New Mars Forums

For a different reason,  I had to rough out essentially the same plane circa 1985.  Mine was turbojet/ramjet parallel-burn propulsion,  a similar layout,  and designed for M5 at 100-150 kft.  I did it from all open sources. 
It was so close "to reality" the FBI confiscated all my design notes,  but not my sources or my slide rule,  because I did not possess the clearances "to know about such a craft".  I have often wondered if such a thing ever got built. 
It appears in hindsight apparently not.  Although it could have been.  The delta-wing pulse detonation experimental craft (seen above Groom Lake) of about 1995 apparently led nowhere. 

GW

Yeah but neither of wikipedia's links actually has anyone saying what the T/W of the engine actually is

Has anyone consulted the T/W figures for turbojet engines?  A quick look at Wikipedia suggests that they're extraordinarily poor: The J-58 Turbojet used on the SR-71 has a thrust-to-weight of about 5.  This suggests that accelerations will be pretty low (With a L/D of 10, an extremely generous estimate at high mach (for example the Concorde was 7 and the Space Shuttle gets 1, flying hypersonically)) an engine mass of 10% of wet mass results in an acceleration of 0.4 gs at maximum thrust.  For a large craft, that corresponds to a lot of engines. 
I've always been a fan of flyback boosters, myself.  It just seems much simpler-- Make them big and dumb, and stage around 3 km/s so it's not too hard to get back.

In a previous post in this discussion thread I described an alternative mission architecture. I would like to compare with Mars Direct, and show how NASA could do it.

When I said Mars Direct could be done with 3 SLS launches for the first mission, and 2 for each mission thereafter, that means SLS with the full size upper stage and advanced solid rocket boosters. If the advanced solid rocket boosters are not available, then Mars Direct would require an additional launch.

My architecture would require:

First mission:
- 1 SLS for MAV (full-size upper stage, existing SRBs)
- 1 SLS for lab & pressurized rover (full-size upper stage, existing SRBs)
- 1 Falcon 9 for ITV
- 1 SLS for TMI stage (interim upper stage, existing SRBs)
- 1 Falcon 9 for lander & unpressurized rover
- 1 Falcon 9 for Dragon
- 1 Atlas V 402 for Dream Chaser

....

From what I've seen and heard,  the Merlin 1-D has about the same thrust as the Merlin 1-C's,  just a lower hardware weight,  for a substantially higher engine T/W ratio.  They sure sound about the same when tested on the stand in McGregor. 
Haven't seen anything yet on the Spacex site about the redesign changes for v 1.1,  but I haven't been there for a while. 
I do know Falcon-Heavy is supposed to be based on the Merlin 1-D's.  Haven't heard one of those tested yet. 
GW

...The JPL manager calmly claimed all technologies in his plan are demonstrated, including rendezvous with manned vehicle. He also referred to sample return as a $4 billion mission.
In another talk, Robert Zubrin said for the same weight as Curiosity, you could land a fully fuelled return vehicle and a tiny rover to collect samples from the immediate vicinity.
I would like to propose an alternative. Since the 2020 rover is a copy of Curiosity, which is great but by 2020 it will be "been there, done that". So my proposal is to replace that mission with a less expensive one. Rather than land a fully fuelled return vehicle, instead use ISPP. Fully demonstrate Robert Zubrin's ISPP, which means bringing hydrogen from Earth. If this requires another technology demonstrator in a laboratory on Earth, then do so. The Mars lander would include a rover about the size of Sojourner. While Spirit and Opportunity were the size of a golf cart, and Curiosity the size of an SUV, Sojourner was the size of a radio controlled toy car. Return the sample directly to Earth, similar to JPL mission "Stardust"...

Mars rover confirms dangers of space radiation.
Future manned missions to Mars will need internal shielding and advanced propulsion systems to shorten transit times, minimizing exposure to space radiation, scientists say.
by William Harwood  May 30, 2013 3:06 PM PDT

Chris Moore, deputy director of advanced exploration systems at NASA headquarters, said shorter transit times and improved shielding will be needed to protect future deep space crews.
"To get really fast trip times to cut down on radiation exposure we'd probably need nuclear thermal propulsion, and we're working with the U.S. Department of Energy to look at various types of fuel elements for these rockets," Moore said.
"But it's a long-range technology development activity and it will probably be many years before that is ready. But it is part of our design reference mission architecture for sending humans to Mars.... That could probably cut the (one-way) trip time down to around 180 days."

http://news.cnet.com/8301-11386_3-57586 … radiation/

An expensive and far off development using nuclear propulsion that is already controversial and would still only make the travel time 6 months(!)
This is a big reason why I argue for getting the propellant from the Moon. That way we would have virtually unlimited amount of propellant to drastically cut the travel time, no new expensive, (potentially) dangerous, far off propulsion systems required.
I estimate by using a Saturn V size vehicle with all hydrolox propulsion, launching from low lunar orbit or L2, we could make the trip in two weeks.

It's "the elephant in the room," NASA Chief Astronaut Robert Behnken
recently told a National Academy of Sciences committee.
"We're talking about a lot of ionizing radiation, almost a guarantee for
cancer, and you are really close to the edge of the range for lethal
exposure," said Kristin Shrader-Frechette, a University of Notre Dame
professor and a specialist in ethical issues that arise in scientific
research and technology development. "If we can't get shorter transit times
in space, and we can't get better shielding, then we really can't do (a
Mars) spaceflight."

The neutron spectrometer on Mars Odyssey detected hydrogen in the surface of Mars. It was estimated that space radiation (solar and GCR) that is the basis of this instrument had penetrated up to 1 metre. The Gamma Ray Spectrometer detected large chunks of ice. These instruments found a great deal of ice at or near the poles. However, there's practically none at or near the equator. There is a little at the bottom of ancient river channels, but you don't want to land in the bottom of a canyon. You want to land somewhere flat and smooth. You also want to send a human mission to some place relatively warm (not so cold). Ideal is near the equator, or at least between the lines of latitude that is the tropics. It feels odd talking about tropics on Mars, but it's the line of latitude that equals the axial tilt. Only one location has subsurface water, and flat/smooth, and tropical latitude. Unfortunately it's a high plateau, so relatively little atmosphere to protect against radiation. That's Meridiani Planum, where Opportunity landed. Opportunity examined the ground, and did not find obvious ice like Mars Phoenix did. Subsurface ice is not EVER going to be easy, so designing a mission to rely upon it is foolish.