Elon Musk's SpaceX to build 'Grasshopper' hover-rocket

On Oct 2, 10:33*pm, Alan Erskine wrote:
On 3/10/2011 3:03 PM, Mike DiCenso wrote:





On Oct 2, 1:48 am, Alan *wrote:
On 2/10/2011 7:29 PM, Mike DiCenso wrote:

On Oct 1, 10:16 pm, Alan * *wrote:
On 30/09/2011 7:09 AM, wrote:
You mean the Boeing idea for the shuttle (if I remember correctly, it
involved four boosters, two on each side of the ET)?

Actually, that system was two big LOX/Kerosene boosters that were
supposed to be powered by surplus F-1As
that had been intended for use on the Saturn V, but were never used
despite being built and certified.
-Mike

To answer your question, the foam was dislodged by vibration from the
SRB, not just aerodynamic forces.

Yes, but as Brian points out, it is not likely that F-1As would have
been gentle enough to prevent the foam from breaking off. Just look at
the ice that was dislodged by the Saturn V during launch, or on the
Energia booster, which also dislodged ice, which in turn damaged the
tiles on the Buran orbiter.
-Mike

Probably wouldn't have used foam anyway as the F-1s were LOX/RP1. *Foam
is used on the LH2 tank to reduce boil-off. *It's also used on the O2
tank but not as thick and this isn't the area where foam separated.- Hide quoted text -

I think you're a bit confused. Unless the F-1s were mounted on the
base of the ET, the SSMEs still need to be powered by LOX/LH2, so the
F1s are on the side-mounted FLRBs while the ET is still largely the
same. My examples above show that even an all-liquid system is not
gentle enough, and you still have ice dislodging and falling down
along with other debris. So a ride on two FLRBs, each powered by two
F-1As might not have been enough to prevent a Columbia-style accident.
Only the removal of the foam bipod ramp (replaced with the titanium/
heater system one) and reducing other sources of foam would have
helped.
-Mike

On Mon, 03 Oct 2011 16:33:14 +1100, Alan Erskine
wrote:


Probably wouldn't have used foam anyway as the F-1s were LOX/RP1. Foam
is used on the LH2 tank to reduce boil-off. It's also used on the O2
tank but not as thick and this isn't the area where foam separated.

Liquid Flyback Booster only replaces the Solid Rocket Boosters, not
the External Tank from which foam was liberated, leading to the
Columbia accident. The LO2 tank has as much foam as most of the LH2
tank, it has to withstand aerodynamic heating during ascent. The most
foam, I think is on the LH2 tank Aft Dome, which has to protect
against SRB plume recirculation heating. The Columbia was brought down
by foam on the Bipod Ramp of the intertank area.

Brian

On 4/10/2011 5:44 AM, Mike DiCenso wrote:


I think you're a bit confused. Unless the F-1s were mounted on the
base of the ET, the SSMEs still need to be powered by LOX/LH2, so the
F1s are on the side-mounted FLRBs while the ET is still largely the
same. My examples above show that even an all-liquid system is not
gentle enough, and you still have ice dislodging and falling down
along with other debris. So a ride on two FLRBs, each powered by two
F-1As might not have been enough to prevent a Columbia-style accident.
Only the removal of the foam bipod ramp (replaced with the titanium/
heater system one) and reducing other sources of foam would have
helped.
-Mike


With the spacecraft on top, it's not going to be a problem if foam
dislodges. I just don't see the justification for building this thing.

In article ,
says...

Jeff Findley wrote:

In article 92141f95-892b-4cec-a3eb-2b0043291358
, says...

Assuming they can get this to work, of course. It's an interesting
concept, to be sure. Good luck to Lord Musk-he's gonna need it. (and
no, he's not the Messiah when it comes to HSF-which a lot of folks,
especially those on spacepolitics.com, seem to think)

Certainly this is a fairly big "if". No one has attempted this before.

I'm glad Musk has the balls to try this. No other US aerospace company
seems to have the balls to do anything new on the scale that SpaceX
does.


Was it Musk who said that the best way to make a small fortune in the
space business was to start with a large fortune?

I can't remember. But there is a lot of truth to this. There was a
NASA study recently which applied different cost models to what SpaceX
has done with Falcon. It should come as no surprise that the
traditional cost plus cost models predicted costs *far* higher than
SpaceX's actual costs.

It's unlikely SpaceX will make total profits which higher than if it
were all done as a cost plus government contract. The only way to make
higher total profits would seem to be to open up new markets, which
isn't likely to happen "soon". From an investment point of view,
lowering launch costs just doesn't make much sense.

This supports the notion that Musk truly isn't in this business to make
lots of money. He appears to be in it because he eventually wants to
"go to Mars".

As Ares/Orion/SLS and etc. are proving, there is just no way we're going
to put people on Mars using NASA's "business as usual" approach. The US
"can't afford it". And by "can't afford it", I mean there is zero
political will to fund NASA at levels which would make a manned Mars
mission "affordable".

I'm waiting for SLS to collapse under its own weight as yet another
unaffordable NASA boondoggle.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker

On Mon, 03 Oct 2011 20:38:36 -0700, Fred J. McCall
wrote:


Was it Musk who said that the best way to make a small fortune in the
space business was to start with a large fortune?

Beal, I think.

Brian

On Tue, 04 Oct 2011 12:26:02 +1100, Alan Erskine
wrote:


I think you're a bit confused. Unless the F-1s were mounted on the
base of the ET, the SSMEs still need to be powered by LOX/LH2, so the
F1s are on the side-mounted FLRBs while the ET is still largely the
same. My examples above show that even an all-liquid system is not
gentle enough, and you still have ice dislodging and falling down
along with other debris. So a ride on two FLRBs, each powered by two
F-1As might not have been enough to prevent a Columbia-style accident.
Only the removal of the foam bipod ramp (replaced with the titanium/
heater system one) and reducing other sources of foam would have
helped.
-Mike


With the spacecraft on top, it's not going to be a problem if foam
dislodges. I just don't see the justification for building this thing.

You do understand that the Flyback Booster proposal was a Shuttle
upgrade initiated around 1998, right?

Brian

On Mon, 3 Oct 2011 19:26:46 +0100, Dr J R Stockton
wrote:


But they will probably run into problems making Falcon Heavy fully
reusable. If they're crossfeeding propellant from the strap-ons to the
core, the core will be too high/too fast/too far to turn around and
fly back to the Cape, but not high enough/fast enough/far enough to
reach a landing site in Europe or Africa. An ECAL-like landing in New
England or Newfoundland might be possible, but only for
high-inclination launches. The no man's land point will begin
somewhere around 4 minutes into flight, where Shuttle used to get the
"negative return" call.


There are islands in the Atlantic, although not many. Shuttle needed a
big wide runway; Falcon recovery would only need a pad.

You will be limited to which orbits you can launch to. Although I
wonder if the ground track is close enough to Puerto Rico for a
traditional GEO-bound launch.

On a day when
the Atlantic is reasonably flat, Falcon could land on an aircraft
carrier. Anything that can land on a pad of the size in the video
(IIRC) should be able to land on a Nimitz.

Rocket engine exhaust on the deck will be a huge problem, in fact I'm
pretty sure a Merlin would blast a hole in an aircraft carrier's deck.
You'd need a specialized ship like the SeaLaunch platform. Not a bad
idea, but I think this goes against the SpaceX philosophy of keeping
things as simple and low-cost as possible.

Alternatively, though perhaps not when going to ISS, launch from the
Texas coast, recover in Louisiana Mississippi, or Florida; or Cuba,
Haiti, ..., Kourou, depending in inclination and range.

Overflight of populated areas will be a huge no-no. We're not the
Russians or Chinese, who don't give a hoot if some village downrange
gets wiped out by a crashing rocket.

Brian

On Sep 29, 5:09*pm, wrote:
Whatever happened to the "Glide Back" booster proposals that
would allow the booster to fly downrange, as well as vertically,
and still be able to return to the launch site?

Elon doesn't like wings because of the extra weight. He mentions this
again during the National Press Club speech:

NATIONAL PRESS CLUB LUNCHEON WITH ELON MUSK.
http://www.spacex.com/npc-luncheon-elon-musk.php

BTW, I think the payload lost in making the vehicle reusable is being
overstated. Elon himself during the speech spoke ruefully of cutting
into the 2%-3% payload fraction of launch vehicles. But actually a
small percentage of the vehicle's dry weight, which is the important
parameter not the gross weight, would need to go the reentry/landing
systems.

The reason is this is for a multi-stage launcher, and a key fact is
for the larger first stage any extra kilo added to the first stage dry
weight subtracts only ca. 1/10th of a kilo from the payload.
And also for multi-stage launchers, the upper stage dry weight is
usually rather small, in fact frequently smaller than the payload.
We can estimate the added weight for the Falcon 9. This page
estimates the weights for this launcher:

Space Launch Report: SpaceX Falcon Data Sheet.
http://www.spacelaunchreport.com/fal...tml#components

The dry weight for the first stage is given as 19 mT, and 3 mT for
the upper stage. These weights might even be overestimated. Some
references for instance give the dry weight for the first stage as in
the range of 15 mT.
Now estimate the mass of reentry/landing systems. First, Robert
Zubrin gives an estimate of about 15% of the landed weight for reentry
thermal protection:

Reusable launch system.
http://en.wikipedia.org/wiki/Reusabl...y_heat_shields

Secondly, an estimate of 10% is often cited for the wings for glided
landing or for the fuel for powered landing:

Reusable launch system.
http://en.wikipedia.org/wiki/Reusabl...zontal_takeoff

Finally the estimated weight for the landing gear is about 3%:

Landing gear weight.
http://yarchive.net/space/launchers/...ar_weight.html

This totals to 28%. However, it is important to keep in mind that
with modern materials this can probably be reduced to half this.
So 14% of 19 mT on the first stage is 2,660 kg. But remember for a
first stage this will only subtract about 1/10th this from the
payload. So 270 kg lost.
For the second stage 14% of 3 mT is 420 kg. So the total is in the
range of 700 kg lost from the Falcon 9 payload capacity to LEO of
10,000 kg.
But by doing this you are making the vehicle reusable and cutting
costs by a factor of 100.


Bob Clark

On 5/10/2011 1:08 AM, Brian Thorn wrote:


You do understand that the Flyback Booster proposal was a Shuttle
upgrade initiated around 1998, right?

Brian

yep.

Brian Thorn wrote:

You do understand that the Flyback Booster proposal was a Shuttle
upgrade initiated around 1998, right?

When I started college in 1976 my initial plan was to go into mechanical
engineering with a focus on turbine machines because I wante dto work on
the booster stage of the propsed Space Shuttle. So that was only one of
many such proposals.