Powered vs gliding reentry - weight penalty

(MattWriter) :

Any spacecraft designed to return to Earth under control (as opposed to
ballistic reentry) has to carry a substantial amount of dead wight. For a
winged glider like the shuttle, it's the wings. For a DC-X-type powered
design, it's landing gear and extra propellants, since you need your
engines to
land. I know it's not this simple - the airframe design is different due
to
different stresses, etc. - but in general, which of these approaches
requires you to carry more extra weight on launch?

Not true. You are making assumtions before looking at all options.

There is at least one design that after doing a ballistic reentry comes to a
stop a couple of hundred feet above sea level because the base design is
light than air once all the fuel is used. How do you define dead weight in
that context?

Someone has suggested mid-air capture as a recovery mode.

Then there is my 'as crazy as a loon' idea of a wheeled lanuch sled that also
is used for the landing phase.

The fact is the range of possible designs has barely been explored.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

Earl Colby Pottinger wrote in message ...
...
different stresses, etc. - but in general, which of these approaches
requires you to carry more extra weight on launch?

Not true. You are making assumtions before looking at all options.

There is at least one design that after doing a ballistic reentry comes to a
stop a couple of hundred feet above sea level because the base design is
light than air once all the fuel is used. How do you define dead weight in
that context?

Someone has suggested mid-air capture as a recovery mode.

Then there is my 'as crazy as a loon' idea of a wheeled lanuch sled that also
is used for the landing phase.

The fact is the range of possible designs has barely been explored.

The following two fall somewhere in between gliding and powered
recovery:

Rotor recovery a la roton
Peter Lynn's Tethered free-flying wings concept
http://groups.google.com/groups?selm...le.snap.net.nz

Earl Colby Pottinger wrote in message ...
...
different stresses, etc. - but in general, which of these approaches
requires you to carry more extra weight on launch?

Not true. You are making assumtions before looking at all options.

There is at least one design that after doing a ballistic reentry comes to a
stop a couple of hundred feet above sea level because the base design is
light than air once all the fuel is used. How do you define dead weight in
that context?

Someone has suggested mid-air capture as a recovery mode.

Then there is my 'as crazy as a loon' idea of a wheeled lanuch sled that also
is used for the landing phase.

The fact is the range of possible designs has barely been explored.

The following two fall somewhere in between gliding and powered
recovery:

Rotor recovery a la roton
Peter Lynn's Tethered free-flying wings concept
http://groups.google.com/groups?selm...le.snap.net.nz

but in general, which of these approaches requires you to carry more extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of
landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the lightest.
It does require nerves of steel - if the ship fluffs the retro burn at 5000'
AGL and 300kts, in 10 seconds you go splat!

(David Shannon) wrote in message . com...
but in general, which of these approaches requires you to carry more extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of
landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the lightest.
It does require nerves of steel - if the ship fluffs the retro burn at 5000'
AGL and 300kts, in 10 seconds you go splat!

I suspect that the propellants required for even a sporty vertical
landing are more than a parachute (about 5 percent of the landing mass).
Wings designed for reentry and landing--not exit at gross mass--
can, IMO, be competitive with vertical landing propellants in a
1-g gravity field and 1 atmosphere air density.

Best regards,
Len (Cormier)
PanAero, Inc.
(replace x with len) ( http://www.tour2space.com )

(David Shannon) wrote in message . com...
but in general, which of these approaches requires you to carry more extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of
landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the lightest.
It does require nerves of steel - if the ship fluffs the retro burn at 5000'
AGL and 300kts, in 10 seconds you go splat!

I suspect that the propellants required for even a sporty vertical
landing are more than a parachute (about 5 percent of the landing mass).
Wings designed for reentry and landing--not exit at gross mass--
can, IMO, be competitive with vertical landing propellants in a
1-g gravity field and 1 atmosphere air density.

Best regards,
Len (Cormier)
PanAero, Inc.
(replace x with len) ( http://www.tour2space.com )

(David Shannon) :

but in general, which of these approaches requires you to carry more
extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of

landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the
lightest.
It does require nerves of steel - if the ship fluffs the retro burn at
5000'
AGL and 300kts, in 10 seconds you go splat!

Extra data point, Armadillo AeroSpace is now considering using powered
landing instead of a parachute because of the smaller landing footprint. The
footprint size is affecting getting insurance, the smaller the footprint the
more confident the insuring company is that you will not land accidentally on
top of someone at random.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

(David Shannon) :

but in general, which of these approaches requires you to carry more
extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of

landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the
lightest.
It does require nerves of steel - if the ship fluffs the retro burn at
5000'
AGL and 300kts, in 10 seconds you go splat!

Extra data point, Armadillo AeroSpace is now considering using powered
landing instead of a parachute because of the smaller landing footprint. The
footprint size is affecting getting insurance, the smaller the footprint the
more confident the insuring company is that you will not land accidentally on
top of someone at random.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

but in general, which of these approaches requires you to carry more extra
weight on launch?

For a given payload, a winged spacecraft weighs a minimum 15% more, and
typically 50-250% more.

(see http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld017.htm )

A capsule/DC-X vehicle has all acceleration loads in the same direction,
and the CoG in a favourable location.

But there is no free lunch.

A capsule with a parachute (the absolute lightest) gives up the option of
landing if weather is bad.
If returning to runway it needs wheels, if simple ones.
If splashing down it requires flotation gear (and a retrieval ship).

The DC-X is better off (retro fuel proabably weighs about the same as a
parachute), but the heat shielding becomes more complex. For a mature
technology and Return-on-demand missions the DC-X comes out as the lightest.
It does require nerves of steel - if the ship fluffs the retro burn at 5000'
AGL and 300kts, in 10 seconds you go splat!