(Henry Spencer) writes:

In article .com,
wrote:
Are probes like the soviet Luna 9 & 13 considered soft landers or hard
landers? Years ago, all the sources that I came across insisted that
soft landers had to use braking rockets to cut velocity, and that the
Lunas (and, by extention, probes that use airbags, like MER) were
survivable hard landers, ejected by a bus which then crashed onto the
surface. Is this distinction still used?

That terminology isn't much heard now, perhaps because we now also have
*really* hard landers: penetrators, which come in at 200-300m/s (vs. the
10-20m/s acceptable for airbag or crushable-padding systems, and the
0-5m/s typical of rocket landing). It was played up in the 60s to
emphasize the technical superiority of Surveyor 1 over Luna 9.

Note that *all* these systems need braking rockets for a lunar landing,
because an undecelerated lunar impact is 2000-3000m/s (even from lunar
orbit, it's 1700m/s or so)

The early, unsuccessful Ranger lunar probes (numbers 3 to 5) intended to
carry out what they called a rough landing of an instrument package on
the moon. Braked by a solid rocket, the package was to be cushioned in
a balsa enclosure and surrounded by fluids. It would hit the moon at 61
m/sec, taking 3000 g's.