Blue Origin's New Shepard
suborbital booster and SpaceX's Falcon 9 suborbital booster may look alike at
first glance. However, the Falcon 9 carries a staggering 130
tons at launch while New Shepard carries only 5. The two vehicles are, in fact,
completely different designs for two completely different purposes. Blue
Origin's booster is designed to carry a single crew capsule to space (100
kilometers up), while SpaceX's Falcon 9 booster (and the Falcon 9 upper stage)
bring payloads to orbit. This requires about four times as much total energy as
New Shepard's 100.5km hop into space.
New Shepard's trajectory brings it
up and back down with only two burns: a launch burn and a landing burn. The
Falcon 9, on the other hand, has to deliver (with the upper stage) a payload to
orbit. This means that the Falcon 9 has to angle itself towards the horizon
during launch; at stage separation (when the upper stage detaches to complete
the mission), the Falcon 9 booster is travelling faster horizontally than
vertically. This velocity is reversed with three more engine restarts (four
including the launch).
The boostback burn brings the
vehicle's trajectory back towards land. However, the booster will reenter the
atmosphere at a speed far too fast to survive. So at an altitude of about 70km,
three of the engines are restarted to
slow the vehicle down before it hits the thicker, lower parts of the
atmosphere. When the entry burn ends, the Falcon 9 booster is only 40km above
the ocean, on a trajectory that will drop it harmlessly into the ocean in case
of a failed landing burn.
The third, critical, burn the
Falcon 9 performs is the landing burn. This is a single-engine burn, starting
about 30 seconds before touchdown. The single center engine reignites a final
time as the vehicle plummets towards the ground; the grid fins reorient the
vehicle and push it towards the landing pad, and about 5 seconds from touchdown, the landing legs
unfold and the booster touches down on the landing pad.
Another major advantage New Shepard
has over the Falcon 9 is its deep-throttleable BE-3 engine. Most rocket engines
have a very limited throttle range (and some can't throttle at all). The Merlin
1D, nine of which are used on the Falcon 9 booster, can throttle from about 65%
to 100%, and that is very, very deep throttling for an engine of its size. New
Shepard's BE-3, on the other hand, can throttle down to at least 40%. This
means that New Shepard can hover while landing, which gives them more time to
line up and touch down softly. The Falcon 9 cannot hover at all and must reach
zero velocity the moment it touches the pad or it will begin to rise up again.
This necessitates more accurate and advanced control systems.
In closing, it's unfair to compare
the two vehicles. New Shepard is designed for several minutes of microgravity,
while Falcon 9 is designed to carry satellites into orbit. The vehicles perform
their respective tasks admirably.
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