A Realistic Interstellar Explorer

1.0 Introduction

"For more than 20 years, an “Interstellar Precursor Mission” has been discussed as a high priority for our understanding (1) the interstellar medium and its implications for the origin and evolution of matter in the Galaxy, (2) the structure of the heliosphere and its interaction with the interstellar environment, and (3) fundamental astrophysical processes that can be sampled in situ.

The chief difficulty with actually carrying out such a mission is the need for reaching significant penetration into the interstellar medium (~1000 Astronomical Units (AU1)) within the working lifetime of the initiators (50 years). During the last two years there has been renewed interest in actually sending a probe to another star system - a "grand challenge" for NASA - and the idea of a precursor mission has been renewed as a beginning step in a roadmap to achieve this goal.

Ongoing studies now being carried out by the Jet Propulsion Laboratory (JPL) in conjunction with a NASA-selected Interstellar Probe Science and Technology Definition Team (IPSTDT) are focused on the use of solar sails to achieve a more modest goal of ~400 AU in 20 years with a requirement of reaching at least 200 AU. This approach, as well as all of those previously considered, obtains significant solar-system escape speeds by “dropping” the probe into the Sun and then executing a DV maneuver at perihelion. In the solar sail approach, the sail is used first to remove the angular speed of the Earth and probe about the Sun; the sail is then maneuvered face-on into the Sun at 0.1 to 0.25 AU (set by sail thermal heating constraints), and solar radiation pressure accelerates the probe away from the Sun until the sail is jettisoned (at ~5 AU in the ongoing studies). The previous approaches, and that adopted for study here, initially send the probe out to Jupiter, using that planet's gravity to remove the probe angular momentum. The probe is then allowed to fall much closer to the Sun - in this case to 4 solar radii (RS 1) - where a large propulsive DV maneuver is required over a very short time - taken here to be ~15 minutes to minimize gravity losses. At this time all acceleration is over and the probe continues on a high-energy ballistic escape trajectory from the solar system.

In the scenario studied in our Phase I work, the use of a carbon-carbon thermal shield and an exotic propulsion system capable of delivering high specific impulse (Isp) at high thrust is enabling. For the NASA/JPL case, the manufacture, deployment, and management of long-term low-thrust maneuvering with a solar sail is the enabling propulsive technology. Both implementations require low-mass, highly integrated spacecraft in order to make use of moderate (Delta-class) expendable launch vehicles (ELVs). The further from the Sun that operation is required, the more stressing are the reliability requirements for the spacecraft itself. Our Phase I concept is baselined to operate at least 2.5 times as far from the Sun as the goal for the JPL study (1000 AU versus 400 AU) and contains system-architecture elements required as next-roadmap step after the sail mission - our probe design is largely independent of the propulsion means, whether those studied previously by us, solar sails, or others. In the Phase I work we have completed an initial scoping of the system requirements and have identified system drivers for actually implementing such a mission.

In this Phase I study we began the task of looking seriously at the spacecraft mechanical, propulsion, and thermal constraints involved in escaping the solar system at high speed by executing a DV maneuver close to the Sun. In particular, to fully realize the potential of this scenario, the required DV maneuver of ~10 to 15 km/s in the thermal environment of ~4 RS (from the center of the Sun) remains challenging. Two possible techniques for achieving high thrust levels near the Sun are: (1) using solar heating of gas propellant, and (2) using a scaled-down Orion (nuclear external combustion) approach. We investigated architectures that, combined with miniaturized avionics and miniaturized instruments, enable such a mission to be launched on a vehicle with characteristics not exceeding those of a Delta III. This systems approach for such an Interstellar Explorer has not been previously used to address all of these relevant engineering questions but is required to lead to (1) a probe concept that can be implemented following a successful Solar Probe mission (concluding around 2010), and (2) system components and approaches for autonomous operation of other deep-space probes within the solar system during the 2010 to 2050 time frame."

This paper is an excellent 30 minute read. The design of a Sun diver mission, used to greatly accelerate a spacecraft on an escape trajectory from the Solar System, is clearly very difficult. There are lots of challenges, including the question of how to protect the spacecraft from exposure to the environment within several radii of the Sun. Communication is another issue, as is weight savings. A spacecraft of only 50, 75, or 100 kg is required so that propulsion demands are not excessive. Even still, a change in velocity of 10 to 15 km/sec is required in a 15 minute interval. This is massive by normal standards, and will result in a 50 km/sec or greater escape velocity from the Sun. Burning within the gravity well of the Sun, after diving into the Sun from either Jupiter or the Earth, allows for a great amplification of the delta v rocket burn. Various methods could achieve the needed thrust, but not chemical rockets. Solar sails have always been an attractive alternative, as are ion propulsion systems, and nuclear pulse (orion type) rockets. In this paper, a method of collecting solar radiation (extremely powerful at this range) to heat a gas such as ammonia. Hydrogen would work better, but does not store well on long (ca 5 years) missions particularly when the heat on approach to the Sun is taken into account. This would be an ideal propulsion method because it can achieve the high ISP of ion propulsion, but also have higher thrust. Ion engines are not likely to burn quickly enough to work in only 15 minutes. In the end, only the solar-thermal option appears to work in a sun-diver mission. Perhaps this could be augmented with the use of solar sails in a hybrid mission.

Phase I Final Report - NASA Institute for Advanced Concepts: A Realistic Interstellar Explorer

Can a lighter-than-air spacecraft enter orbit?

Among many other relevant technologies, JP Aerospace is investigating the use of low thrust, high ISP ion thrusters to accelerate their spacecraft from near space to orbit. These are not traditional rockets made out of metal, but rather lighter-than-air spacecraft which float to high altitude (over 100,000 feet) and then slowly accelerate and climb to orbit using propellers and later plasma rockets. This kind of flight is slow, but also gentle and quite inexpensive once the system gets working. A minimal amount of fuel is required because much of the lift and propulsion is done using lift gas and solar power. When fuel is consumed, perhaps xenon for the plasma engines, it is burnt at a very high isp, so that only a few kg are required to orbit payloads. In addition to orbital craft, there are plans for massive high-altitude stations where astronauts can live for extended periods. Payloads can be held here for staging to orbital craft as well. Once in orbit, the craft can drop payload, and slowly return to the Earth. Because reentry is gradual, there may be ways to prevent the high-energy reentry with the requisite heat and deceleration. If this can be done, the spacecraft can reenter deep space, rendezvous with the large floating station, and pick up a new payload. Refueling can be accomplished by transferring minimal amounts, dozens of kg perhaps, of propellant.

See more about this specific project here.

Reaction research society two stage rocket

One problem with having over 1000 posts is that I can't remember if this is a repost or not. I think this rocket was mentioned previously, either while talking about the never flown 4 O 10,000 to 1 O 10,000 Kosdon project, or perhaps talking about Project Farside. If anyone can remember, post in the comments. Flying such a configuration helps if you want to stick to smaller, more reliable motors rather than giant motors of new design. This comes at the cost of reduced mass fractions and increased drag.

"On 17 October, 2009 a two stage rocket consisting of a cluster of four standard RRS “class” motors in the first stage and a single “class” motor for the second stage (Figure 1) was flown at the Mojave Test Area. Pre-flight modeling suggested a peak altitude of about 45,000 feet and a maximum velocity of about Mach 2.5. Available data indicate that a partial failure of the nose cone attachment resulted in “cocking” of the nose cone and subsequent “coning” of the vehicle as it accelerated. The coning in turn resulted in a trajectory that headed approximately southeastwardly rather than in the planned southwest (downrange) direction. Analysis of video of the second stage burn allows the performance of the rocket to be constrained to a probable burnout velocity above 1700 feet / second at about 6900 feet altitude. Six DOF modeling suggests a maximum altitude of at least 13,000 feet."

More here.

Vesta!

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Project High Jump Boosted Dart

How do I always miss the great projects?

Here is video footage of the attempt:



The motor failed during burn, resulting in a shred and recovery failures. This flight was one of several proposed Carmack 100kft projects. You can read more about these projects here.

The specs for Project High Jump are:

Boosted Dart configuration
4" dia 36,000ns Booster
Case bonded
Double Taper Core
Booster 7' 4" Overall length
Welded Fin Can

Dart Configuration
1.5" dia
40" Length
Fins Welded to tube

Raven Altimeters in booster and Dart
Big Red Bee 2 meter high power GPS telemetry

A boosted dart is a small, dense dart that is attached to a larger booster. On burnout the dart flies free, and is optimally designed to coast very well. Darts are dense, thin, and usually have a boat tail on the bottom. Boat tails greatly reduce base drag in the lower atmosphere, and are something like a backwards nosecone. When a rocket has a built-in motor, there is severe base drag because the bottom is typically a flat, abrupt ending to the rocket.

Boosted dart apogees can be twice as high as a regular rocket of similar impulse, perhaps higher. In one example, the Reaction Research Society (RRS) launched an R motor boosted dart that hit nearly 100 KM altitude despite burning out at about 10,000 feet. That tiny dart coasted at 4,500 fps in dense lower atmosphere, yet almost made space despite that. The dart coasted for about 50 miles! A full-sized R motor would have been lucky to get as high as 100,000 feet if it had to fly as one unit simply because drag is so serious at low altitude. By comparison, rockets typically need to hit mach 5 and 40,000 feet to get space. Darts can do it from miles lower.

It is logical to use a boosted dart for a "simple" goal like getting electronics over 100,000 feet. It is cheaper than a giant motor (the Q motor that did break 100,000 feet) and less complex than a two stage rocket. The N5800 motor is a bit slow burning for a dart, but it would certainly be enough to get a dart above 100,000 feet under the right conditions. In this case, the booster was a thin O motor that could have done a bit better than the N5800, but reliability matters also.

More images here

Solid Propellant Burn Rate Enhancement in Rocketry

A REVIEW OF SOLID PROPELLANT BURN RATE ENHANCEMENT BY MECHANICAL METHODS

DAVID REESE

Abstract. The inclusion of metal fibers in a solid propellant grain has been shown to increase its bulk burning rate dramatically, and is a technology that was applied in several early sounding rockets. This review covers historical and current applications for the technology, as well as the theoretical basis for burning rate enhancement. Though technically successful, the use of wires to achieve high burning rates has largely been replaced with the use of reactive catalysts and other high burning rate energetic materials. However, recent concern over the sensitivity of such propellants is generating interest in other means of accelerating burn rates. As such, several practical research topics involving wire enhancement of burning rates are presented to reintroduce this technology into the motor designer’s toolbox.

TDK Propulsion

http://www.aame.in/

Aerospace news from India

1959 - Missile designed with HITCO in mind!

Thing is, this missile has a very strange design including "blast tubes" and plastic fins.

On Ebay Now

Test your vision

Try the test

RS-25 SSME

The Libya Rocketry Association

"I am working on a plan to make (tourist rocket sport) in Libya and open the door for the world amateur rocketry to come over and shoot their rockets with me on the Libyan desert and by the sea side..."

I have to admit that I get bad flashbacks when I think about amateur rockets in Libya considering the violence last year, not to mention the typical role of rockets in northern Africa, but if the goals of this association are to practice rocketry for the sake of science and exploration, it is a good thing. Before I hold Libya to excessively high standards, let's not forget that American rocketry started (and remains) largely a military matter. Maybe if more people flew rockets for hobby, the World would be better.

http://rocketlibyan.blogspot.com/

Post number 1000

Despite being around for many years, this blog has only today arrived at the 1000th post. Most of these posts have come in just the last three years. Thanks to all the loyal readers; without your interest, the minuscule Google payments alone would not justify maintaining a regular post rate. The picture above may perhaps be the best in the history of rocketry. It is a 4 stage, 10 motor rockoon, accelerating with something like a 75 to 1 thrust ratio on it's way to space. The rocket has just flown directly through a giant helium balloon, piercing it in two places the way a bullet would pass through a soap bubble. The rocket is so fast that the balloon has not yet collapsed. This image encompasses all that is great about rocketry. The farside project was complex, risky, expensive, and damn fast. The upper stage was expected to hit more than 17,000 mph, and top out at an apogee of thousands of miles. That giant balloon contained 3.75 million cubic feet of lift gas. After getting this rockoon to work, there was a tentative plan to use an extra stage to launch payloads at the Moon!

This is the substance of rocketry. This is why rocketry and space exploration will always have a central place in my life. In other words, get ready for the next thousand posts. Soon enough, I will start a new rocket project and attempt level 2 certification in the spring.

Just because this picture is so great, I decided to throw in a Hayden Planetarium (the sphere within the glass building) for scale. It is a bit less than half the diameter, and 1/10th the volume of the balloon used for this project. (Spheres are so strange.)

You can read more about Project Farside here, here, and here.

March to the Moon image archive

Gemini images
Mercury images

Google+ Hangout: Phobos-Grunt re-entry

On January 15, 2012, the Russian spacecraft Phobos-Grunt re-entered over the Pacific ocean and burned up. During this time, I reported the event live with Planetary Society science journalist Emily Lakdawalla on a Google+ Hangout.

So what has Phobos-Grunt been up to?



The final landing zone was in the Pacific. If you were the gambling sort you would tend to guess the Pacific for any object crashing into the Earth simply because it is the largest single target. On an unrelated note, if you are the gambling sort and want to borrow money at 10 points vig per week, let me know.

Onboard footage from N altitude flight

Video footage - lots of spin!

I bet this rocket would have broken 50,000 feet, possibly 10 miles even, without the conning and spin.

Phobos Grunt has crash-landed back to Earth

The odds of recovering any pieces are slim.

Phobos-Grunt plunged to Earth into the Pacific Ocean on Jan 15, 2012 - Predicted Crash Zone

Maps shows orbital track of Phobos-Grunt on Final Orbit before crashing to Earth in the Pacific Ocean west of South America on Jan 15, 2012. Atlantic Ocean was at the center of the predicted crash zone after fiery reentry of Russia’s Phobos Grunt spacecraft. Credit: Roscosmos

The Restart Page - Reboot under different OSes

http://www.therestartpage.com/

Soviet lunar landing

Giant Leap Mariah 38 on Ebay

This is very tempting, particularly to buy and use for my first dual deploy experiments, but even a lowball offer ($120) seems like too much. I plan to build a level 2 cert rocket next month - and it will be a 3" x 78" all fiberglass rocket for a total cost of about $140.

Ebay Listing - ending in only 9 hours.

Saturn V