previously proposed before in some prior vehicle concept, or is SpaceX the original innovator of this idea?
*snip*
Starship is not the first. The Delta Clipper would have reentered and landed essentially the same way.
The DC-XA test vehicle demonstrated the maneuver in a test flight.
Not quite as the 4 RL-10 engines was always firing through-out the flight. There was never any in-flight shut-down and re-ignition the way Starship does it. DC-X always had the engines going so there was never any ignition concerns and quick throttle-modulation required.